The chemistry of Au(I) complexes with two types of cyclic (alkyl)(amino)carbene (CAAC) ligands has been explored, using the sterically less demanding dimethyl derivative Me2CAAC and the 2-adamantyl ligand AdCAAC. The conversion of (AdCAAC)AuCl into (AdCAAC)AuOH by treatment with KOH is significantly accelerated by the addition of tBuOH. (AdCAAC)AuOH is a convenient starting material for the high-yield syntheses of (AdCAAC)AuX complexes by acid/base and C-H activation reactions (X = OAryl, CF3CO2, N(Tf)2, C2Ph, C6F5, C6HF4, C6H2F3, CH2C(O)C6H4OMe, CH(Ph)C(O)Ph, CH2SO2Ph), while the cationic complexes [(AdCAAC)AuL]+ (L = CO, CN t Bu) and (AdCAAC)AuCN were obtained by chloride substitution from (AdCAAC)AuCl. The reactivity toward variously substituted fluoroarenes suggests that (AdCAAC)AuOH is able to react with C-H bonds with pKa values lower than about 31.5. This, together with the spectroscopic data, confirm the somewhat stronger electron-donor properties of CAAC ligands in comparison to imidazolylidene-type N-heterocyclic carbenes (NHCs). In spite of this, the oxidation of Me2CAAC and AdCAAC gold compounds is much less facile. Oxidations proceed with C-Au cleavage by halogens unless light is strictly excluded. The oxidation of (AdCAAC)AuCl with PhICl2 in the dark gives near-quantitative yields of (AdCAAC)AuCl3, while [Au(Me2CAAC)2]Cl leads to trans-[AuCl2(Me2CAAC)2]Cl. In contrast to the chemistry of imidazolylidene-type gold NHC complexes, oxidation products containing Au-Br or Au-I bonds could not be obtained; whereas the reaction with CsBr3 cleaves the Au-C bond to give mixtures of [AdCAAC-Br]+[AuBr2]- and [(AdCAAC-Br)]+ [AuBr4]-, the oxidation of (AdCAAC)AuI with I2 leads to the adduct (AdCAAC)AuI·I2. Irrespective of the steric demands of the CAAC ligands, their gold complexes proved more resistant to oxidation and more prone to halogen cleavage of the Au-C bonds than gold(I) complexes of imidazole-based NHC ligands.
The chemistry of nclass="Chemical">Au(I)class="Chemical">n class="Chemical">complexes with two types of cyclic (alkyl)(amino)carbene(CAAC) ligands has been explored, using the sterically less demanding dimethyl derivativeMe2CAAC and the 2-adamantyl ligand AdCAAC. The conversion of (AdCAAC)AuCl into (AdCAAC)AuOH by treatment with KOH is significantly accelerated by the addition of tBuOH. (AdCAAC)AuOH is a convenient starting material for the high-yield syntheses of (AdCAAC)AuX complexes by acid/base and C-H activation reactions (X = OAryl, CF3CO2, N(Tf)2, C2Ph, C6F5, C6HF4, C6H2F3, CH2C(O)C6H4OMe, CH(Ph)C(O)Ph, CH2SO2Ph), while the cationic complexes [(AdCAAC)AuL]+ (L = CO, CN t Bu) and (AdCAAC)AuCN were obtained by chloride substitution from (AdCAAC)AuCl. The reactivity toward variously substituted fluoroarenes suggests that (AdCAAC)AuOH is able to react with C-H bonds with pKa values lower than about 31.5. This, together with the spectroscopic data, confirm the somewhat stronger electron-donor properties of CAAC ligands in comparison to imidazolylidene-type N-heterocycliccarbenes (NHCs). In spite of this, the oxidation of Me2CAAC and AdCAAC goldcompounds is much less facile. Oxidations proceed with C-Au cleavage by halogens unless light is strictly excluded. The oxidation of (AdCAAC)AuCl with PhICl2 in the dark gives near-quantitative yields of (AdCAAC)AuCl3, while [Au(Me2CAAC)2]Cl leads to trans-[AuCl2(Me2CAAC)2]Cl. In contrast to the chemistry of imidazolylidene-type gold NHCcomplexes, oxidation products containing Au-Br or Au-I bonds could not be obtained; whereas the reaction with CsBr3 cleaves the Au-C bond to give mixtures of [AdCAAC-Br]+[AuBr2]- and [(AdCAAC-Br)]+ [AuBr4]-, the oxidation of (AdCAAC)AuI with I2 leads to the adduct (AdCAAC)AuI·I2. Irrespective of the steric demands of the CAAC ligands, their gold complexes proved more resistant to oxidation and more prone to halogen cleavage of the Au-C bonds than gold(I) complexes of imidazole-based NHC ligands.
Lappert’s pioneering
work in the early 1970s established
N-nclass="Species">donor-stabilized class="Chemical">n class="Chemical">carbenes as remarkably versatile ligands across
the Periodic Table, particularly for noble metals, and demonstrated
the similarity of the coordination chemistry of N-heterocycliccarbenes
(NHCs) and phosphines.[1−3] This work also included the first examples of gold
NHCcomplexes, the dimethylimidazolidinylidene derivatives [Au{C(NMe)2C2H4}2]X (X = Cl, BF4).[4] Since then, N-heterocycliccarbenes have become one of the most successful and adaptable ligand
classes in organometallic chemistry.[5]
A related type of saturated 5-ring nclass="Chemical">carbene ligaclass="Chemical">nds is the family
of class="Chemical">n class="Chemical">cyclic (alkyl)(amino)carbenes (CAACs) developed by Bertrand et
al.,[6] which were inter alia found capable
of stabilizing complexes of zerovalent gold,[7] while gold(I) CAACcomplexes act as catalysts for a range of interesting
transformations.[8] These ligands show electron
affinities more negative than those of the more widely used unsaturated
imidazolin-2-ylidene type carbenes and higher ligand-to-metalcharge
transfer ΔN values; i.e., CAAC ligands behave
as stronger σ donors.[9]
On the
other hand, it is benclass="Chemical">comiclass="Chemical">ng appareclass="Chemical">nt that, eveclass="Chemical">n with class="Chemical">n class="Chemical">NHC
ligands, the π-acceptor capacity has an important influence
on reactivity.[10−13] As Ciancaleoni et al. showed recently,[14] in contrast to the general description of NHCs as strong σ-donors,
in the case of gold they donate less strongly than phosphines, and
for this metal in particular there is a significant difference between
NHCs with saturated and unsaturated rings; i.e. the π-acceptor
capability is likely to play an important role.[11−13] With this in
mind, we became interested in exploring the reactivity patterns of
CAAC-type carbenes, and their possible differences in comparison to
more conventional types of NHCs. We report here an exploration of
the reactivity of CAAC goldcomplexes, including oxidation reactions
to Au(III)compounds. Two types of CAAC ligands were employed: the
sterically less demanding dimethyl derivativeMe2CAAC and
the 2-adamantyl ligand AdCAAC (Chart I).[6]
Chart I
Results and Discussion
Although
nclass="Chemical">gold(I) chloride class="Chemical">n class="Chemical">complexes LAuCl are most commonly employed
as entries into ligand exchange reactions and catalytic transformations,
often in combination with silver salts, it can be synthetically advantageous
to substitute the chloride ligand for a more labile oxygen-containing
ligand, so that subsequent reactions benefit from the relative weakness
of the Au–O bond.[15] We therefore
decided to prepare the corresponding CAACgold(I) alkoxides, hydroxides,
and carboxylates.
Anion Exchange Reactions
The reaction
of nclass="Chemical">(AdCAAC)AuCl (1) with class="Chemical">n class="Chemical">sodium tert-butoxide
in toluene generates the white alkoxidecomplex (AdCAAC)AuOBu (2) in essentially quantitative
yield (Scheme 1).[16] The alkoxide is very sensitive to hydrolysis, and the reaction must
be conducted in anhydrous solvents under inert gas. Treatment of 2 with water readily produces the air-stable hydroxide (AdCAAC)AuOH (3). Complex 3 is characterized
in its 1H NMR spectrum by a broadened singlet of the OH
ligand at δ −0.29 ppm (in C6D5Br).
Scheme 1
The same product is also accessible directly from the
reaction
between the nclass="Chemical">chloride 1 aclass="Chemical">nd class="Chemical">n class="Chemical">KOH; however, this reaction
proved to be very slow, requiring over 48 h to achieve a 75% conversion.
On the other hand, we found that the addition of BuOH to the mixture significantly accelerates the rate of chloride
substitution and generates the hydroxide 3 cleanly within
24–36 h, evidently due to equilibrium concentrations of strongly
nucleophilic BuO–,
which catalyzes chloride substitution.[17] The use of CsOH, which is often found preferable in gold chloride
substitution reactions, is therefore unnecessary. Both complexes 2 and 3 are soluble in polar and aromatic organic
solvents (THF, toluene, 1,2-difluorobenzene) and insoluble in hexanes.
Chlorinated solvents (CHCl3, CH2Cl2, and 1,2-dichloroethane) should be avoided, because their presence
tends to lead to the regeneration of the gold chloride. While the
hydroxide 3 can be stored at room temperature in air
for months, the tert-butoxide 2 is very
sensitive to hydrolysis and has to be kept under an inert atmosphere.
The carbene-C resonance in the 13C NMR spectra of 2 and 3 is observed at δ 238, slightly
upfield from the chloride precursor complex (AdCAAC)AuCl
(δ 239.9).
During reactions of 3 with nclass="Chemical">p-methoxyacetophenone
(vide iclass="Chemical">nfra), a small crop of crystals of a class="Chemical">n class="Chemical">condensation product of 3 was also obtained, the O-bridged cluster [{(AdCAAC)Au}3(μ3-O)]+OH–. This compound was identified crystallographically (see the Supporting Information, Figure S9). It is analogous
to the well-known Nesmeyanov cation,[18] and
its formation indicates that, in spite of the steric bulk of AdCAAC, condensation of the hydroxide can still take place.[19]
Both (nclass="Chemical">AdCAAC)class="Chemical">n class="Chemical">AuOBu (2) and (AdCAAC)AuOH (3) react cleanly
with arylboronic acids in toluene under neutral conditions, i.e. without
the addition of external bases, to give the corresponding gold aryls,
exemplified here by the quantitative formation of (AdCAAC)Au(p-C6H4F) (4; see Scheme 1). Neutral conditions have been shown to be preferable
for reactions of boronic acids with both Au(I)[20] and Au(III)[21] hydroxides and
to lead cleanly to the corresponding gold organyl complexes in excellent
yields.
The reaction of 3 with trifluoroacetic
acid (nclass="Chemical">tfaH)
affords (class="Chemical">n class="Chemical">AdCAAC)Au(tfa) (5). This product
is also accessible directly from (AdCAAC)AuCl and Ag(tfa).
Both methods give essentially quantitative yields; however, the latter
approach contaminates the desired complex with traces of silver salts.
The carbene carbon resonance is observed at δ(13C)
232.4. This upfield shift of the carbene13C signal in
comparison to that of the chlorocomplex is observed for all the complexes
with Au–O bonds described here but is particularly pronounced
for the trifluoroacetate. Complex 5 proved to be temperature
sensitive and should be stored at −30 °C to avoid darkening
of the sample.
The nclass="Chemical">hydroxide 3 is a class="Chemical">n class="Chemical">convenient
starting material
for the preparation of gold aryloxides and reacts with 3,5-di-tert-butylphenol to give the corresponding gold phenolatecomplex 6 in high yield. This synthetic method offers
advantages over salt metathesis approaches, since reactions can be
carried out in air and isolation of analytically pure products is
straightforward. Complex 6 was isolated as a white stable
solid which can be handled in air for weeks and is stable in toluene
solution for months without noticeable decomposition. Like the hydroxide
and alkoxidecompounds, 6 is sensitive to chlorinated
solvents; therefore, such solvents have to be avoided. The 13C carbene-C resonance is observed at δ 236.1 (in C6D6).
The reaction of the nclass="Chemical">gold hydroxide 3 with class="Chemical">n class="Chemical">HNTf2 in toluene is a high yield route to the Gagosz-type[22] complex (AdCAAC)AuNTf2 (7), which is of interest for silver-free protocols
in gold catalysis.[23] Complex 7 is an air-stable white solid which is soluble in all polar organic
solvents. The carbene resonance was observed at δ 233.8. The
molecular structure of 7 is shown in Figure 1. The complex is linear; the Au–N and Au–C
bond lengths fall in the ranges of 2.077(3)–2.094(3) and 1.969(2)–1.985(2)
Å, respectively, similar to those for previously reported (NHC)AuNTf2complexes.[22]
Figure 1
Crystal structures of
(left) (AdCAAC)AuNTf2 (7) and (right)
(AdCAAC)AuC6HF4 (11).
Ellipsoids are shown at the 50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): complex 7, Au–C(1)
1.977(4), Au–N(2) 2.098(3), N(2)–S(1) 1.627(4), C(1)–C(2)
1.528(5), C(1)–N(1) 1.315(5), C(1)–Au–N(2) 178.64(16),
S(1)–N(2)–Au 119.48(19); complex 11, Au–C(1)
2.018(3), Au–C(28) 2.038(3), C(1)–C(2) 1.528(4), C(1)–N(1)
1.301(4), C(1)–Au–C(28) 177.54(11).
Crystal structures of
(left) (class="Chemical">AdCAAC)class="Chemical">n class="Chemical">AuNTf2 (7) and (right)
(AdCAAC)AuC6HF4 (11).
Ellipsoids are shown at the 50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): complex 7, Au–C(1)
1.977(4), Au–N(2) 2.098(3), N(2)–S(1) 1.627(4), C(1)–C(2)
1.528(5), C(1)–N(1) 1.315(5), C(1)–Au–N(2) 178.64(16),
S(1)–N(2)–Au 119.48(19); complex 11, Au–C(1)
2.018(3), Au–C(28) 2.038(3), C(1)–C(2) 1.528(4), C(1)–N(1)
1.301(4), C(1)–Au–C(28) 177.54(11).
C–H Activation Reactions
The basicity of (nclass="Chemical">AdCAAC)class="Chemical">n class="Chemical">AuOH may be exploited to activate C–H bonds.
Phenylacetylene and diethyl malonate give the corresponding metalation
products (AdCAAC)AuC≡CPh (8) and (AdCAAC)AuCH(CO2Et)2 (9),
respectively (see Scheme 2). Compounds 8 and 9 are white solids, stable in air at room
temperature. Bertrand has previously reported the synthesis of complex 8 in the reaction of (AdCAAC)AuCl with the lithium
salt of phenylacetylene.[8a] The hydroxide
route allows the synthesis of 8 by a simpler procedure
in air.
Scheme 2
Syntheses of Gold(I) AdCAAC Complexes
Reaction conditions: (i) Htfa,
toluene, 23 °C, 4 h; (ii) toluene, 23 °C, 18 h; (iii) toluene,
60 °C, 18 h; (iv) toluene, 80 °C, 18 h; (v) 1,4-dioxane,
75 °C, 18 h; (vi) toluene, 70 °C, 12 h; (vii) toluene, 70
°C, 18 h.
Syntheses of Gold(I) AdCAAC Complexes
Reactionclass="Chemical">coclass="Chemical">nditioclass="Chemical">ns: (i) class="Chemical">n class="Chemical">Htfa,
toluene, 23 °C, 4 h; (ii) toluene, 23 °C, 18 h; (iii) toluene,
60 °C, 18 h; (iv) toluene, 80 °C, 18 h; (v) 1,4-dioxane,
75 °C, 18 h; (vi) toluene, 70 °C, 12 h; (vii) toluene, 70
°C, 18 h.
The reactivity of 3 toward a series of nclass="Chemical">fluorobenzenes
with decreasiclass="Chemical">ng degrees of F substitutioclass="Chemical">n eclass="Chemical">nables the pKa value of the class="Chemical">n class="Chemical">gold hydroxide to be estimated. The pKa values of a range of fluoroarenes have been
calculated,[24] with values of 29.0 and 23.1
for C6HF5 and 1,2,4,5-C6H2F4, respectively. As expected, 3 reacts with
pentafluorobenzene at 60 °C and with 1,2,4,5-tetrafluorobenzene
at 80 °C to give the corresponding aryl complexes (AdCAAC)AuC6H5–F (10, n = 5; 11, n = 4) in essentially quantitative yields
(see Scheme 2). The structure of (AdCAAC)AuC6HF4 is shown in Figure 1. The Au–C(carbene) and Au–C(aryl) bond lengths
are similar to those reported in the analogous complex (NHC)AuC6H2F3 (2.026(3) and 2.044(3) Å).[25]
Prolonged heating with the less C–H
acidicnclass="Chemical">1,3,5-trifluorobenzene
(pKa ≈ 31.5) also leads to the
formatioclass="Chemical">n of the class="Chemical">n class="Chemical">corresponding gold aryl complex (AdCAAC)Au(2,4,6-C6H2F3) (12); however, the
reaction is slow and the product was contaminated with unreacted hydroxide 3. A higher temperature of 90 °C accelerated the gold
arylation, but according to the 19F NMR spectrum this was
accompanied by some decomposition. The new set of resonances for fluorine
atoms in the 19F NMR spectrum was detected as multiplets
centered at δ −84.60 (2F) and −116.86 (1F). To
prove that these multiplets corresponded to the desired complex 12, we performed the auration of 1,3,5-trifluorobenzene with
the more basic (AdCAAC)Au(OBu), generated in situ from (AdCAAC)AuCl and NaOBu (eq 1). These mixtures proved
more reactive than pure isolated 3 and gave the desired
complex 12 in 49% yield. The formation of 12 is accelerated by higher temperatures (75 °C), but since the tert-butoxide 2 is somewhat temperature sensitive,
its slow decomposition may explain the reduced yield.
The nclass="Chemical">auratioclass="Chemical">n of class="Chemical">n class="Chemical">1,3,5-trifluorobenzene by 3 and
(AdCAAC)AuCl/NaOBu mixtures
is
in contrast with the lack of reactivity of (IPr)AuOH[23] and is an indication for the enhanced basicity provided
by the CAAC ligand. On the other hand, no reaction was observed with
1,2-difluorobenzene and with monofluorobenzene. The reactivity decreases
therefore in the sequence shown in Scheme 3;[24] evidently (AdCAAC)AuOH
is sufficiently basic to undergo reactions with C–H bonds with
pKa values of 31.5 or less. This reactivity
places the (CAAC)AuOHcomplexes closer to that of Larossa’s
systems (Bu3P)AuCl/AgSbF6 and (R3P)AuCl/NaOtBu, which also aurate
1,3,5-trifluorobenzene.[25]
Scheme 3
The nclass="Chemical">hydroxide 3 is a class="Chemical">n class="Chemical">convenient
starting material
for the metalation of a series of functionalized C–H compounds.
For example, the reaction of (AdCAAC)AuOH with p-methoxyacetophenone, deoxybenzoin, and methyl phenyl
sulfone gave the corresponding gold alkyls (AdCAAC)AuR
(R = CH2C(O)C6H4OMe (13), CH(Ph)C(O)Ph (14) and CH2SO2Ph (15); see Scheme 2). Related
α-keto alkyls have previously been postulated as catalytic intermediates,
e.g. Pd–CH(Ph)C(O)Ph species, in the α,α-diarylation
of acetophenone en route to tamoxifen precursors.[26] The reaction of 3 with acetophenone has a
precedence in the formation of (Ph3P)Au-CH2C(O)Ph
from acetophenone and Nesmeyanov’s [Au3(μ3-O)(PPh3)3]+ cation,[27] while more recent alternative syntheses of gold
α-keto alkyls have involved the use of silyl enolates with (Ph3P)AuCl/CsF reagents.[28,29]
The C–H
activated products 8–15 were isolated
as white air-stable solids which are soluble in all
nclass="Chemical">commoclass="Chemical">n orgaclass="Chemical">nic solveclass="Chemical">nts, with the exceptioclass="Chemical">n of class="Chemical">n class="Chemical">alkanes. Unlike the
other compounds, the deoxybenzoin gold complex 14 possesses
very low solubility in benzene and toluene. The resonances of the
gold methine proton for 9 and 14 and of
the gold methylene protons for 13 and 15 are shifted downfield by 1–2 ppm in the 1H NMR
spectra in comparison to the signals for the free ligands. The 13C carbene-carbon resonances for 8–15 are shifted upfield relative to those for (AdCAAC)AuCl and are observed in the range δ 253.2–260.2.
The Au-CHR1R2 center in the C1-symmetric complex 14 is chiral; the complex
therefore shows two sets of resonances related to the AdCAAC ligand in its 1H NMR spectrum, since the CH2 and CMe2 moieties of the CAAC ligand are diastereotopic
(see the Supporting Information). This
is illustrated by the crystal structure of complex 14 (Figure 2), which shows that the isopropyl
group C(14)–C(15)–C(16) occupies a position almost above
the phenyl ring of deoxybenzoin (C36–C41), with atom C(15)
oriented toward the phenyl ring plane (3.747(8) Å). This spatial
orientation of C(15) explains the high-field 1H NMR chemical
shift of this methyl group, at δ 0.89, due to magnetic shielding
by the aryl.
Figure 2
Crystal structure of (AdCAAC)Au(deoxybenzoinyl)
(14). Ellipsoids are shown at the 50% probability level.
Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au–C(1) 2.039(4), Au–C(28) 2.142(4), C(1)–C(2)
1.522(6), C(1)–N(1) 1.308(6), O(1)–C(29) 1.240(6), C(29)–C(28)
1.465(7), C(29)–C(30) 1.527(6), C(28)–C(36) 1.514(6),
C(1)–Au–C(2) 176.89(14).
Crystal structure of class="Chemical">(AdCAAC)Au(deoxybenzoinyl)
(14). Ellipsoids are showclass="Chemical">n at the 50% probability level.
class="Chemical">n class="Chemical">Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au–C(1) 2.039(4), Au–C(28) 2.142(4), C(1)–C(2)
1.522(6), C(1)–N(1) 1.308(6), O(1)–C(29) 1.240(6), C(29)–C(28)
1.465(7), C(29)–C(30) 1.527(6), C(28)–C(36) 1.514(6),
C(1)–Au–C(2) 176.89(14).
Functionalized alkyl nclass="Chemical">complexes such as 13–15 should, iclass="Chemical">n priclass="Chemical">nciple, provide access to α-keto class="Chemical">n class="Chemical">carbenes,
which have been suggested as elusive transient intermediates in a
number of organic transformations.[30] Preliminary
tests have shown, however, that these complexes do not undergo α-hydride
abstraction with standard electrophiles such as CPh3+ salts. Methods for generating functionalized gold carbenecomplexes are currently being investigated.
CO, CN, and Alkene Complexes
The reaction of 1 with nclass="Chemical">silver salts iclass="Chemical">n the preseclass="Chemical">nce
of class="Chemical">n class="Chemical">CO or BuNC gives the corresponding
cationic complexes [(AdCAAC)Au(L)]+ (L = CO
(16); L = BuNC (17)), which were isolated
as SbF6– salts in high yields (Scheme 4). Complexes 16 and 17 are white solids, soluble in low-coordinating polar organic solvents
(CH2Cl2, 1,2-difluorobenzene). Coordinating
solvents such as acetone lead to immediate CO effervescence. All complexes
are stable in air, but the carbonyl 16 has to be stored
under a CO atmosphere.
Scheme 4
The IR spectrum of 16 shows the nclass="Chemical">CO stretchiclass="Chemical">ng viclass="Chemical">n class="Chemical">bration
at 2183 cm–1. As is characteristic for COcomplexes
of gold ions, the CO stretching frequency is higher than that of free
CO (2143 cm–1). The CO stretch of 16 falls within the range observed for COcomplexes of Au(I) with phosphine
and carbene ligands;[14,31] for instance, the ν(CO)
value of 16 is marginally lower than those of [(Mes3P)Au(CO)][SbF6] (Mes = 2,4,6-C6H2Me3) and [(SIDipp)Au(CO)][SbF6], (by
2 and 14 cm–1, respectively).[31] Similarly, the IR spectrum of the isonitrilecomplex 17 displays a strong vibration at 2241 cm–1 which is blue-shifted in comparison to the signal for free tert-butyl isocyanide (2135 cm–1) and
almost identical with that of [(SIDipp)Au(CNtBu)][SbF6] (2244 cm–1).[31]
The cyano nclass="Chemical">complex (class="Chemical">n class="Chemical">AdCAAC)AuCN (18) was
prepared for comparison with the COcompound, by reaction of the hydroxide
(AdCAAC)AuOH with Me3SiCN or of that of (AdCAAC)AuCl and KCN. Both approaches lead to almost quantitative
yields of complex 18. The complex shows a νCN frequency of 2140 cm–1. The C–N
frequency of cyanide anions is relatively insensitive to the nature
of the ligand in a trans position, and the value is close to that
observed for a range of gold(I) CN complexes with phosphine and carbene
ligands. There was no ligand rearrangement to give [Au(CN)2]− salts, as seen for [Au(PMes3)2][Au(CN)2] prepared by the (Mes3P)AuCl/KCN
route.[31] Complex 18 is stable
in air and soluble in all polar organic solvents.
The nclass="Chemical">1H NMR spectra show that the chemical shifts for
the class="Chemical">n class="Chemical">CAAC-CH2 protons in the five-membered rings of 16–18 are about 0.3–0.8 ppm upfield
of that of (AdCAAC)AuCl. The carbene-C resonances for 16–18 are observed at δ 241.1, 246.2,
and 253.1, respectively. The CO 13C signal of 16 (δ 182.4) is almost identical with that of [(SIDipp)Au(CO)][SbF6] (δ 182.7). The tert-butyl isocyanide CNC(CH3)313C shifts of 17 are observed at δ 142.4 and 58.6,
broadened by bonding to quadrupolar 14N. 18 shows a 13CN resonance at δ 149.5,
slightly shifted upfield of that of (SIDipp)AuCN (δ 152.4).[31] Overall, therefore, these data suggest that
the electronic characteristics of CAAC ligands are generally comparable
to those of saturated imidazolidinylidene-type NHCs.
The crystal
structures of the nclass="Chemical">CO, BuCN, aclass="Chemical">nd CN class="Chemical">n class="Chemical">complexes
are shown in Figure 3. The carbonyl complex 16 shows the greatest deviation
from linear geometry: C(1)–Au–C(28) 172.9(4)°.
The Au–C(28) bond trans to the CAAC ligand elongates from 1.964(5)
Å for the COcomplex 16 to 2.017(5) Å for the
cyanide 18, whereas the carbene–Au distances remain
approximately constant throughout this series, deviating only slightly
from the value of 2.031(5) Å observed for the cyanide 18. The isonitrilecomplex 17 crystallized with a molecule
of 1,2-difluorobenzene, which exhibits a T-shaped C–F···π
intermolecular interaction between carbon C(28) and one of the fluorine
atoms of 1,2-difluorobenzene (C(28)···F(8) 3.090(3)
Å), which falls into the range of intermolecular interactions
of 2.99–3.53 Å observed for various fluoro-organic compounds.[32]
Figure 3
Solid-state structures of the cations in (left to right)
[(AdCAAC)Au(L)]SbF6 (L = CO (16), BuNC (17)) and (AdCAAC)AuCN (18). Ellipsoids are shown at the
50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): 16, Au–C(1) 2.035(4),
Au–C(28) 1.964(5), C(28)–O(1) 1.108(6), C(1)–C(2)
1.519(6), C(1)–N(1) 1.290(5), C(1)–Au–C(28) 173.97(17),
Au–C(28)–O(1) 172.9(4); 17, Au–C(1)
2.022(2), Au–C(28) 1.986(3), C(28)–N(2) 1.143(3), N(2)–C(29)
1.467(3), C(1)–C(2) 1.525(3), C(1)–N(1) 1.304(3), C(1)–Au–C(28)
175.05(9), Au–C(28)–N(2) 174.2(2), C(28)–N(2)–C(29)
177.5(2); 18, Au–C(1) 2.031(5), Au–C(28)
2.017(5), C(28)–N(2) 1.127(6), C(1)–C(2) 1.516(7), C(1)–N(1)1
1.316(5), C(1)–Au–C(28) 177.33(16), Au–C(28)–N(2)
176.4(5).
Solid-state structures of the cations in (left to right)
[(class="Chemical">AdCAAC)class="Chemical">n class="Chemical">Au(L)]SbF6 (L = CO (16), BuNC (17)) and (AdCAAC)AuCN (18). Ellipsoids are shown at the
50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): 16, Au–C(1) 2.035(4),
Au–C(28) 1.964(5), C(28)–O(1) 1.108(6), C(1)–C(2)
1.519(6), C(1)–N(1) 1.290(5), C(1)–Au–C(28) 173.97(17),
Au–C(28)–O(1) 172.9(4); 17, Au–C(1)
2.022(2), Au–C(28) 1.986(3), C(28)–N(2) 1.143(3), N(2)–C(29)
1.467(3), C(1)–C(2) 1.525(3), C(1)–N(1) 1.304(3), C(1)–Au–C(28)
175.05(9), Au–C(28)–N(2) 174.2(2), C(28)–N(2)–C(29)
177.5(2); 18, Au–C(1) 2.031(5), Au–C(28)
2.017(5), C(28)–N(2) 1.127(6), C(1)–C(2) 1.516(7), C(1)–N(1)1
1.316(5), C(1)–Au–C(28) 177.33(16), Au–C(28)–N(2)
176.4(5).
In view of our earlier observation
that nclass="Chemical">ethylene iclass="Chemical">nserts iclass="Chemical">nto class="Chemical">n class="Chemical">Au(III)–trifluoroacetate
bonds to give the functionalized alkyls Au–C2H4OAcF,[33] (AdCAAC)AuOAcF was exposed to an atmosphere of ethylene for
extended periods of time, either in CH2Cl2 with
the addition of AgOAcF as catalyst or in CH2Cl2/HOAcF mixtures. However, no insertion of
ethylene was observed. The intermediate in this insertion reaction
is a cationic alkenecomplex, and such a complex is indeed easily
accessible from the trifluoroacetate precursor if B(C6F5)3 is added as the anion acceptor, as exemplified
by the norbornenecomplex 19 (Scheme 5). The compound is a white, air-stable solid which is soluble
in polar organic solvents. The carbene-C signal is observed at δ
246.8.
Scheme 5
Oxidation Reactions
Given the electron-donating nature
of nclass="Chemical">CAAC ligaclass="Chemical">nds, it might be expected that class="Chemical">n class="Chemical">CAAC complexes should be
easier to oxidize than compounds of less electron rich NHCs. It is
surprising, therefore, that the oxidation chemistry of CAACcomplexes
does not seem to have been explored.
The oxidation of nclass="Chemical">imidazolylidene-type
class="Chemical">n class="Disease">N-heterocyclic carbene gold(I) complexes with halogens to Au(III)
products is of course well precedented and proceeds smoothly in high
yields with oxidants such as Br2 and PhICl2,
in most cases to give products of the type (NHC)AuX3 (X
= Cl, Br, I).[34−41] It was therefore surprising when initial attempts at oxidizing (AdCAAC)AuX with either PhICl2 or CsBr3 in dichloromethane at room temperature proceeded with Au–C
cleavage to give mixtures of products, even when the gold(I) precursor
was used in excess (eq 2). The reaction of (AdCAAC)AuCl with PhICl2 in CH2Cl2 gave a yellow solution from which two types of crystals could
be obtained: a small amount of colorless needles which were identified
by X-ray crystallography as the dichloroaurate(I) salt [AdCAAC-Cl][AuCl2] (20a), formed by chlorination
of the carbene ligand, and a larger component of yellow prisms which
turned out to be the product of cocrystallization of two independent
molecules of [AdCAAC-Cl][AuCl4] (20b) with one molecule of (AdCAAC)AuCl3 in the
unit cell. The 1H NMR spectrum supported an approximate
2:1 ratio of these products. Lowering the temperature to −78
°C led to recovery of the starting material. The 13C NMR resonance for the iminium carbon atom C–X is shifted
upfield in comparison to the signals for the starting carbene complexes
and observed at δ 188.5 and 186.0 for X = Cl, Br, respectively.
The menclass="CellLine">chaclass="Chemical">nism of class="Chemical">n class="Chemical">Au–C bond cleavage was not studied
in detail;
however, one plausible explanation may be that the primary oxidation
product, (AdCAAC)AuCl3, partially undergoes
photoinduced reductive elimination into Cl2 and the Au(I)complex (AdCAAC)AuCl. The eliminated chlorinecould then
react with either (AdCAAC)AuCl or (AdCAAC)AuCl3 to give the corresponding salts [AdCAAC-Cl][AuCl2] and [AdCAAC-Cl][AuCl4], respectively.
The photochemical reductive elimination of halogens from (NHC)AuBr3[39a] and from gold(III) phosphinecomplexes in the presence of olefins as halogen scavengers is known
to be facile.[42] In the present case the
carbene C–Au bond acts as such a halogen scavenger. Similar
cleavage products 21a,b are obtained using
CsBr3 under ambient light conditions (eq 2). The crystal structures of the salts 20a,b are shown in Figure 4.
Figure 4
Molecular structures
of (left) [AdCAAC-Cl]+[AuCl2]− (20a) and (right)
[AdCAAC-Cl]+[AuCl4]− (20b). Ellipsoids are shown at the 50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): 20a, Au–Cl(2) 2.2605(8),
Au–Cl(3) 2.2671(8), C(1)–Cl(1) 1.696(3), C(1)–C(2)
1.506(4), C(1)–N(1) 1.288(3), Cl(2)–Au–Cl(3)
175.91(3); 20b, Au–Cl(2) 2.2828(16), Au–Cl(3)
2.2819(17), Au–Cl(4) 2.2673(13), Au–Cl(5) 2.2813(16),
C(1)–Cl(1) 1.718(5), C(1)–C(2) 1.510(6), C(1)–N(1)
1.299(6), Cl(2)–Au–Cl(3) 89.84(7), Cl(2)–Au–Cl(4)
178.86(6).
Molecular structures
of (left) [class="Chemical">AdCAAC-Cl]+[class="Chemical">n class="Chemical">AuCl2]− (20a) and (right)
[AdCAAC-Cl]+[AuCl4]− (20b). Ellipsoids are shown at the 50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): 20a, Au–Cl(2) 2.2605(8),
Au–Cl(3) 2.2671(8), C(1)–Cl(1) 1.696(3), C(1)–C(2)
1.506(4), C(1)–N(1) 1.288(3), Cl(2)–Au–Cl(3)
175.91(3); 20b, Au–Cl(2) 2.2828(16), Au–Cl(3)
2.2819(17), Au–Cl(4) 2.2673(13), Au–Cl(5) 2.2813(16),
C(1)–Cl(1) 1.718(5), C(1)–C(2) 1.510(6), C(1)–N(1)
1.299(6), Cl(2)–Au–Cl(3) 89.84(7), Cl(2)–Au–Cl(4)
178.86(6).
However, a different
nclass="Chemical">course of this reactioclass="Chemical">n was observed wheclass="Chemical">n
the oxidatioclass="Chemical">n reactioclass="Chemical">ns were class="Chemical">n class="Chemical">conducted in the absence of ambient light. This aspect was first explored using the sterically
less hindered and synthetically more easily accessible Me2CAAC ligand and subsequently extended to AdCAAC goldcompounds.
Stirring a mixture of nclass="Chemical">[Au(Me2CAAC)2]Cl (22) aclass="Chemical">nd class="Chemical">n class="Chemical">PhICl2 in dichloromethane in the dark at
0 °C to room temperature for 6 h gave a colorless complex, [AuCl2(Me2CAAC)2]Cl (23) (Scheme 5). The molecular structure was identified by X-ray
diffraction (Figure 5). The gold atom occupies
a special position, with the Me2CAAC and Cl ligands being
related by an inversion center. The Au atom possesses the expected
square-planar geometry with a trans arrangement of the ligands. The
bond length Au–C(1) (2.064(2) Å) is slightly elongated
in comparison to those of the analogous imidazolylidenecomplexes
[AuCl2(NHC)2]+, while the Au–Cl(1)
distance is closely similar.[38b,42]
Figure 5
Solid-state structure
of the cation in [AuCl2(Me2CAAC)2]Cl (23). Ellipsoids are shown at the
50% probability level. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (deg): Au–Cl(1) 2.2681(7),
Au–C(1) 2.064(2), C(1)–C(2) 1.527(3), C(1)–N(1)
1.295(3), C(1)–Au–Cl(1) 87.37(7), C(1)–Au–C(1A)
92.63(7).
Solid-state structure
of the cation inclass="Chemical">[AuCl2(Me2CAAC)2]Cl (23). Ellipsoids are showclass="Chemical">n at the
50% probability level. class="Chemical">n class="Chemical">Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (deg): Au–Cl(1) 2.2681(7),
Au–C(1) 2.064(2), C(1)–C(2) 1.527(3), C(1)–N(1)
1.295(3), C(1)–Au–Cl(1) 87.37(7), C(1)–Au–C(1A)
92.63(7).
The crystal structure and elemental
analysis show the expected
nclass="Chemical">compositioclass="Chemical">n of the desired class="Chemical">n class="Chemical">Au(III) product, [AuCl2(Me2CAAC)2]Cl. At the same time, it is a well-known
fact that the 13C NMR resonance of the carbene carbon is
usually shifted upfield on oxidation of Au(I) carbenecomplexes to
Au(III).[38b] However, the 1H
and 13C NMR spectra in CD2Cl2 of
[AuCl2(Me2CAAC)2]Cl and its precursor
[Au(Me2CAAC)2]Cl are essentially identical:
δ(13C) 250.6. Therefore, we cannot exclude the possibility
that in solution an equilibrium exists between [AuCl2(Me2CAAC)2]Cl and its Au(I) isomer, [Au(Me2CAAC)2]Cl3, which in dichloromethane is predominantly
shifted toward the Au(I)complex. It did not prove possible, however,
to isolate the trichloride salt, and numerous attempts to pick out
different crystals led only to unit cell measurements corresponding
to the Au(III)complex [AuCl2(Me2CAAC)2]Cl.
The quality of the product strongly depends on the absence
of the
light during the reaction and on storage. For instance, the nclass="Chemical">colorless
solutioclass="Chemical">n of class="Chemical">n class="Chemical">[AuCl2(Me2CAAC)2]Cl slowly
turned yellow (within ca. 24 h) if left exposed to ambient light,
while the 1H and 13C NMR spectra of the sample
remained unchanged. The products of this reaction could not be unequivocally
determined but seemed likely to contain [AuCl4]− salts.
The oxidation of 22 with nclass="Chemical">CsBr3 as selective
class="Chemical">n class="Chemical">brominating agent took a somewhat different course. Under ambient
conditions [Au(Me2CAAC)2]Cl reacts with CsBr3 to give a mixture of orange prisms of [Au(Me2CAAC)2]Br3 (24a) and of red crystals of
[Au(Me2CAAC)2]AuBr4 (24b) (Scheme 5). In contrast, the attempted oxidation
of [Au(Me2CAAC)2]Cl with iodine gave the Au(I)
diiodochloride salt [Au(Me2CAAC)2]ClI2 (24c). Since 1H and 13C NMR spectra
are not informative, the nature of these products was confirmed by
X-ray crystallography (see the Supporting Information).
Innone of these reactions did we observe the formation
of gold(III)
nclass="Chemical">bromo or class="Chemical">n class="Chemical">iodo complexes. The reactivity of CAACcomplexes therefore
differs significantly from that of unsaturated NHCcomplexes, where
oxidation with Br2 has been shown to generate complexes
of the type (NHC)AuBr3 and [AuBr2(NHC)2]+ [35a,38b,39b] and where oxidation with iodine has given rise to compounds of the
types (NHC)AuBrI2, [AuI2(NHC)2]+, and (NHC)AuI3.[38,39a]
A similar
reactivity pattern was observed in the oxidation reactions
of the more bulky nclass="Chemical">monocarbene class="Chemical">n class="Chemical">complexes (AdCAAC)AuX (X
= Cl, Br, I). As was observed for the bis-carbene cation [Au(Me2CAAC)2]+, carbene complexes of Au(III)
are only obtained if ambient light is excluded. Thus, the reaction
of (AdCAAC)AuCl with PhICl2 over the temperature
range from 0 °C to room temperature for 6 h in the dark led to
the isolation of (AdCAAC)AuCl3 (25) as a light yellow solid in almost quantitative yield (eq 3). There was no reaction at −78 °C.
The nclass="Chemical">13C NMR spectrum of 25 shows the
class="Chemical">n class="Chemical">carbene
carbon signal at δ 218.8, substantially downfield of the 13C carbene signals of imidazolidine-type (NHC)AuCl3complexes, which are typically observed in the range of δ
130–170.[35−40] In comparison to Au(I)CAACcomplexes, which show 13Ccarbene chemical shifts of ca. δ 235–240,[6c] the Au(III)complexes are shifted upfield by
about 20 ppm. Such changes have previously been explained on the basis
of increased Lewis acidity of the Au(III) center and shielding effects
of the cis-halide ligands.[38b,39a] There was no evidence for ligand rearrangement, e.g. to [AuCl2(AdCAAC)2][AuCl4], and the
solid-state structure is retained in solution. The structure of the
complex is shown in Figure 6. The Au(III) atom
possesses square-planar geometry. The bond lengths Au–C(1)
(2.018(4) Å) and Au–Cl(2) (2.3170(13) Å in position
trans to the carbene carbon) are almost identical with those observed
in numerous (NHC)AuCl3complexes.[35−40]
Figure 6
Crystal
structure of (AdCAAC)AuCl3 (25).
Ellipsoids are shown at the 50% probability level. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au–Cl(1) 2.2972(13), Au–Cl(2) 2.3170(13),
Au–Cl(3) 2.2632(13), Au–C(1) 2.018(4), C(1)–C(2)
1.537(6), C(1)–N(1) 1.295(6), C(1)–Au–Cl(2) 174.25(13),
C(1)–Au–Cl(1) 85.64(13), C(1)–Au–Cl(2)
95.83(13), Cl(1)–Au–Cl(2) 88.79(6).
Crystal
structure of class="Chemical">(AdCAAC)AuCl3 (25).
Ellipsoids are showclass="Chemical">n at the 50% probability level. class="Chemical">n class="Chemical">Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au–Cl(1) 2.2972(13), Au–Cl(2) 2.3170(13),
Au–Cl(3) 2.2632(13), Au–C(1) 2.018(4), C(1)–C(2)
1.537(6), C(1)–N(1) 1.295(6), C(1)–Au–Cl(2) 174.25(13),
C(1)–Au–Cl(1) 85.64(13), C(1)–Au–Cl(2)
95.83(13), Cl(1)–Au–Cl(2) 88.79(6).
In nclass="Chemical">coclass="Chemical">ntrast, the reactioclass="Chemical">n of (class="Chemical">n class="Chemical">AdCAAC)AuI with
iodine
in dichloromethane under various reaction conditions (i.e., either
protected from light or unprotected, low or ambient temperature) gave
a dark red solution from which crystals of the dark red iodine adduct
(AdCAAC)AuI·I2 (26) were isolated
(eq 4). This is in contrast to the oxidative
addition of iodine observed with other types of NHCcomplexes, which
form gold(III) iodides.[38b,45] The formation of triiodides
and iodine adducts has previously been observed for phosphine and
isonitrile Au(I) complexes.[43,44] Indications for the
redox equilibrium LAuI(I3) ⇌ LAuIII(I)3 were not detected.
The structure of 26 is shown in Figure 7. Acnclass="Chemical">cordiclass="Chemical">ng to the Camclass="Chemical">n class="Chemical">bridge Structural Database
the only
closely analogous compound with a triiodide moiety is [(tBuNC)2Au][AuI2]·I2, reported
by Schmidbaur.[43] The Au–I(1) and
I(2)–I(3) bond lengths for the complex (AdCAAC)AuI·I2 (2.5684(4) and 2.7626(5) Å) are almost identical with
those for [(tBuNC)2Au][AuI2]·I2 (2.553(1) and 2.738(1) Å, respectively), but the I(1)–I(2)
distance is significantly shorter: 3.1655(5) vs 3.311(1) Å. At
the same time the I···I distance is in accordance with
typical values for polyiodidecomplexes.[46] Analysis of intermolecular contacts shows neither aurophilic interactions
(the shortest distance between gold atoms is 7.521 Å) nor polyiodidechain formation.
Figure 7
Crystal structure of (AdCAAC)AuI·I2 (26). Ellipsoids are shown at the 50% probability
level. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au–I(1) 2.5684(4), Au–C(1) 2.024(4), I(1)–I(2)
3.1655(5), I(2)–I(3) 2.7626(5), C(1)–C(2) 1.517(6),
C(1)–N(1) 1.299(6); C(1)–Au–I(1) 177.36(12),
Au–I(1)–I(2) 93.56(1), I(1)–I(2)–I(3)
177.28(2).
Crystal structure of (class="Chemical">AdCAAC)class="Chemical">n class="Chemical">AuI·I2 (26). Ellipsoids are shown at the 50% probability
level. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au–I(1) 2.5684(4), Au–C(1) 2.024(4), I(1)–I(2)
3.1655(5), I(2)–I(3) 2.7626(5), C(1)–C(2) 1.517(6),
C(1)–N(1) 1.299(6); C(1)–Au–I(1) 177.36(12),
Au–I(1)–I(2) 93.56(1), I(1)–I(2)–I(3)
177.28(2).
Conclusion
The nclass="Chemical">AdCAAC ligaclass="Chemical">nd produces a class="Chemical">n class="Chemical">gold(I) hydroxide with
slightly increased basicity in comparison to the imidazolylidene-type
complex (NHC)AuOH. It is a convenient starting material for the synthesis
of a wide range of acid/base and C–H activation reactions and
gives gold aryls even with 1,3,5-trifluorobenzene. Arylgoldcomplexes
of less acidic arenes are obtainable by the reactions of the corresponding
arylboronic acids under neutral conditions in toluene. The oxidation
reactions of CAAC-supported gold(I) complexes by halogens, on the
other hand, did not conform to the expectations for electron-rich
complexes, and only stronger oxidants, such as PhICl2,
afforded gold(III) CAACcomplexes. In bromine oxidations the CAAC
ligand proved to be a halide scavenger, while iodine formed a gold(I)
triiodide. The halidecomplexes readily decompose under the influence
of light, and exclusion of light is required if cleavage of the Au–carbene
bond by halogens is to be avoided. With such precautions, the first
examples of gold(III) CAACcomplexes could be prepared in almost quantitative
yields. The reaction patterns of CAAC-type carbenes provide therefore
an interesting contrast to those of more strongly π-accepting[13i] imidazole-based NHC carbenes.
Experimental Section
General Considerations
Unless stated
otherwise, all
reactions were carried out in air. Solvents were distilled and dried
as required. nclass="Chemical">Pentafluorobenzene, class="Chemical">n class="Chemical">1,2,4,5-tetrafluorobenzene, 1,3,5-trifluorobenzene,
sodium tert-butoxide, diethyl malonate, trimethylsilyl
cyanide, triethoxysilane, triflimide, tert-butyl
alcohol, BuNC, KCN, and norbornene were
purchased from Sigma-Aldrich and used as received. (AdCAAC)AuCl[6c] and Me2CAAC[47] were obtained according to a literature procedure. 1H, 13C{1H}, and 19F NMR spectra were recorded
using a Bruker Avance DPX-300 MHz NMR spectrometer. 1H
NMR spectra (300.13 MHz) and 13C{1H} (75.47
MHz) were referenced to CD2Cl2 at δ 5.32
(13C, δ 54.0), C6D6 at δ
7.16 (13C, δ 128.4), CDCl3 at δ
7.26 (δ 13C 77.2), or C6D5Br
at δ 7.30 for the most downfield signal (13C, δ
122.5 for the most upfield signal) ppm. 19F NMR spectra
(282.4 MHz) were referenced externally to CFCl3 and internally
to C6F6 (δF −164.9).
IR spectra were recorded using a PerkinElmer Spectrum One FT-IR spectrometer
equipped with a diamond ATR attachment. Elemental analyses were performed
by the London Metropolitan University.
Synthesis of (AdCAAC)AuOBu (2)
An oven-dried 25 mL Schlenk flask was
equipped with a stirring bar and nclass="CellLine">charged with class="Chemical">n class="Chemical">(AdCAAC)AuCl
(303 mg, 0.5 mmol) and sodium tert-butoxide (48 mg,
0.5 mmol) under an argon atmosphere. Anhydrous toluene (15 mL) was
added, and the resulting white suspension was stirred in the dark
for 5 h and filtered through a Celite pad (2 cm), which was washed
with an additional 10 mL of toluene. The volatiles were evaporated
under vacuum, affording a white solid: yield 307 mg (0.475 mmol, 95.5%). 1H NMR (300 MHz, CD2Cl2): δ 7.43
(t, J = 7.6 Hz, 1H, CH-aromatic), 7.27 (d, J = 7.6 Hz, 2H, CH-aromatic), 4.12 (br d, J = 13.2 Hz, 2H, CH2), 2.77 (sept, J = 6.6 Hz, 2H, CH(CH3)2), 2.32–1.75 (m, 14H, adamantyl CH and CH2), 1.44 (d, J = 6.6 Hz, 6H, CH(CH3)2), 1.31 (s, 6H, 2CH3), 1.28 (d, J = 6.6 Hz, 6H, CH(CH3)2), 0.91 (s, 9H, OC(CH3)3) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 238.1 (C carbene), 144.9 (o-C),
136.4 (Ar, C), 129.0 (Ar, p-C), 124.8 (Ar, m-C), 75.9 (Cq), 70.2 (Cq, OC(CH)3), 63.7
(Cq), 48.7 (CH2), 39.0 (CH2), 36.8,
34.9 (OC(CH3)3), 34.8, 34.4
(CH2), 29.0 (CH), 28.9, 27.7, 27.3, 26.5, 22.9 (CH3) ppm. IR (ATR, cm–1): 2900, 2846, 1493,
1447, 1343, 1188, 958, 802, 765, 587. Anal. Calcd for C31H48AuNO (647.68): C, 57.49; H, 7.47; N, 2.16. Found: C,
57.58; H, 7.50; N, 2.18.
Synthesis of (AdCAAC)AuOH (3)
Method A
A 50 mL Schlenk flask was nclass="CellLine">charged with class="Chemical">n class="Chemical">(AdCAAC)AuCl (303 mg, 0.5 mmol), freshly ground KOH (285 mg,
5 mmol), and 10 mL of THF. To the stirred suspension was added tert-butyl alcohol (0.02 mL, 0.2 mmol), and stirring was
continued for 36 h at room temperature. The dark suspension was filtered
through a Celite pad (3 cm) and washed with additional THF (2 ×
5 mL). Water (4 mL) was added to the THF solution, after which it
was concentrated to ca. 7 mL. Water (10 mL) was added to the cloudy
suspension. All volatiles were removed under vacuum (30 °C, 20
mbar). If any coloration of the solid remained, it could be redissolved
in THF/H2O (4:1) and passed through Celite. The white residue
was washed with hexanes (2 × 5 mL) and dried under vacuum for
1 day. Yield: 282 mg (0.48 mmol, 96%).
Method B
An excess
of distilled class="Chemical">water (5 mL) was added
to the stirred solutioclass="Chemical">n of (class="Chemical">n class="Chemical">AdCAAC)AuOBu (194 mg, 0.30 mmol) in 1 mL of THF. The milky suspension
was stirred for 15 min, and the volatiles were removed under vacuum.
The white residue was washed with hexanes (5 mL) and dried under vacuum
for 1 day. Yield: 171 mg (0.29 mmol, 97%).
class="Chemical">1H NMR
(300 MHz, class="Chemical">n class="Chemical">C6D5Br): δ 7.21 (t, J = 7.9 Hz, 1H, CH-aromatic), 7.06 (d, J = 7.9 Hz, 2H, CH-aromatic), 4.21(br d, J = 13.2
Hz, 2H, CH2), 2.69 (sept, J = 6.6 Hz, 2H, CH(CH3)2),
1.98–1.52 (m, 14H, adamantyl CH and CH2), 1.46 (d, J = 6.6 Hz, 6H, CH(CH3)2), 1.16 (d, J = 6.6 Hz, 6H, CH(CH3)2), 0.99 (s, 6H, 2CH3), −0.29
(br s, 1H, OH) ppm. 13C{1H} NMR (75 MHz, C6D5Br): δ 238.2 (C carbene), 145.1 (o-C),
136.0 (Cipso), expected signal at ca. 129.0 (p-C) overlaps with solvent peak of C6D5Br, 125.1
(m-C), 75.8 (Cq), 63.8 (Cq),
48.6 (CH2), 39.3 (CH2), 37.1, 35.3, 34.7 (CH2), 29.2(CH), 29.0, 28.0, 27.6, 27.0, 23.3
(CH3) ppm. IR (ATR, cm–1): 3671, 3605 (br), 2960, 2900, 1500, 1448, 1358, 1098, 945, 803,
778, 540. Anal. Calcd for C27H40AuNO (591.57):
C, 54.82; H, 6.81; N, 2.37. Found: C, 54.71; H, 6.84; N, 2.41.
Synthesis of (AdCAAC)Au(p-C6H4F)] (4)
Under
annclass="Chemical">argon atmosphere, aclass="Chemical">n oveclass="Chemical">n-dried 25
mL Schleclass="Chemical">nk flask was class="Chemical">n class="CellLine">charged with a stirring bar, (AdCAAC)AuOtBu (97 mg, 0.15 mmol), and p-fluorophenylboronic
acid (22 mg, 0.15 mmol). Anhydrous toluene (5 mL) was added, and the
resulting suspension was stirred overnight. The reaction mixture was
filtered through a Celite pad (2 cm), which was washed with another
8 mL of toluene. The volatiles were removed under vacuum to give an
off-white product, which was washed with hexanes (2 × 4 mL) and
dried under vacuum. Yield: 92 mg (0.14 mmol, 92%).
A scintillation vial was nclass="CellLine">charged iclass="Chemical">n air with
a stirriclass="Chemical">ng bar, (class="Chemical">n class="Chemical">AdCAAC)AuOH (60 mg, 0.10 mmol) and p-fluorophenylboronic acid (15 mg, 0.10 mmol). Toluene (4
mL) was added and the resulting suspension was stirred overnight.
The mixture was filtered through a Celite pad (2 cm) which was washed
with another 8 mL of toluene. All volatiles were removed under vacuum
to give an off white product which was washed with hexanes (2 ×
4 mL) and dried under vacuum. Yield: 65.5 mg (0.097 mmol, 97%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ
7.45 (t, J = 7.6 Hz, 1H, CH-aromatic), 7.29 (d, J = 7.6 Hz, 2H, CH-aromatic), 6.99 and 6.72 (dd, 4H, JAB = ca. 9.7 Hz, 3JHa-F = ca. 7.9 Hz, 4JHb-F = ca. 5.1 Hz, p-C6H4), 4.21(br d, J = 12.6 Hz, 2H, CH2), 2.86 (sept, J = 6.7 Hz,
2H, CH(CH3)2), 2.31–1.81
(m, 14H, adamantly CH and CH2), 1.45 (d, J = 6.7 Hz, 6H, CH(CH3)2),
1.35 (s, 6H, 2CH3), 1.31 (d, J = 6.7 Hz,
6H, CH(CH3)2).[19]F NMR (282 MHz, CD2Cl2): δ −119.9. 13C{1H} NMR (75 MHz, CD2Cl2): δ 263.9 (C carbene), 163.4 (d, 4JC–F = 3.9 Hz, Au-Cq, p-C6H4F), 160.9 (d, 1JC–F= 239 Hz, CF, p-C6H4F), 145.2 (Ar, o-C), 141.2 (d, 3JC–F= 5.5 Hz, CH, p-C6H4F), 135.6 (Cipso), 129.0 (p-C), 124.6 (m-C), 112.8 (d, 2JC–F= 17.1 Hz, CH, p-C6H4F), 77.1
(Cq), 65.2 (Cq), 48.8 (CH2), 39.0
(CH2), 37.1, 35.3, 34.4 (CH2), 29.0 (CH), 28.99 (almost overlapping with signal at 29.0), 28.2,
27.4, 26.1, 22.8 (CH3) ppm. Anal. Calcd
for C28H39AuN2 (669.66): C, 59.19;
H, 6.47; N, 2.09. Found: C, 59.01; H, 6.46; N, 2.13.
Synthesis
of (AdCAAC)Au(OAcF)] (5)
A Schlenk flask was class="CellLine">charged with (class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg,
0.10 mmol) and a trifluoroacetic acid solution
(9 μL, 0.11 mmol) in toluene (1 mL). The resulting solution
was stirred for 4 h. All volatiles were removed under vacuum. The
residue was washed with hexanes (2 × 2 mL) and dried under vacuum
to give a white solid. Yield: 66.5 mg (0.096 mmol, 96%).
A Schlenk flask was class="CellLine">charged with class="Chemical">n class="Chemical">(AdCAAC)AuCl (59 mg,
0.1 mmol), silver trifluoroacetate (23 mg, 0.10
mmol), and CH2Cl2 (2 mL). The resulting suspension
was stirred for 30 min in the dark. The mixture was filtered through
a Celite pad (2 cm), which was washed with another 8 mL of CH2Cl2. All volatiles were removed under vacuum to
leave an off-white product, which was dried under vacuum. Yield: 63.5
mg (0.092 mmol, 92%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.49 (t, J = 7.7 Hz, 1H,
CH-aromatic), 7.30 (d, J = 7.7 Hz, 2H, CH-aromatic),
4.00 (br d, J = 12.6 Hz, 2H, CH2), 2.74 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.39–1.81 (m, 14H, adamantyl
CH and CH2), 1.38 (d, J = 6.7 Hz, 6H,
CH(CH3)2), 1.35 (s, 6H, 2CH3),1.31 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 19F NMR (282 MHz, CD2Cl2): δ −74.5 ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 232.4
(C carbene), 160.7 (quart. 2JC–F= 37.8 Hz, CO2), 144.8
(o-C), 135.4 (Cipso), 129.8 (p-C), 125.0 (m-C), 117.7 (quart. 1JC–F= 293 Hz, CF3), 77.2 (Cq), 63.6 (Cq), 48.2 (CH2), 38.9 (CH2), 37.0, 35.1, 34.4
(CH2), 29.0 (CH), 28.9, 27.7, 27.2, 26.3,
22.6 (CH3) ppm. IR (ATR, cm–1): 2968, 2908, 1701, 1527, 1450, 1407, 1372, 1187, 1135, 1097, 841,
804, 727, 609, 520. Anal. Calcd for C29H39AuF3NO2 (687.58): C, 50.66; H, 5.72; N, 2.04. Found:
C, 50.72; H, 5.80; N, 2.02.
Synthesis of (AdCAAC)Au(3,5-di-tert-butylphenolate) (6)
A scintillation vial was
nclass="CellLine">charged with a stirriclass="Chemical">ng bar, (class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg, 0.10
mmol), and 3,5-di-tert-butylphenol (21 mg, 0.102
mmol). Toluene (3 mL) was added and the resulting yellow solution
was stirred overnight. All volatiles were evaporated under vacuum,
affording the product as a white solid, which was washed with hexanes
(2 × 4 mL) and dried under vacuum. Yield: 75.5 mg (0.097 mmol,
97%).
class="Chemical">1H NMR (300 MHz, C6D6): δ 7.18 (t, J = 7.7 Hz, class="Chemical">n class="Chemical">1H, CH-aromatic),
7.01 (d, J = 7.7 Hz, 2H, CH-aromatic), 6.98 (br d, J = 1.7 Hz, 2H, CH, phenolate), 6.93 (br
t, J = 1.7 Hz, 1H, CH, phenolate),
4.40 (br d, J = 12.2 Hz, 2H, CH2), 2.67 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.15–1.60 (m, 14H, adamantyl
CH and CH2), 1.51 (d, J = 6.7 Hz, 6H,
CH(CH3)2), 1.40 (s, 18H, two Bu groups), 1.09 (d, J =
6.7 Hz, 6H, CH(CH3)2), 0.79
(s, 6H, 2CH3) ppm. 13C{1H} NMR (75
MHz, C6D6): δ 236.1 (C carbene), 168.6
(O-C phenolate), 150.4 (Cmeta phenolate),
144.8 (Co aromatic), 135.3 (Cipso aromatic),
129.9 (CHp aromatic), 113.9 (CHo phenolate),
108.7 (CHpara phenolate), 75.5 (Cq), 63.5 (Cq), 48.0 (CH2), 38.9 (CH2), 36.9, 35.1,
34.7 (C(CH3)3), 34.4 (CH2), 31.9 (C(CH3)3),
29.1(CH), 28.3, 27.6, 27.3, 26.7, 22.6 (CH3) ppm. IR (ATR, cm–1): 2962, 2897,
1576, 1509, 1463, 1422, 1320, 1098, 973, 804, 705, 643, 582, 474.
Anal. Calcd for C41H60AuNO (779.88): C, 63.14;
H, 7.75; N, 1.80. Found: C, 63.23; H, 7.81; N, 1.85.
Synthesis of
(AdCAAC)Au(NTf2) (7)
A
Schlenk flask was nclass="CellLine">charged with a stirriclass="Chemical">ng bar, (class="Chemical">n class="Chemical">AdCAAC)AuOH
(59 mg, 0.10 mmol), and HNTf2 (30 mg,
0.105 mmol) under argon. Toluene (1 mL) was added, and the resulting
suspension was stirred overnight. The product was precipitated with
hexanes (10 mL) and dried under vacuum. The residue was washed with
hexanes (2 × 2 mL) and dried under vacuum. The microcrystalline
product contains half a molecule of toluene, while precipitation from
dichloromethane with hexanes gives the CH2Cl2 solvate: yield 86 mg (0.091 mmol, 91%).
class="Chemical">1H NMR
(300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.45 (t, J = 7.8 Hz, 1H, CH-aromatic), 7.28 (d, J = 7.8 Hz, 2H, CH-aromatic), 3.82 (br d, J = 13.2
Hz, 2H, CH2), 2.71 (sept, J = 6.7 Hz, 2H, CH(CH3)2),
2.40–1.81 (m, 14H, adamantyl CH and CH2), 1.39 (s,
6H, 2CH3),1.36 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.30 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 19F NMR (282 MHz, CD2Cl2): δ −75.3
ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 233.8 (C carbene), 144.5 (o-C),
135.5 (Cipso), 129.8 (p-C), 125.2 (m-C), 119.1 (quart. 1JC–F= 323.3 Hz, CF3), 77.8
(Cq), 63.8 (Cq), 48.3 (CH2), 38.8
(CH2), 37.0, 34.7, 34.4 (CH2), 29.2 (CH), 29.0, 27.5, 27.1, 26.0, 23.0 (CH3) ppm. IR (ATR, cm–1): 2907, 2852, 1532,
1450, 1397, 1375, 1192, 1131, 1053, 955, 830, 654, 607, 567, 507.
Anal. Calcd for C29H39AuF6N2O4S2·CH2Cl2 (939.64):
C, 38.35; H, 4.40; N, 2.98. Found: C, 38.05; H, 4.23; N, 3.18.
Synthesis
of (AdCAAC)Au(CH(CO2Et)2) (8)
A scintillation vial was nclass="CellLine">charged
with a stirriclass="Chemical">ng bar, (class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg, 0.10 mmol), and
diethyl malonate (16 mg, 0.1 mmol). Toluene (2 mL) was added, and
the resulting suspension was stirred overnight. All volatiles were
evaporated under vacuum, affording the product as a white solid, which
was washed with hexanes (2 × 2 mL) and dried under vacuum. Yield:
72 mg (0.098 mmol, 98%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CDCl3): δ 7.38 (t, J = 7.7 Hz, 1H, CH-aromatic),
7.21 (d, J = 7.7 Hz, 2H, CH-aromatic), 3.91 (br d, J = 12.4 Hz, 2H, CH2) overlapping
with 3.88 (q, J = 7.3 Hz, 2H, OCHCH3),3.76 (q, J = 7.3 Hz, 2H, OCHCH3), 3.41
(s, 1H, CH(CO2Et)2), 2.69 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.27–1.74 (m, 14H, adamantyl CH and CH2), 1.37 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.31 (s, 6H, 2CH3), 1.26 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.05 (t, J = 7.3 Hz, 6H, OCH2CH) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ 253.2 (C carbene), 172.7 (C=O malonate),
145.0 (o-C), 135.2 (Cipso), 129.3 (p-C), 124.7 (m-C), 77.1 (Cq,
overlapping with signal from CDCl3), 64.4 (Cq), 58.4 (OCH2-malonate) 48.6 (CH2), 42.3 (CH-malonate),
39.0 (CH2), 37.0, 35.2, 34.5 (CH2), 29.2 (CH), 29.0, 27.8, 27.1, 26.6, 23.1 (CH3), 14.5 (CH3-malonate) ppm. Anal.
Calcd for C34H50AuNO4 (733.73): C,
55.66; H, 6.87; N, 1.91. Found: C, 55.54; H, 6.95; N, 1.94.
Synthesis
of (AdCAAC)AuC≡CPh (9)
A scintillation
vial was nclass="CellLine">charged with a stirriclass="Chemical">ng bar,
(class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg, 0.10 mmol), and phenylacetylene (17
mg, 0.166 mmol). Toluene (2 mL) was added, and the resulting suspension
was stirred overnight. All volatiles were evaporated under vacuum,
affording the product as a white solid, which was washed with hexanes
(2 × 2 mL) and dried under vacuum. Yield: 64 mg (0.095 mmol,
95%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CDCl3): δ
7.40 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.33 (br d, J = 7.6 Hz, 2H, CH, phenylacetylide), 7.24
(d, J = 7.7 Hz, 2H, CH-aromatic), 7.12 (br t, J = 7.6 Hz, 2H, CH, phenylacetylide),7.05
(br tt, 3J = 7.6 Hz,4J = 1.4 Hz, 1H, CH, phenylacetylide), 4.02
(br d, J = 12.4 Hz, 2H, CH2), 2.77 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.28–1.78 (m, 14H, adamantyl
CH and CH2), 1.47 (d, J = 6.7 Hz, 6H,
CH(CH3)2), 1.31 (s, 6H, 2CH3), 1.29 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR
(75 MHz, CD2Cl2): δ 257.5 (C carbene),
144.9 (o-C), 134.8 (Cipso aromatic), 132.3
(Ph acetylide), 129.4 (p-C), 127.5 (Ph acetylide),
127.0 (C acetylide), 126.2 (C aromatic acetylide), 125.7 (Ph acetylide),
124.8 (m-C), 106.8 (C acetylide), 77.1 (Cq), 65.2 (Cq), 48.7 (CH2), 39.0 (CH2), 37.0, 35.6, 34.5 (CH2), 29.1(CH),
29.0, 27.6, 27.2, 27.0, 23.0 (CH3) ppm.
IR (ATR, cm–1): 2968, 2892, 2115 (C≡C), 1508,
1447, 1368, 1098, 910, 805, 754, 693, 527. Anal. Calcd for C35H44AuN (675.69): C, 62.21; H, 6.56; N, 2.07. Found: C,
62.13; H, 6.62; N, 2.18.
Synthesis of (AdCAAC)Au(C6F5) (10)
A Schlenk flask
was nclass="CellLine">charged with (class="Chemical">n class="Chemical">AdCAAC)AuOH (118 mg, 0.2 mmol) and a
pentafluorobenzene solution
(42 μL, 0.4 mmol) in toluene (2 mL). The resulting mixture was
heated to 60 °C for 18 h. The slightly pink solution was filtered
through a Celite pad (1 cm) which was washed with an additional 6
mL of toluene. The solution was concentrated to ca. 0.3 mL under vacuum
and the white residue precipitated with hexanes (10 mL). The resulting
suspension was centrifuged. The solid was washed with hexanes (2 ×
4 mL) and dried under vacuum to give an off-white solid. Yield: 140
mg (0.19 mmol, 95%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CDCl3): δ 7.44 (t, J = 7.8 Hz, 1H, CH-aromatic),
7.25 (d, J = 7.8 Hz, 2H, CH-aromatic), 4.09 (br d, J = 13.2 Hz, 2H, CH2), 2.79
(sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.33–1.81 (m, 14H, adamantyl CH and
CH2), 1.38 (s, 6H, 2CH3), 1.36 (d, J = 6.7 Hz, 6H, CH(CH3)2),
1.29 (d, J = 6.7 Hz, 6H, CH(CH3)2)ppm. 19F NMR (282 MHz, CDCl3): δ −115.3 to −115.5 (m, 2F), −160.5
(t, J = 20.7 Hz, 1F), −163.43 to −163.70
(m, 2F) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ (Au–C from C6F5 was not observed) 258.5 (C carbene), 150.5–147.3 (d
m,1JC–F = 226 Hz, CF), 144.9 (Co aromatic), 139.6–136.5
(d m, 1JC–F = 239 Hz, CF), 138.2–134.9 (d m, 1JC–F = 252 Hz, CF), 135.2 (Cipso), 129.4 (p-C), 124.8 (m-C), 77.2 (Cq), 64.9 (Cq), 48.9 (CH2), 39.0 (CH2), 37.2, 35.2, 34.5 (CH2), 29.3
(CH), 29.0, 27.8, 27.2, 26.3, 23.2 (CH3) ppm. Anal. Calcd for C33H39AuF5N (741.62): C, 53.44; H, 5.30; N, 1.89. Found: C, 53.59; H,
5.39; N, 1.93.
Synthesis of (AdCAAC)Au(p-C6HF4) (11)
The nclass="Chemical">compouclass="Chemical">nd was
made iclass="Chemical">n a fashioclass="Chemical">n similar to that for 10 from (class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg, 0.10 mmol), and 1,2,4,5-tetrafluorobenzene (22
μL, 0.20 mmol) solution in toluene (2 mL). The resulting solution
was heated to 80 °C for 18 h. The slightly pink solution was
filtered through Celite pad (1 cm) which was washed with an additional
with 6 mL of toluene. Concentration and precipitation with hexanes
gave an off-white solid. Yield: 67 mg (0.093 mmol, 93%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.46
(t, J = 7.6 Hz, 1H, CH-aromatic), 7.29 (d, J = 7.6 Hz, 2H, CH-aromatic), 6.55 (tt, J = 9.5 and 6.9 Hz, 1H), 4.09
(br d, J = 12.9 Hz, 2H, CH2), 2.83 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.35–1.83 (m, 14H, adamantyl
CH and CH2), 1.38 (d, J = 6.7 Hz, 6H,
CH(CH3)2), 1.38 (s, 6H, 2CH3),1.31 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 19F NMR (282 MHz, CD2Cl2): δ −117.4 to −117.6 (m,
2F), −141.9 to −142.1 (m, 2F) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 258.4
(C carbene), 151.0–146.7 (d m, 1JC–F= 228 Hz, CF), 145.1 (o-C), 147.1–143.4 (d m, 1JC–F= 250 Hz, CF), 140.4 (t m, 2JC–F= 59 Hz, C tetrafluoroaryl), 135.4
(Cipso), 129.2 (p-C), 124.7 (m-C), 102.0 (t, 2JC–F = 23.7 Hz, CH tetrafluoroaryl), 77.5 (Cq), 65.0 (Cq), 48.7 (CH2), 39.0 (CH2), 37.2, 35.2, 34.4 (CH2), 29.1 (CH),
29.0, 28.1, 27.4, 26.0, 22.9 (CH3) ppm.
Anal. Calcd for C33H40AuF4N (723.63):
C, 54.77; H, 5.57; N, 1.94. Found: C, 55.17; H, 5.78; N, 2.09.
Reaction
of (AdCAAC)Au(OH) with 1,3,5-Trifluorobenzene
A J. Young NMR tube was loaded with (nclass="Chemical">AdCAAC)class="Chemical">n class="Chemical">AuOH (30
mg, 0.05 mmol) and 1,3,5-trifluorobenzene (15 μL, 0.152 mmol)
solution in toluene-d8 (0.4 mL) and sealed.
The resulting solution was heated to 90 °C for 18 h. The first
signals for the product appear after 2 h of heating. The yellow solution
with some black precipitate was cooled to room temperature. The major
product crystallizing from the solution after 8 h was the O-bridged
cluster [(AdCAAC)3Au3(μ-O)]OH (identified
by X-ray crystallography as the C6H3F3 solvate) (11 mg). The yellow solution was decanted and filtered
through a pipet filled with Celite (1 cm), which was washed with an
additional 4 mL of toluene. Concentration and precipitation with hexanes
gave a yellow solid (11 mg) as a mixture of products. Attempts to
increase the reaction time to 48 h led to significant formation of
decomposition products. 19F NMR (282 MHz, CD2Cl2): δ −84.60 (m, 2F), −116.81 to
−116.92 (m, 1F) ppm.
Synthesis of (AdCAAC)Au(2,4,6-C6H2F3) (12)
A Schlenk
flask
was loaded with nclass="Chemical">(AdCAAC)AuCl (60 mg, 0.1 mmol), class="Chemical">n class="Chemical">1,3,5-trifluorobenzene
(60 μL, 0.608 mmol), NaOtBu (29 mg, 0.3 mmol), and
1,4-dioxane (0.8 mL) and sealed. The resulting suspension was heated
to 75 °C for 18 h. After the suspension was cooled to room temperature,
the solid was extracted with CH2Cl2 and the
extract filtered through a pad of Celite (1 cm). The solution was
concentrated, the product precipitated with hexanes, and the solvent
decanted. All volatiles were evaporated to give an off-white solid.
An analytically pure sample was obtained after flash chromatography
(CH2Cl2/hexane 30/70). Evaporation of all volatiles
gave a white solid: yield 34 mg (0.049 mmol, 49%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.44 (t, J = 7.6 Hz, 1H, CH-aromatic), 7.27 (d, J = 7.6 Hz, 2H, CH-aromatic), 6.40–6.34 (m, 2H, C6H2F3), 4.13 (br d, J = 12.0
Hz, 2H, CH2), 2.82 (sept, J = 6.7 Hz, 2H, CH(CH3)2),
2.33–1.81 (m, 14H, adamantyl CH and CH2), 1.37 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.35 (s, 6H, 2CH3), 1.29 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 19F NMR (282 MHz, CD2Cl2): δ −84.60
(m, 2F), −116.81 to −116.92 (m, 1F) ppm. 13C NMR (75 MHz, CD2Cl2): δ (C-F from C6H2F3 was not observed)
259.7 (C carbene), 170.6–169.9 (m, Au-Cq, trifluoroaryl),
145.1 (o-C), 135.4 (Cipso), 129.1 (p-C), 124.6 (m-C), 97.6 (ddd, JC–F = 36.5, 23.3, 4.8 Hz, CH trifluoroaryl),
77.3 (Cq), 65.0 (Cq), 48.7 (CH2),
39.1 (CH2), 37.2, 35.1, 34.3 (CH2), 29.05 (CH), 29.0, 28.1, 27.4, 26.0, 22.6 (CH3) ppm. Anal. Calcd for C33H41AuF3N (705.64): C, 56.17; H, 5.86; N, 1.98. Found: C, 56.39; H,
5.98; N, 1.87.
Synthesis of (AdCAAC)Au(CH2C(O)-p-methoxyphenyl) (13)
A scintillation
vial was nclass="CellLine">charged with (class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg, 0.10 mmol) and p-methoxyacetophenone (20 mg, 0.13 mmol) in toluene (2 mL).
The resulting mixture was heated to 70 °C for 12 h. The slightly
yellow solution was filtered through a Celite pad (1 cm) which was
washed with an additional 6 mL of toluene. The solution was concentrated
to ca. 0.3 mL under vacuum and the white residue precipitated with
hexanes (10 mL). The resulting suspension was centrifuged. The solid
was washed with hexanes (2 × 4 mL) and dried under vacuum to
give an off-white solid. Yield: 60 mg (0.083 mmol, 83%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 8.21
(d, 2H, AA′BB′, JAB = ca.
8.2 Hz, p-C6H4), 7.13 (t, J = 7.6 Hz, 1H, CH-aromatic), 6.95 (d, J = 7.6 Hz, 2H, CH-aromatic), 6.76 (d, 2H, AA′BB′, JAB = ca. 8.2 Hz, p-C6H4), 4.17 (br d, J = 12.9 Hz, 2H, CH2), 3.31 (s, 3H, OCH), 3.25 (s, 2H, CHAu), 2.63 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 1.97–1.54 (m, 14H, adamantyl CH and CH2), 1.48 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.08 (d, J = 6.7 Hz,
6H, CH(CH3)2), 0.79 (s, 6H,
2CH3) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 260.2 (C carbene), 200.9 (C=O),
161.1 (MeOCipso methoxyphenyl), 144.7
(o-C), 135.3 (Cipso), 134.1 (Cipso methoxyphenyl), 129.9 (m-C methoxyphenyl),
129.4 (p-C), 124.7 (m-C), 112.6
(o-C methoxyphenyl), 76.3 (Cq), 64.5 (Cq), 54.5 (CH3O methoxyphenyl),
48.3 (CH2), 38.9 (CH2), 37.0, 35.0, 34.3 (CH2), 33.8 (CH2Au), 29.0 (CH), 28.4, 27.8, 27.3, 26.3, 22.9 (CH3) ppm. IR (ATR, cm–1): 2968, 2904, 1625
(C=O), 1598, 1507, 1464, 1369, 1306, 1245, 1163, 1097, 1023,
840, 805, 589. Anal. Calcd for C36H49AuNO2 (724.74): C, 59.66; H, 6.81; N, 1.93. Found: C, 59.75; H,
6.92; N, 1.95.
Synthesis of (AdCAAC)Au(deoxybenzoinyl)
(14)
A scintillation vial was nclass="CellLine">charged with (class="Chemical">n class="Chemical">AdCAAC)AuOH
(76 mg, 0.128 mmol) and deoxybenzoin (28 mg, 0.142 mmol) in toluene
(2 mL). The resulting mixture was heated to 70 °C for 12 h. All
volatiles were removed from the gray suspension. The product was extracted
with CH2Cl2 and passed through a Celite pad
(1 cm) which was washed with an additional 6 mL of CH2Cl2. The solution was concentrated to ca. 0.3 mL under vacuum
and the white residue precipitated with hexanes (10 mL). The resulting
suspension was centrifuged. The residue was washed with hexanes (2
× 4 mL) and dried under vacuum to give a white solid. Yield:
87 mg (0.116 mmol, 92%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.73–7.70 (m, 2H, C6H5), 7.41 (t, J = 7.6 Hz, 1H, CH-aromatic),
7.31 (tt, J = 7.6 and 1.8 Hz, 1H, C6H5), 7.24 (d, J = 7.6 Hz, 2H, CH-aromatic)
overlapping with 7.22–7.20 (m, 1H, C6H5), 7.12–7.70 (m, 5H, C6H5), 6.84 (tt, J = 7.6 and 1.8 Hz, 1H, C6H5), 4.80
(s, 1H, Au-CH), diastereotopic signals for carbene ligand 3.75 (br
d, J = 12.9 Hz, 1H, CH2), 3.43 (br d, J = 12.9 Hz, 1H, CH2), 2.64 (sept, J = 6.7 Hz, 1H, CH(CH3)2), 2.57 (sept, J = 6.7 Hz, 1H, CH(CH3)2),
2.22–1.55 (m, 14H, adamantyl CH and CH2), 1.29 (d, J = 6.7 Hz, 3H, CH(CH3)2), 1.26 (s, 3H, C-CH3), 1.25 (d, J = 6.7 Hz, 3H, CH(CH3)2) overlapping
with 1.25 (s, 3H, C–CH3), 1.16 (d, J = 6.7 Hz, 3H, CH(CH3)2),
0.89 (d, J = 6.7 Hz, 3H, CH(CH3)2) ppm. 13C{1H} NMR (75
MHz, CD2Cl2): δ 254.6 (C carbene), 194.9
(C=O), 144.7 (o-Co aromatic), 144.6,
144.5, 141.2, 135.6 (Cipso), 129.4 (p-C),
129.3, 128.2, 127.5, 126.9, 126.9, 124.9 (m-C),124.8,
121.2, 77.0 (Cq), 64.2 (Cq), 56.3 (CH-Au), 48.6 (CH2), 38.9 (CH2), 37.0, 36.8,
34.9, 34.6, 34.3 (CH2), 34.2 (CH2), 29.0 (CH), 28.9, 28.8, 27.7, 27.2, 26.0, 25.4, 22.9 and 22.7(CH3) ppm. IR (ATR, cm–1): 2968,
2900, 1614 (CO), 1574, 1519, 1449, 1368, 1282, 1195, 1097, 1039, 931,
847, 807, 695, 579. Anal. Calcd for C39H50AuNO
(745.78): C, 62.81; H, 6.76; N, 1.88. Found: C, 62.95; H, 6.86; N,
1.93.
Synthesis of (AdCAAC)Au(CH2SO2Ph) (15)
A scintillation vial was nclass="CellLine">charged with
(class="Chemical">n class="Chemical">AdCAAC)AuOH (94 mg, 0.16 mmol) and methyl phenyl sulfone
(30 mg, 0.19 mmol) in toluene (2 mL). The resulting mixture was heated
to 70 °C overnight. The slightly yellow solution was filtered
through a Celite pad (1 cm) which was washed with an additional 6
mL of toluene. The solution was concentrated to ca. 0.3 mL under vacuum
and the white residue precipitated with hexanes (10 mL). The resulting
suspension was centrifuged. The solid was washed with hexanes (2 ×
4 mL) and dried under vacuum to give an off-white solid. Yield: 98
mg (0.134 mmol, 85%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.77–7.74 (m, 2H, sulfone C6H5), 7.43 (t, J = 7.8 Hz, 1H, CH-aromatic)
overlapping with 7.42–7.36 (m, 3H, sulfone C6H5), 7.26 (d, J = 7.8 Hz, 2H, CH-aromatic),
4.05 (br d, J = 12.0 Hz, 2H, CH2), 2.79 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.55 (s, 2H, CHAu), 2.34–1.80
(m, 14H, adamantyl CH and CH2), 1.37 (d, J = 6.7 Hz, 6H, CH(CH3)2),
1.32 (s, 6H, 2CH3), 1.29 (d, J = 6.7 Hz,
6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ
258.2 (C carbene), 147.5 (Cipso sulfone Ph), 145.1 (o-C), 135.3 (Cipso), 130.7 (p-C sulfone), 129.2 (p-C), 128.3 (m-C sulfone), 125.9 (o-C sulfone), 124.6 (m-C), 77.3 (Cq), 65.1 (Cq), 49.7 (CH2Au, sulfone), 48.6 (CH2), 39.0 (CH2),
37.1, 35.2, 34.4 (CH2), 29.0 (CH), 28.9, 27.9, 27.4, 26.3,
22.7 (CH3) ppm. Anal. Calcd for C34H46AuNSO2 (729.76): C, 55.96; H, 6.35; N, 1.92. Found: C,
56.13; H, 6.47; N, 1.99.
Synthesis of [(AdCAAC)Au(CO)]SbF6 (16)
A Schlenk flask was nclass="CellLine">charged with
class="Chemical">n class="Chemical">(AdCAAC)AuCl (60.5 mg, 0.1 mmol), AgSbF6 (35
mg, 0.1 mmol),
and CH2Cl2 (2 mL). The resulting suspension
was stirred for 1 h in the dark. The mixture was filtered through
a Celite pad (2 cm), which was washed with another 8 mL of CH2Cl2. The colorless solution was concentrated to
ca. 3 mL, cooled to −20 °C, and saturated by bubbling
with CO for 1 min followed by stirring at room temperature for 2 h.
Precipitating with an excess of hexanes (15 mL), decanting the solvents,
and removing volatiles under vacuum for 0.5 min afforded the product
as a white solid. Yield: 80.0 mg, 0.095 mmol, 95%. The compound was
stored under an atmosphere of CO.
class="Chemical">1H NMR (300 MHz,
class="Chemical">n class="Chemical">CD2Cl2): δ 7.57 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.38 (d, J = 7.7 Hz,
2H, CH-aromatic), 3.23 (br d, J = 12.7 Hz, 2H, CH2), 2.70 (sept, J = 6.7 Hz,
2H, CH(CH3)2), 2.47–1.85
(m, 14H, adamantyl CH and CH2), 1.44 (s, 6H, 2CH3), 1.35 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.33 (d, J = 6.7 Hz,
6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ
241.1 (C carbene), 182.4 (s, CO), 144.7 (o-C), 134.2 (Cipso), 131.2 (p-C), 125.7 (m-C), 80.8 (Cq), 65.4 (Cq), 47.9 (CH2), 38.4 (CH2), 36.9, 36.8,
33.8 (CH2), 29.1 (CH), 29.0, 27.7, 27.1,
26.6, 22.7 (CH3) ppm. IR (ATR, cm–1): 2968, 2903, 2183 (C≡O), 1541, 1450, 1387,
1262, 1195, 1097, 805, 651, 610, 583. Anal. Calcd for C28H39AuF6NOSb (838.33): C, 40.12; H, 4.69; N,
1.67. Found: C, 40.01; H, 4.59; N, 1.63.
Synthesis of [(AdCAAC)Au(CNBu)]SbF6 (17)
A Schlenk flask
was nclass="CellLine">charged with class="Chemical">n class="Chemical">(AdCAAC)AuCl (60.5 mg, 0.1 mmol), AgSbF6 (35 mg, 0.10 mmol), and CH2Cl2 (2 mL).
The resulting suspension was stirred for 1 h in the dark. The mixture
was filtered through a Celite pad (2 cm), which was washed with another
8 mL of CH2Cl2. The colorless solution was concentrated
to ca. 2 mL, and an excess of BuNC (22
μL, 0.2 mmol) was added, followed by stirring at room temperature
for 2 h. The product was precipitated with an excess of hexanes (15
mL), centrifuged, and washed with hexanes (5 mL). All volatiles were
removed under vacuum to give the complex as a white solid. Yield:
83.5 mg (0.094 mmol, 94%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.52 (t, J = 7.7
Hz, 1H, CH-aromatic), 7.33 (d, J = 7.7 Hz, 2H, CH-aromatic),
3.42 (br d, J = 12.6 Hz, 2H, CH2), 2.71 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.40–1.83 (m, 14H, adamantyl
CH and CH2), 1.48 (s, 9H, C(CH3)3), 1.39 (s, 6H, 2CH3), 1.33 (d, J = 6.7 Hz, 6H, CH(CH3)2),
1.31 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75
MHz, CD2Cl2): δ 246.2 (C carbene), 144.8
(o-C), 142.4 (br s, CNtBu) 134.5 (Cipso), 130.4 (p-C), 125.3
(m-C), 79.5 (Cq), 65.1 (Cq),
58.6 (br s, CNCMe3), 48.0 (CH2), 38.5 (CH2), 36.9, 36.1, 34.0 (CH2), 29.5
(CNC(CH3)3), 29.0 (CH), 28.9, 27.8, 26.8, 26.6, 22.7 (CH3) ppm. IR (ATR, cm–1): 2973, 2899, 2241
(CNtBu), 1538, 1450, 1373, 1194, 1147, 1097, 803, 776,
654, 523. Anal. Calcd for C32H48AuF6N2Sb (893.45): C, 43.02; H, 5.41; N, 3.14. Found: C, 43.13;
H, 5.49; N, 3.19.
Synthesis of (AdCAAC)AuCN (18)
nclass="Chemical">Trimethylsilyl cyanide
(20 μL, 0.150
mmol) was added to the solutioclass="Chemical">n of (class="Chemical">n class="Chemical">AdCAAC)AuOH (59 mg,
0.1 mmol) in 2 mL of toluene. The mixture was stirred at room temperature
overnight and concentrated under vacuum. The white residue was precipitated
with hexanes (6 mL). The resulting suspension was centrifuged. The
solid was washed with hexanes (3 × 5 mL) and dried under vacuum
to give a while solid. Yield: 57.5 mg, 0.095 mmol, 95%.
nclass="Chemical">(AdCAAC)AuCl (45 mg, 0.075 mmol),
class="Chemical">n class="Chemical">KCN (5 mg, 0.076 mmol) and 10 mL of ethanol were charged in a scintillation
vial and stirred overnight. All volatiles were evaporated, and the
white residue was extracted with CH2Cl2 (3 ×
5 mL). The combined extracts were filtered through a glass frit and
concentrated to ca. 0.5 mL. The product was precipitated with hexanes
(10 mL) and dried under vacuum. Yield: 42 mg (0.07 mmol, 92%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ
7.49 (t, J = 7.8 Hz, 1H,CH-aromatic), 7.30 (d, J = 7.8 Hz, 2H, CH-aromatic), 3.71(br d, J = 13.1 Hz, 2H, CH2), 2.72 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.32–1.79 (m, 14H, adamantyl CH and CH2), 1.37 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.34 (s, 6H, 2CH3), 1.30 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 253.1 (C carbene), 149.5 (CN), 144.9 (o-C), 134.8 (Cipso), 129.8
(p-C), 124.9 (m-C), 78.0 (Cq), 64.9 (Cq), 48.3 (CH2), 38.8 (CH2), 37.0, 35.6, 34.2 (CH2), 29.0 (CH), 28.9, 27.8, 27.1, 26.4, 22.7 (CH3) ppm. IR (ATR, cm–1): 2969, 2900, 2140 (C≡N),
1530, 1447, 1370, 1097, 934, 808, 727. Anal. Calcd For C28H39AuN2 (600.58): C, 56.00; H, 6.54; N, 4.66.
Found: C, 56.16; H, 6.61; N, 4.72.
Synthesis of [(AdCAAC)Au(norbornene)][tfaB(C6F5)3] (19)
A Schlenk
flask was nclass="CellLine">charged with (class="Chemical">n class="Chemical">AdCAAC)AuOAcf (60 mg,
0.088 mmol), B(C6F5)3 (90 mg, 0.176
mmol), norbornene (16.5 mg, 0.176 mmol), and dry CH2Cl2 (2 mL) under an argon atmosphere. The resulting suspension
was stirred for 1 h at −78 °C and left to warm to room
temperature while stirring overnight. The mixture was filtered through
a Celite pad (1 cm), which was washed with another 8 mL of CH2Cl2. The colorless solution was concentrated to
ca. 1 mL and the oily residue precipitated with an excess of hexanes
(15 mL). The solvents were decanted, and the residue was dissolved
in 0.5 mL of CH2Cl2 and precipitated with hexane
(15 mL). The oily colorless residue after decantation was dried under
vacuum to afford a white powder which was additionally dried under
vacuum overnight. Yield: 96 mg (0.074 mmol, 85%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2):
δ 7.50 (t, J = 7.8 Hz, 1H, CH-aromatic),
7.33 (d, J = 7.7 Hz, 2H, CH-aromatic), 5.83 (br s,
2H, Ha norbornene), 3.27 (br d, J = 12.2
Hz, 2H, CH2), 3.00 (br s, 2H, Hb norbornene), 2.71 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.42–1.75 (m, 18H,
adamantyl CH and CH2 overlapping with 4Hd norbornene),
1.44 (s, 6H, 2CH3), 1.32 (d, J = 6.7 Hz,
6H, CH(CH3)2), 1.29 (d, J = 6.7 Hz, 6H, CH(CH3)2), 0.60 (br d, 1H, 1J = 10.2 Hz,
Hc norbornene), 0.39 (br d, 1H, 1J = 10.2 Hz, Hc norbornene) ppm. 19F NMR (282
MHz, CD2Cl2): δ −76.9 (s, 3F, CF3), −135.09 (br d, 6F, JF–F = 19.5 Hz, o-C6F5), −161.7
(br t, 3F, JF–F = 19.5 Hz, p-C6F5), −166.7 (br t, 6F, JF–F = 19.5 Hz, m-C6F5) ppm. 13C{1H} NMR (75
MHz, CD2Cl2): δ (B–Cipso from C6F5 and C=O signals
were not observed) 246.8 (C carbene), 149.5–146.3 (d m,1JC–F= 248 Hz, CF), 144.6 (o-C), 140.6–137.3
(d m, 1JC–F= 248 Hz, CF), 138.2–135.0 (d m, 1JC–F= 252 Hz, CF), 135.3 (Cipso), 130.7 (p-C), 125.5 (m-C), 123.7 (CHa, norbornene), 115.4 (quart. 1JC–F= 288 Hz, CF3), 79.6
(Cq), 64.5 (Cq), 48.3 (CH2), 44.6
(CHb, norbornene), 43.9 (CH2c, norbornene),
38.4 (CH2), 36.9, 35.8, 33.9 (CH2), 29.1 (CH), 29.0, 27.8, 26.7, 26.5, 23.7 (CH2d, norbornene),
22.8 (CH3) ppm. IR (ATR, cm–1): 2906, 1749 (C=O), 1643 (C=C norbornene), 1514, 1465,
1374, 1281, 1187, 1153, 1093, 977, 851, 807, 680. Anal. Calcd for
C54H49AuBF18NO2 (1293.71):
C, 50.13; H, 3.82; N, 1.08. Found: C, 50.32; H, 3.61; N, 1.01.
Reaction
of (AdCAAC)AuCl with PhICl2 at
20 °C without Light Protection
A mixture of nclass="Chemical">(AdCAAC)AuCl (61 mg, 0.10 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">PhICl2 (30 mg, 0.11 mmol)
in 5 mL of CH2Cl2 was stirred overnight at room
temperature. The yellow solution was concentrated to ca. 0.3 mL. Adding
Et2O (10 mL) gave a yellow precipitate, which was washed
with Et2O (2 × 5 mL) and dried under vacuum: yield
63 mg. Crystallization by layering a CH2Cl2 solution
with hexanes led to the formation of two types of crystals, the structures
of which were confirmed by X-ray diffraction. A small amount of colorless
needles was identified as the dichloroaurate(I) salt [(AdCAAC-Cl)][AuCl2] (20a), while the major component
of yellow prisms turned out to be the cocrystallization product {2[(AdCAAC-Cl)][AuCl4]·(AdCAAC)AuCl3}. NMR spectroscopy showed two sets of ligand
signals in an approximate 2:1 ratio, which were assigned on the basis
of the known signals for the pure salt [(AdCAAC-Cl)]AuCl4 (20b) and the complex AdCAACAuCl3 (25). The 1H and 13C NMR
spectra of the two salts [(AdCAAC-Cl)]AuCl2 and
[(AdCAAC-Cl)]AuCl4 are essentially identical.
Elemental analysis was not carried out due to formation of a product
mixture.
Synthesis of [(AdCAAC-Cl)][AuCl4] (20b)
A solution of class="Chemical">(AdCAAC)AuCl (61 mg,
0.1 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">PhICl2 (58 mg, 0.21 mmol) in 5 mL of CH2Cl2 was stirred for 3 h without light protection.
A yellow solution resulted, which was concentrated to ca. 0.3 mL.
The addition of Et2O (10 mL) gave a yellow precipitate,
which was washed with Et2O (2 × 5 mL) and dried under
vacuum. Yield: 74 mg, 0.098 mmol, 98%.
class="Chemical">1H NMR (300
MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.66 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.46 (d, J = 7.7 Hz,
2H, CH-aromatic), 2.92 (s, 2H, CH2, adamantyl), 2.67 (br
d, J = 13.0 Hz, 2H, CH2), 2.45 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.39–1.89 (m, 12H, adamantyl
CH and CH2), 1.58 (s, 6H, 2CH3), 1.38 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.20 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR
(75 MHz, CD2Cl2): δ 188.5 (C–Cl),
143.8 (o-C), 132.7 (p-C), 128.0
(Cipso), 126.5 (m-C), 79.2 (Cq), 60.8 (Cq), 47.8 (CH2), 38.0 (CH2), 37.1, 34.1, 32.1 (CH2), 29.9 (CH),
28.5, 26.4, 25.8, 23.1 (CH3) ppm. Anal.
Calcd for C27H39AuCl5N (751.83):
C, 43.13; H, 5.23; N, 1.86. Found: C, 42.96; H, 5.28; N, 2.00.
Synthesis
of (AdCAAC)AuBr
A suspension of
class="Chemical">(AdCAAC)AuCl (61 mg, 0.10 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">LiBr (88 mg, 1 mmol)
in 10 mL of acetone was stirred for 24 h at room temperature. The
solvent was removed under vacuum. The white residue was extracted
with CH2Cl2 (2 × 10 mL) and filtered through
Celite (1 cm). All volatiles were removed under vacuum to give an
off-white solid with one solvate molecule of CH2Cl2. Yield: 72.5 mg (0.098 mmol, 98%).
class="Chemical">1H NMR
(300 MHz, class="Chemical">n class="Chemical">CDCl3): δ 7.41 (t, J =
7.7 Hz, 1H, CH-aromatic), 7.24 (d, J = 7.7 Hz, 2H,
CH-aromatic), 5.29 (s, 2H, solvent molecule CH2Cl2), 4.02 (br d, J = 12.6 Hz, 2H, CH2), 2.74 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.35–1.78 (m, 14H,
adamantyl CH and CH2), 1.42 (d, J = 6.7
Hz, 6H, CH(CH3)2), 1.34 (s,
6H, 2CH3), 1.29 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ 242.6 (C carbene), 144.8
(o-C), 135.1 (Cipso), 129.7 (p-C), 124.9 (m-C), 76.7 (Cq), 63.7 (Cq), 53.4 (solvent molecule CH2Cl2), 48.6
(CH2), 38.9 (CH2), 37.0, 35.1, 34.5 (CH2), 29.1 (CH), 29.0, 27.5, 27.1, 26.8, 23.0
(CH3) ppm. Anal. Calcd for C27H39AuBrN·CH2Cl2 (739.40): C,
45.48; H, 5.59; N, 1.89. Found: C, 45.57; H, 5.67; N, 2.01.
Reaction
of (AdCAAC)AuBr with CsBr3
A suspension
of nclass="Chemical">(AdCAAC)AuBr·class="Chemical">n class="Chemical">CH2Cl2 (74 mg,
0.10 mmol) and CsBr3 (38 mg, 0.10 mmol)
in 5 mL of CH2Cl2 was stirred for 20 min at
−78 °C and warmed to room temperature with stirring for
1 h. The suspension was filtered through a glass frit and the filtrate
concentrated to ca. 0.3 mL. An orange solid was precipitated with
hexanes (10 mL) and dried under vacuum. Yield: 80 mg. Recrystallization
by layering a CH2Cl2 solution with hexanes led
to the formation of two types of crystals, which were identified by
X-ray diffraction: a larger amount of colorless prisms of [(AdCAAC-Br)]+[AuBr2]− (21a) and a small amount of red prisms of [(AdCAAC-Br)]+[AuBr4]− (21b).
Both give identical 1H and 13C NMR spectra.
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ
7.65 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.46 (d, J = 7.7 Hz, 2H, CH-aromatic), 2.93 (s, 2H, CH2, adamantyl) overlapping with 2.91 (br d, J = 13.0
Hz, 2H, CH2), 2.44 (sept, J = 6.7 Hz, 2H, CH(CH3)2),
2.36–1.89 (m, 12H, adamantyl CH and CH2), 1.59 (s,
6H, 2CH3), 1.38 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.26 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 186.0 (C–Br), 143.6 (o-C), 132.5
(p-C), 130.4 (Cipso), 126.7 (m-C), 80.8 (Cq), 62.7 (Cq), 48.0 (CH2), 38.3 (CH2), 37.1, 34.3, 31.9 (CH2), 29.8
(CH), 28.7, 26.5, 25.9, 23.5 (CH3) ppm. Elemental analysis was not carried out due to formation
of a product mixture.
Synthesis of [(Me2CAAC)2Au]Cl (22)
A Schlenk flask was class="CellLine">charged with class="Chemical">n class="Chemical">Me2CAAC (0.39
g, 1.36 mmol), (Me2S)AuCl (0.195 g, 0.66 mmol), and 20
mL of THF under an argon atmosphere. The mixture was stirred at room
temperature for 18 h. All volatiles were removed under vacuum and
the residue was washed with hexanes (3 × 10 mL). The product
was dissolved in CH2Cl2 (3 mL) and precipitated
with hexanes (40 mL). All volatiles were evaporated. The residue was
dried under vacuum to give a white solid. Yield: 510 mg (0.635 mmol,
96%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.42 (t, J = 7.7 Hz, 1H, CH-aromatic),
7.23 (d, J = 7.7 Hz, 2H, CH-aromatic), 2.59 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.04 (br s, 2H, CH2), 1.31
(s, 6H, 2CH3), 1.24 (d, J = 6.7 Hz, 6H,
CH(CH3)2), 1.20 (s, 6H, 2CH3), 1.01 (br d, J = 6.7 Hz, 6H, CH(CH3)2). 13C{1H} NMR (75 MHz, CD2Cl2): δ 250.6 (C carbene),
144.6 (o-C), 133.5 (C), 130.1 (p-C), 125.1 (m-C), 82.3
(Cq), 54.6 (Cq), 49.3 (CH2), 28.9
(CH), 28.8, 28.4, 26.7, 22.6 (CH3). Anal. Calcd for C40H62AuClN2 (803.35): C, 59.80; H, 7.78; N, 3.49. Found: C, 59.49; H, 7.57;
N, 3.31.
Synthesis of [AuCl2(Me2CAAC)2]Cl (23)
A mixture of nclass="Chemical">[Au(Me2CAAC)2]Cl (80 mg, 0.10 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">PhICl2 (28 mg, 0.10
mmol) in 5 mL of CH2Cl2 was stirred in the dark
for 6 h at 0 °C and warmed to room temperature. The colorless
solution was concentrated to ca. 0.3 mL. Addition of Et2O (10 mL) gave an off-white precipitate, which was washed with Et2O (2 × 5 mL) and dried under vacuum. Yield: 91 mg (0.94
mmol, 94%). Crystallization by layering a CH2Cl2 solution with hexanes in the dark led to the formation of large
colorless prisms and negligible amounts of yellow prisms, which were
identified by X-ray diffraction: the colorless prisms as [AuCl2(Me2CAAC)2]Cl·CH2Cl2 (23·CH2Cl2) and yellow
prisms as [Au(Me2CAAC)2]AuCl4.
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ
7.42 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.23 (d, J = 7.7 Hz, 2H, CH-aromatic), 2.58 (sept, J = 6.7 Hz, 2H, CH(CH3)2),
2.04 (br s, 2H, CH2), 1.31 (s, 6H, 2CH3), 1.23 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.19 (s, 6H, 2CH3), 1.01 (br
s, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 250.6 (C carbene), 144.6 (o-C), 133.4
(Cipso), 130.1 (p-C), 125.1 (m-C), 82.3 (Cq), 54.6 (Cq), 49.3 (CH2), 28.9 (CH), 28.8, 28.4, 26.7, 22.6 (CH3) ppm. Anal. Calcd for C40H62AuCl3N2·CH2Cl2 (959.18):
C, 51.34; H, 6.73; N, 2.92. Found: C, 51.64; H, 6.96; N, 3.14.
Reaction
of [Au(Me2CAAC)2]Cl with CsBr3 at
−78 °C
A mixture of nclass="Chemical">[Au(Me2CAAC)2]Cl (89 mg, 0.10 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">CsBr3 (38
mg, 0.10 mmol) in 5 mL of CH2Cl2 was stirred
for 20 min at −78 °C and warmed to room temperature with
stirring for 1 h. The orange-red solution was concentrated to ca.
0.3 mL. An orange solid was precipitated with hexanes (10 mL) and
dried under vacuum. Yield: 95 mg. Crystallization by layering a CH2Cl2 solution with hexanes gave two type of crystals,
which were identified by X-ray diffraction as orange prisms of [Au(Me2CAAC)2]Br3 (24a) and
red prisms of [Au(Me2CAAC)2]AuBr4 (24b). Both give identical 1H NMR spectra.
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ
7.43 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.25 (d, J = 7.7 Hz, 2H, CH-aromatic), 2.61 (sept, J = 6.7 Hz, 2H, CH(CH3)2),
2.06 (br s, 2H, CH2), 1.33 (s, 6H, 2CH3), 1.26 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.22 (s, 6H, 2CH3), 1.03 (br
d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 250.6 (C carbene), 144.6 (o-C), 133.5
(Cipso), 130.1 (p-C), 125.1 (m-C), 82.4
(Cq), 54.6 (Cq), 49.5 (CH2), 28.9
(CH), 28.8, 28.5, 26.7, 22.6 (CH3) ppm. Elemental analysis was not carried out due to formation
of a product mixture.
Synthesis of [Au(Me2CAAC)2]ClI2 (24c)
A solution of
class="Chemical">[Au(Me2CAAC)2]Cl (80 mg, 0.10 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">I2 (26 mg, 0.10 mmol)
in 3 mL of CH2Cl2 was stirred for 1 h at 0 °C
and warmed to room temperature with stirring for 1 h. Addition of
hexanes (15 mL) led to the precipitation of a brown product, which
was centrifuged, washed with 5 mL of Et2O, and dried under
vacuum. Yield: 102.5 mg (0.097 mmol, 97%).
class="Chemical">1H NMR
(300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.44 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.24 (d, J = 7.7 Hz, 2H, CH-aromatic), 2.59 (sept, J = 6.7
Hz, 2H, CH(CH3)2), 2.06 (br
s, 2H, CH2), 1.32 (s, 6H, 2CH3), 1.25 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.21 (s, 6H, 2CH3), 1.02 (br
d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 250.6 (C carbene), 144.6 (o-C), 133.5 (Cipso), 130.1 (p-C), 125.1 (m-C), 82.4 (Cq), 54.6 (Cq), 49.4 (CH2), 28.9 (CH), 28.8,
28.5, 26.7, 22.6 (CH3) ppm. Anal. Calcd
for C40H62AuClI2N2 (1057.16):
C, 45.45; H, 5.91; N, 2.65. Found: C, 45.37; H, 5.83; N, 2.59.
Synthesis
of (AdCAAC)AuCl3 (25)
All operations have to be performed with minimum exposure
to light. A scintillation vial was nclass="CellLine">charged with class="Chemical">n class="Chemical">(AdCAAC)AuCl
(61 mg, 0.10 mmol) and PhICl2 (29 mg, 0.105 mmol) and wrapped
in aluminum foil. Chilled CH2Cl2 (5 mL) was
added and resulting solution stirred for 6 h at 0 °C in the dark.
A slightly yellow solution resulted, which was concentrated to ca.
0.3 mL. The addition of Et2O (15 mL) gave a pale yellow
precipitate which was washed with Et2O (2 × 5 mL)
and dried under vacuum. Yield: 64 mg (0.095 mmol, 95%). 1H NMR (300 MHz, CD2Cl2): δ 7.52 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.38 (d, J = 7.7 Hz, 2H, CH-aromatic), 3.33 (br d, J = 13.2
Hz, 2H, CH2), 3.04 (sept, J = 6.7 Hz, 2H, CH(CH3)2),
2.54–1.82 (m, 14H, adamantyl CH and CH2), 1.55 (s,
6H, 2CH3), 1.48 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.27 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 218.8 (C carbene), 146.2 (o-C), 133.5
(p-C), 130.9 (Cipso), 126.7 (m-C), 82.1 (Cq), 69.1 (Cq), 47.6 (CH2), 38.0 (CH2), 37.7, 35.3, 34.5 (CH2), 30.1
(CH), 29.0, 27.1, 26.6, 26.1 (CH3). Anal. Calcd for C27H39AuCl3N (680.92): C, 47.62; H, 5.77; N, 2.06. Found: C, 47.69; H, 5.72;
N, 2.12.
Synthesis of (AdCAAC)AuI
A mixture of [class="Chemical">Au(AdCAAC)(Cl)]
(61 mg, 0.10 mmol) aclass="Chemical">nd class="Chemical">n class="Chemical">NaI (150 mg, 1 mmol) in 10 mL of acetone was
stirred for 24 h at room temperature. The solvent was removed under
vacuum. The white residue was extracted with CH2Cl2 (2 × 10 mL) and the solution filtered through Celite
(1 cm). All volatiles were removed under vacuum to give an off-white
solid with 0.5 CH2Cl2 as a solvate molecule.
Yield: 73.5 mg (0.098 mmol, 98%).
class="Chemical">1H NMR (300 MHz,
class="Chemical">n class="Chemical">CD2Cl2): δ 7.48 (t, J = 7.7 Hz, 1H, CH-aromatic), 7.29 (d, J = 7.7 Hz,
2H, CH-aromatic), 5.33 (s, 1H, solvent molecule 0.5CH2Cl2) 3.98 (br d, J = 12.6 Hz, 2H, CH2), 2.78 (sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.38–1.81 (m, 14H,
adamantyl CH and CH2), 1.41 (d, J = 6.7
Hz, 6H, CH(CH3)2), 1.36 (s,
6H, 2CH3), 1.30 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 247.5 (C carbene),
144.9 (o-C), 135.1 (Cipso), 129.6 (p-C), 124.8 (m-C), 77.1 (Cq),
63.9 (Cq),, 48.4 (CH2), 38.8 (CH2), 37.0, 34.9, 34.3 (CH2), 29.0 (CH),
28.9, 27.8, 27.2, 26.4, 22.8 (CH3) ppm.
Anal. Calcd for C27H39AuIN·0.5CH2Cl2 (743.94): C, 44.40; H, 5.42; N, 1.88. Found: C, 44.33;
H, 5.48; N, 1.93.
Synthesis of (AdCAAC)AuI·I2 (26)
A mixture of (class="Chemical">AdCAAC)class="Chemical">n class="Chemical">AuI·0.5CH2Cl2 (74 mg, 0.10 mmol) and I2 (26 mg,
0.10 mmol) in 5 mL of CH2Cl2 was stirred for
20 min at −78 °C and warmed to room temperature with stirring
for 2 h to give a dark red solution. The solvent was removed under
vacuum and the residue washed with hexanes (3 × 6 mL) and dried
under vacuum to afford a dark red solid. Yield: 92 mg (0.097 mmol,
97%).
class="Chemical">1H NMR (300 MHz, class="Chemical">n class="Chemical">CD2Cl2): δ 7.50 (t, J = 7.7 Hz, 1H, CH-aromatic),
7.29 (d, J = 7.7 Hz, 2H, CH-aromatic), 3.96 (br d, J = 12.6 Hz, 2H, CH2), 2.77
(sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.38–1.82 (m, 14H, adamantyl CH and
CH2), 1.41 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.36 (s, 6H, 2CH3), 1.30 (d, J = 6.7 Hz, 6H, CH(CH3)2) ppm. 13C{1H} NMR
(75 MHz, CD2Cl2): δ 246.6 (C carbene),
144.8 (o-C), 135.1 (Cipso), 129.8 (p-C), 125.0 (m-C), 77.2 (Cq),
63.9 (Cq), 48.4 (CH2), 38.8 (CH2),
37.0, 35.1, 34.3 (CH2), 29.0 (CH), 28.9,
27.8, 27.2, 26.5, 22.8 (CH3) ppm. Anal.
Calcd for C27H39AuI3N (955.28): C,
33.95; H, 4.11; N, 1.47. Found: C, 33.81; H, 4.02; N, 1.39.
X-ray
Crystallography
Crystals suitable for X-ray study
were obtained by layering of a nclass="Chemical">CH2Cl2 solutioclass="Chemical">n
with class="Chemical">n class="Chemical">hexanes, with the exception of complex 17 (1,2-difluorobenzene/hexanes).
Crystals were mounted in oil on glass fibers and fixed in the cold
nitrogen stream on a diffractometer. X-ray diffraction experiments
were carried out with an Oxford Diffraction Xcalibur-3/Sapphire3-CCD
diffractometer, using graphite-monochromated Mo Kα radiation
(λ = 0.71073 Å) at 140 K. Data were processed using the
CrystAlisPro-CCD and -RED software.[48] The
principal crystallographic data and refinement parameters are given
in Table S1 (Supporting Information). The
CH2 (C3 atom) and methyl groups (C17 and C18 atoms) were
disordered over two positions with occupancies of 0.65/0.35 and 0.62/0.38,
respectively. The Cl1 and I2 atoms for complex 24c were
disordered into two positions linked by a center of inversion with
equal occupancies. The complex [{(AdCAAC)Au}3(μ3-O)]+OH– crystallizes
with two independent molecules and half of a benzene molecule. The
oxygen atoms of the hydroxidecounteranion for [{(AdCAAC)Au}3(μ3-O)]+OH– were
not refined anisotropically, due to disorder problems masked by the
presence of the disordered solvent molecules. For the final refinement,
the contribution of severely disordered CH2Cl2 molecules in crystals of 7, 14, and [{(AdCAAC)Au}3(μ3-O)]+OH– were removed from the diffraction data with PLATON/SQUEEZE.[49,50] The structures were solved by direct methods and refined by the
full-matrix least squares against F2 in
an anisotropic (for non-hydrogen atoms) approximation. All hydrogen
atom positions were refined in an isotropic approximation in the “riding”
model with the Uiso(H) parameters equal
to 1.2[Ueq(C)] and for methyl groups equal to 1.5[Ueq(C)], where U(C) and U(C) are respectively the equivalent thermal parameters of the
carbon atoms to which the corresponding H atoms are bonded. The hydrogen
atom of the hydroxidecounteranion in [{(AdCAAC)Au}3(μ3-O)]+OH– was
not located. All calculations were performed using the SHELXTL software.[51] Intensities for complex 14 and
[{(AdCAAC)Au}3(μ3-O)]+OH– were collected at 100(2) K on a Bruker-Nonius
Roper CCD diffractometer, equipped with Mo Kα radiation and
a graphite monochromator at the EPSRC National Crystallography service,
Southampton, U.K.[52] Data were processed
using CrystalClear-SM Expert 3.1 b21 (Rigaku, 2012) programs.
Authors: Vincent Lavallo; Guido D Frey; Bruno Donnadieu; Michele Soleilhavoup; Guy Bertrand Journal: Angew Chem Int Ed Engl Date: 2008 Impact factor: 15.336
Authors: Liqun Jin; David S Weinberger; Mohand Melaimi; Curtis E Moore; Arnold L Rheingold; Guy Bertrand Journal: Angew Chem Int Ed Engl Date: 2014-07-01 Impact factor: 15.336
Authors: Christa Hirtenlehner; Charlotte Krims; Johanna Hölbling; Manuela List; Manfred Zabel; Michel Fleck; Raphael J F Berger; Wolfgang Schoefberger; Uwe Monkowius Journal: Dalton Trans Date: 2011-08-30 Impact factor: 4.390
Authors: Olivier Back; Martin Henry-Ellinger; Caleb D Martin; David Martin; Guy Bertrand Journal: Angew Chem Int Ed Engl Date: 2013-01-31 Impact factor: 15.336
Authors: Vincent Lavallo; Guido D Frey; Shazia Kousar; Bruno Donnadieu; Guy Bertrand Journal: Proc Natl Acad Sci U S A Date: 2007-08-13 Impact factor: 11.205
Authors: Qinying Gu; Florian Chotard; Julien Eng; Antti-Pekka M Reponen; Inigo J Vitorica-Yrezabal; Adam W Woodward; Thomas J Penfold; Dan Credgington; Manfred Bochmann; Alexander S Romanov Journal: Chem Mater Date: 2022-08-04 Impact factor: 10.508
Authors: Alexander S Romanov; Saul T E Jones; Qinying Gu; Patrick J Conaghan; Bluebell H Drummond; Jiale Feng; Florian Chotard; Leonardo Buizza; Morgan Foley; Mikko Linnolahti; Dan Credgington; Manfred Bochmann Journal: Chem Sci Date: 2019-11-13 Impact factor: 9.825
Authors: Alexander S Romanov; Dawei Di; Le Yang; Julio Fernandez-Cestau; Ciaran R Becker; Charlotte E James; Bonan Zhu; Mikko Linnolahti; Dan Credgington; Manfred Bochmann Journal: Chem Commun (Camb) Date: 2016-04-18 Impact factor: 6.222
Authors: Ekaterina S Smirnova; José M Muñoz Molina; Alice Johnson; Nuno A G Bandeira; Carles Bo; Antonio M Echavarren Journal: Angew Chem Int Ed Engl Date: 2016-05-11 Impact factor: 15.336
Chart I
Scheme 1
Figure 1
Scheme 2
Scheme 3
Figure 2
Scheme 4
Figure 3
Scheme 5
Figure 4
Figure 5
Figure 6
Figure 7