Group 9 and 10 Metal Complexes of an Ylide-Substituted Phosphine: Coordination versus Cyclometalation and Oxidative Addition.

Ylide-substituted phosphines (YPhos) have been shown to be excellent ligands for several transition metal catalyzed reactions. Investigations of the coordination behavior of the YPhos ligand YSPPh2 (1) [with YS = (Ph3P)(SO2Tol)C] toward group 9 and 10 metals revealed a surprisingly diverse coordination chemistry of the ligand. With Ni(CO)4, the formation of a di- as well as tricarbonyl complex is observed depending on the reaction conditions. In [( κP,η 2 -benzene-1)Ni(CO)2] the phosphine ligand also coordinates via a phosphonium bound phenyl group to the metal leading to a unique nickel η 2 -arene interaction, which can be viewed as an intermediate state toward P-C bond activation. Full cleavage of the P-C bond takes place with [Rh(COD)Cl]2 leading to a complex salt with [( κP,κO-1)Rh(COD)]+ as cation and a dirhodium trichloride complex anion. Here, YSPPh2 underwent P-C bond cleavage to thus act as an anionic diphosphine ligand. In contrast, in [( κP,κO-1)Rh(COD)]+ as well as [( κP,κO-1)Rh(CO)Cl], formed from the reaction of 1 with [Rh(CO)2Cl]2, the YPhos ligand acts as bidentate ligand complexing the metal via the phosphine and sulfonyl moiety with an intact PPh3 unit. A further type of coordination is observed with [Ir(COD)Cl]2. Here, phosphine coordination is accompanied by C-H activation at one of the phosphonium bound phenyl groups leading to a cyclometalated complex.

Introduction

pan class="Chemical">Phosphines are ubiquitous in n>an class="Chemical">coordination chemistry and homogeneous catalysis. For many decades, their further development by changing the electronic and steric properties has been part of vivid research activities.[1] While monophosphines are typically considered as simple L donor ligands, their coordination chemistry can be quite versatile. Depending on the ligand architecture, the phosphine coordination can be accompanied by further ligand metal interactions. In the simplest case, this might be the coordination of further donor sites in the ligand system. However, also cyclometalation processes—typically via C–H activation of an adjacent phenyl group—have often been observed for aryl phosphines[2] and are frequently used for the synthesis of pincer complexes.[3,4] Furthermore, P–C bond splitting reactions have been reported particularly at electron-deficient metal species[5] and also catalytically been applied in coupling reactions.[6] Here, usually the formation of an intermediate phosphonium species is involved.

Repan class="Chemical">cently, we reported on n>an class="Chemical">ylide-substituted phosphines (YPhos), formed by incorporation of an ylide group directly at the phosphorus center.[7] Due to the strong electron donation from the ylide these phosphines become more electron-rich than classical phosphines with donor strengths comparable to those of N-heterocyclic carbenes.[8] The YPhos ligands turned out to be ideal supporting ligands for transition metal catalysts and showed excellent performance in gold catalyzed hydroamination reactions as well as Buchwald Hartwig aminations under mild reaction conditions.[9] Besides their remarkable donor strength, the unique architecture of the phosphines was found to be decisive for their activity. In case of palladium catalysis, an agostic interaction between the metal and a cyclohexyl group of a PCy3 phosphonium moiety was observed in the catalytically active species, resulting in a further stabilization of the complex. In gold catalysis with the triphenylphosphonium substituted ligands, however, we suggested the presence of a stabilizing Au-arene interaction similar to the Buchwald-type biarylphophine ligands.[10] These observations suggested a rich coordination chemistry of these PPh3 substituted YPhos ligands (Figure ), which we set out to further explore.

Figure 1

Possible coordination and reactive sites in the ylide-functionalized phosphine 1.

Results and Discussions

We started our investigations with the pan class="Chemical">sulfonyl-funn>an class="Chemical">ctionalized YPhos ligand YSPPh2 (1), which showed a high activity in gold catalysis. We particularly focused on group 9 and 10 metals due to their importance in homogeneous catalysis. Preliminary attempts to determine the Tolman electronic parameter of 1 via synthesis of the corresponding nickel tricarbonyl complex gave no reliable data.[7] Thus, the isolation of the corresponding complex was attempted. Treatment of YSPPh2 with 1 equiv of [Ni(CO)4] at first resulted in the expected formation of the complex [(κP-1)Ni(CO)3] as evidenced by NMR spectroscopy (Scheme ). As such, two new doublets were observed in the 31P{1H} NMR spectrum at δP = 18.6 and 20.7 ppm with a coupling constant of 2JPP = 54.6 Hz. However, removal of the solvent in vacuo resulted in the disappearance of these signals and the appearance of a new, somewhat broadened signal at 23.8 ppm, which we assigned to a dicarbonyl complex. Remarkably, this reaction revealed to be reversible. Applying an atmosphere of CO resulted in the reformation of [(κP-1)Ni(CO)3] and the appearance of its corresponding two doublets in the 31P{1H} NMR spectrum. At higher CO pressures even the cleavage of the phosphine ligand and reformation of [Ni(CO)4] was observed. Due to the equilibrium and further decomposition of [1·Ni(CO)2] no full characterization of the complexes was possible. However, crystallization allowed the isolation of both complexes in the solid state (Figure ). Diffusion of pentane into a benzene solution gave way to the nickel dicarbonyl complex, while crystallization under a CO atmosphere allowed the isolation of [(κP-1)Ni(CO)3]. Both molecular structures are depicted in Figure (monoclinic space group P21/c). While the tricarbonyl complex shows the expected coordination of the YPhos ligand solely via the phosphine unit, the dicarbonyl complex features an additional η2-coordination of the nickel atom by one of the phenyl groups of the triphenylphosphonium moiety. The structure of [(κP,η-benzene-1)Ni(CO)2] ([1·Ni(CO)2]) contains two molecules in the asymmetric unit, which both feature the same coordination mode. To the best of our knowledge such a secondary arene interaction with an aryl phosphonium moiety has never been observed for nickel.[11] This interaction in [1·Ni(CO)2] becomes evident from short Ni–C interactions to the ipso and ortho carbon atoms, which range between 2.243(2) and 2.404(2) Å. It is interesting to note that the two molecules in the asymmetric unit show quite different Ni–C distances, which suggests that the interaction is only weak and sensitive to packing effects. Due to the Ni arene interaction the involved C–C bond is slightly elongated (1.415(2) and 1.403(2) Å) in comparison to the other C–C bonds in the phenyl groups (approximately 1.39 Å). The arene Ni interaction also results in a distinct bending of the phenyl ring which becomes evident from the C–C–C-P dihedral angle of 167.4(2)° and 159.9(2)°, which clearly differs from the ideal 180°. The P2–Ni distances of 2.233(1) and 2.215(1) Å are comparable to those for reported nickel(0) phosphine complexes.[12]

Scheme 1

Preparation of Nickel Carbonyl Complexes of YSPPh2 (1) and YSPMe2 (2)

Figure 2

Molecular structures of the nickel carbonyl complexes of YSPPh2 (1) and YSPMe2 (2). Hydrogen atoms and solvent molecules are omitted for clarity; only one of the two molecules in the asymmetric unit is shown. Displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: [1·Ni(CO)3], Ni–C41 1.794(2), Ni–C39 1.806(2), Ni–C40 1.806(2), Ni–P2 2.2588(5), C1–S 1.7131(16), C1–P1 1.7431(17), C1–P2 1.7945(16), S(1)–C(1)–P(1) 112.51(9); [1·Ni(CO)2], P(1)–C(1) 1.7342(15), S(1)–C(1) 1.7130(16), C(1)–P(2) 1.7704(16), Ni(1)–P(2) 2.2149(5), Ni(1)–C(9) 2.2426(15), Ni(1)–C(10) 2.2814(15), C(9)–C(10) 1.415(2), S(1)–C(1)–P(2) 118.39(9), P(1)–C(1)–P(2) 116.46(9). 2·[Ni(CO)3], P(1)–C(1) 1.729(4), S(1)–C(1) 1.726(4), C(1)–P(2) 1.807(4), Ni(1)–P(2) 2.2737(13), Ni(1)–C(29) 1.795(5), Ni(1)–C(30) 1.806(6), Ni(1)–C(31) 1.783(6), O(3)–C(29) 1.134(6), O(4)–C(30) 1.137(6), O(5)–C(31) 1.144(6), S(1)–C(1)–P(1) 118.4(2), P(1)–C(1)–P(2) 119.1(2).

Molepan class="Chemical">cular strun>an class="Chemical">ctures of the nickel carbonyl complexes of YSPPh2 (1) and YSPMe2 (2). Hydrogen atoms and solvent molecules are omitted for clarity; only one of the two molecules in the asymmetric unit is shown. Displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: [1·Ni(CO)3], Ni–C41 1.794(2), Ni–C39 1.806(2), Ni–C40 1.806(2), Ni–P2 2.2588(5), C1–S 1.7131(16), C1–P1 1.7431(17), C1–P2 1.7945(16), S(1)–C(1)–P(1) 112.51(9); [1·Ni(CO)2], P(1)–C(1) 1.7342(15), S(1)–C(1) 1.7130(16), C(1)–P(2) 1.7704(16), Ni(1)–P(2) 2.2149(5), Ni(1)–C(9) 2.2426(15), Ni(1)–C(10) 2.2814(15), C(9)–C(10) 1.415(2), S(1)–C(1)–P(2) 118.39(9), P(1)–C(1)–P(2) 116.46(9). 2·[Ni(CO)3], P(1)–C(1) 1.729(4), S(1)–C(1) 1.726(4), C(1)–P(2) 1.807(4), Ni(1)–P(2) 2.2737(13), Ni(1)–C(29) 1.795(5), Ni(1)–C(30) 1.806(6), Ni(1)–C(31) 1.783(6), O(3)–C(29) 1.134(6), O(4)–C(30) 1.137(6), O(5)–C(31) 1.144(6), S(1)–C(1)–P(1) 118.4(2), P(1)–C(1)–P(2) 119.1(2).

In pan class="Chemical">contrast to n>an class="Chemical">YSPPh2, the less bulky methyl-substituted ligand YSPMe2 (2) selectively gives way to the tricarbonyl complex [(κP-YSPMe2)Ni(CO)3] upon treatment with Ni(CO)4 (Scheme ). No further loss of CO was observed, even upon drying of the solid in vacuo. [(κP-2)Ni(CO)3] could be isolated as yellow solid in 61% yield and fully characterized. The complex exhibits two sharp doublets at −11.8 and +20.3 ppm with a coupling constant of 75.7 Hz in the 31P{1H} NMR spectrum. The signal of the carbon atom of the carbonyl ligands resonates at 196.2 ppm, in the typical range of known terminal nickel carbonyls.[13] The CO stretching frequency of 2060.2 cm–1 determined by IR spectroscopy confirms the strong donor property of the YPhos ligand, as recently reported based on the [LRh(acac)Cl] complex.[7] The stronger donor property of 2 compared to 1 (TEP(1) = 2066.5 cm–1) is probably also the reason for the selective formation of the tricarbonyl complex. Due to the resulting higher electron density at nickel the carbonyl ligands should be stronger bound in [(κP-2)Ni(CO)3] than in [(κP-1)Ni(CO)3] and thus more difficult to be replaced by arene coordination. Single crystals of [(κP-2)Ni(CO)3] were obtained by diffusion of hexane into a benzene solution (Figure ). The complex crystallizes in the monoclinic space group C/c with two molecules in the asymmetric unit. In the structure of [(κP-2)Ni(CO)3], the YPhos ligand adopts a syn-arrangement with the [Ni(CO)3] fragment being oriented on the same side as the bulky PPh3 moiety (Figure ). This results in steric congestion, which becomes evident from the structural parameters. As such, the geometry around the nickel atom strongly deviates from an ideal tetrahedron with the angles around nickel ranging from 99.7(2) to 116.5(2)°. The Ni–P distance of 2.2737(13) Å is the longest in the series of compounds despite the smaller size of the ligand itself (% Vbur(1) = 49.6; % Vbur(2) = 46.2). In contrast, an antiarrangement is observed in [(κP-1)Ni(CO)3] in the solid state.

Figure 3

syn- and anti-conformers for [(κP-2)Ni(CO)3].

It is so far unpan class="Chemical">clear why the n>an class="Chemical">nickel complex of the YsPMe2 ligand prefers the syn-arrangement in the solid state, while its phenyl analogue prefers the anti-conformer. It is likely that this is only due to packing effects, since no indication for the formation of stable syn- or anti-conformers was found in solution. As such, the coupling constants for both complexes are in between the expected range for the different conformers.[7] This suggests, that in contrast to the free ligands, which showed both (1) or only the syn-conformer (2) in solution, rapid rotation about the P–C bond takes place in the metal complexes. This can easily be understood, since the conformers are the result of the repulsion between the two lone pairs at the carbon and phosphorus atoms. This repulsion should become decisively smaller upon coordination of the phosphine to the metal and the involvement of the lone pair in the metal bonding.

The η2 coordination of one of the n>an class="Chemical">phenyl groups of the PPh3 moiety in YsPPh2 to nickel can be viewed as a first step for P–C bond activation and the transfer of the phenyl group to nickel, although no P–C bond elongation was observed. This is in contrast to the observations previously made in the palladium chemistry of other YPhos ligands. Here, YPhos ligands with triphenylphosphonium groups readily reacted with different Pd(0) precursors under P–C bond cleavage.[9] Any attempts to isolate corresponding palladium(0) complexes with YsPPh2 failed. For example, treatment of 1 with Pd2dba3 (dba = dibenzylideneacetone) resulted in unselective decomposition reactions, including P–C bond activation. This was confirmed by the isolation of small amounts of single crystals of palladium complex 3 with two monoanionic diphosphine ligands (Figure ). These ligands are formed via cleavage of one of the P–CPh bonds of the PPh3 moiety. Presumably, the cleaved phenyl group adds to the dba ligand. However, the mechanism of this transfer is unclear so far. In contrast to the behavior of 1 toward Pd(0) complexes, the reactivity toward Pd(II) complexes was—as expected—more selective. Treatment of the ligand with the Pd(II) precursor [Pd(allyl)Cl]2 selectively gave way to the expected complex [(κP-1)Pd(allyl)Cl], which was isolated in 63% yield as an off-white solid. XRD analysis of the complex confirms the simple coordination of the YPhos ligand via the phosphine donor. As expected for the Pd(II) center no additional coordination of one of the phenyl groups is observed, despite the syn-arrangement of the Pd(allyl) fragment with the PPh3 moiety (Figure ).

Figure 4

Molecular structures of palladium complexes 3 and [(κP-1)Pd(allyl)Cl]. Hydrogen atoms and solvent molecules are omitted for clarity; only one of the two molecules in the asymmetric unit is shown. Displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: 3, P(1)–C(1) 1.7517(13), P(2)–C(1) 1.7516(13), S(1)–C(1) 1.7015(13), Pd(1)–P(1) 2.3374(3), Pd(1)–P(2) 2.3257(3), Pd(1)–P(3) 2.3300(3), Pd(1)–P(4) 2.3236(3), P(1)–Pd(1)–P(2) 71.980(11), S(1)–C(1)–P(1) 126.90(8), P(2)–C(1)–P(1) 102.92(7), S(1)–C(1)–P(2) 129.32(8); [(κP-1)Pd(allyl)Cl, P(1)–C(1) 1.739(4), S(1)–C(1) 1.721(4), C(1)–P(2) 1.782(4), Pd(1)–P(2) 2.3344(11), Cl(1)–Pd(1) 2.3837(11), Pd(1)–C(39A) 2.192(8), Pd(1)–C(40A) 2.149(6), Pd(1)–C(41A) 2.132(9), S(1)–C(1)–P(1) 114.5(2), P(1)–C(1)–P(2) 123.6(2).

The observations made for the group 10 metals led us to further explore the n>an class="Chemical">coordination chemistry of YSPPh2 toward group 9 metals. We particularly focused on precursors in the oxidation state I which might lead to further activation reactions or unique coordination behavior. At first the two frequently used rhodium precursors [Rh(CO)2Cl]2 and [Rh(COD)Cl]2 were tested. Treatment of YSPPh2 with 1 equiv of [Rh(CO)2Cl]2 led to the selective formation of the new complex [(κP,κO-1)Rh(CO)Cl] (Scheme ), which could be isolated as yellow solid in 87% yield (Figure ). The 31P{1H} NMR spectrum of the product features two sets of doublets of doublets due to the coupling of the two phosphorus nuclei with each other and the Rh center. The phosphine signal appears at δP = 37.0 ppm and exhibits the expected large coupling constant of 1JPRh = 142.7 Hz. Diffusion of benzene into a solution of [(κP,κO-1)Rh(CO)Cl] in chloroform gave single crystals suitable for XRD analysis (monoclinic space group P21). In the structure, the YPhos ligand acts as a bidentate ligand coordinating to the rhodium center via the phosphine and the sulfonyl group. Thus, coordination of the phosphine to rhodium is accompanied by the release of one CO ligand. The rhodium atom adopts a square-planar geometry with the chloro ligand in trans-position to the phosphine donor. The CO stretching frequency of ṽ = 1978.6 cm–1 as determined by IR spectroscopy is rather low compared to those reported for other phosphine and even carbene ligands.[14] However, due to the coordination of the sulfonyl group to the rhodium center, no correlation with reported TEP values and thus no direct comparison to other monodentate ligands is possible. However, previous IR measurements of the in situ formed [(κP-YSPPh2)Rh(acac)CO] complex already confirmed the high donor capacity of YSPPh2.[7]

Scheme 2

Preparation of Rhodium Complex [(κP,κO-1)Rh(CO)Cl]

Figure 5

Molecular structure of [(κP,κO-1)Rh(CO)Cl]. Hydrogen atoms are omitted for clarity; displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: C(1)–S(1) 1.700(3), C(1)–P(1) 1.725(3), C(1)–P(2) 1.785(3), Rh(1)–P(2) 2.2013(8), Rh(1)–Cl(1) 2.3666(8), Rh(1)–O(1) 2.105(2), Rh(1)–C(39) 1.779(4), O(3)–C(39) 1.144(4), S(1)–C(1)–P(1) 115.52(17), P(1)–C(1)–P(2) 127.84(17).

Despite the fapan class="Chemical">cile preparation of [(κn>an class="Chemical">P,κO-1)Rh(CO)Cl] the reaction of YSPPh2 with [Rh(COD)Cl]2 was found to be more complex. After mixing of the compounds in THF the formation of two sets of signals with 2:1 intensity was observed by 31P{1H} NMR spectroscopy (Figure ). The minor species 4a showed two doublets of doublets at δP = 20.5 ppm (3JPRh = 6.5 Hz) and δP = 16.9 ppm (1JPRh = 132.6 Hz). These signals clearly argue for the coordination of the YPhos ligand via the phosphine donor, while the phosphonium moiety remains intact. In contrast, the main species 4b showed two doublets of doublets with similar 31P{1H} NMR shifts (δP = 3.7 and 2.8 ppm) and two distinct, large coupling constants between phosphorus and rhodium (1JPRh = 121.8 and 113.8 Hz) and of the two phosphorus atoms with each other (2JPP = 41.8 Hz). These NMR features indicate the cleavage of the P–C bond of one of the phosphonium bound phenyl groups and coordination of the ligand to the metal center via two phosphine moieties as already observed for palladium complex 3 (see above). The slightly different NMR shifts of the two phosphorus atoms probably result from a square planar or octahedral geometry of the complex with slightly different environments.

Figure 6

Extract from the 31P{1H} NMR spectrum of the reaction of YSPPh2 with [Rh(COD)Cl]2.

In order to elupan class="Chemical">cidate the strun>an class="Chemical">cture of the formed compounds, isolation of both species was attempted. However, changing of the reaction conditions (solvent, temperature) always resulted in the same 1:2 ratio between 4a and 4b. While 4a and 4b could be separated from any other impurity and cleanly isolated, all attempts to separate these species by crystallization or chromatography failed. Addition of further coligands (amines, phosphines) resulted in noticeable changes in the NMR spectra, which however were found to be difficult to explain or to correlate with any possible complex structure. Fortunately, under an ammonia atmosphere, single crystals could be obtained, which revealed the formation of the chloro-bridged dimer 5 (Figure ). 5 crystallizes as C-symmetric complex in the triclinic space group P1̅. The molecular structure confirms the P–C bond cleavage and the formation of the anionic bidentate ligand with two PPh2 donor sites, which we already expected from the reaction mixture (Figure ). The rhodium atom adopts an octahedral geometry, in which the phenyl and ammonia ligands are perpendicularly arranged to the plane of the phosphine and chlorido ligands. The P–C distances in the carbanionic ligand of 1.741(2) and 1.740(2) Å are shorter than those found in all other complexes. The central carbon atom features an ideal planar geometry (sum of angles: 359.9(2)°) due to the stabilization of the lone pair via negative hyperconjugation. Complex 5 proofs the proposed P–C activation, which was already expected due to the NMR pattern observed for the reaction of YSPPh2 with [Rh(COD)Cl]2. However, the C symmetry of 5 and that of the thus identical PPh2 moieties disagree with the slightly different shifts observed for the reaction mixture.

Figure 7

Molecular structure of complex 5. Hydrogen atoms and solvent molecules are omitted for clarity. Displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: P(1)–C(1) 1.740(2), P(2)–C(1) 1.741(2), S(1)–C(1) 1.695(2), Rh(1)–P(1) 2.2602(6), Rh(1)–P(2) 2.2600(6), Rh(1)–C(35) 2.026(2), Rh(1)–N(1) 2.2222(17), Rh(1)–Cl(1) 2.4603(5), Rh(1)–Cl(1)′ 2.4657(5), P(1)–C(1)–P(2) 99.20(10), S(1)–C(1)–P(1) 133.18(13), S(1)–C(1)–P(2) 127.54(12).

Sinpan class="Chemical">ce separation of the two spn>en>an class="Chemical">cies seen in the NMR spectra (Figure ) failed, the elucidation of their identity was attempted by their conversion into separable compounds. To this end, AgBF4 was added to a solution of a purified sample of 4a and 4b in CDCl3 for halide abstraction. While the addition of the silver salt led to no distinctive changes in the NMR patterns corresponding to the species 4a, the signals for 4b changed from the observed two doublet of doublets to a single doublet (δP = −15.0 ppm, 1JPRh = 101.7 Hz). The isolation of this new species was unsuccessful but provided a valuable hint to the identity of the unknown compound. Since the observed spectrum upon addition of AgBF4 corroborates with a spectrum of a symmetrical dinuclear rhodium complex, such as compound 5, and since it is presumably produced by chloride abstraction, this suggested that the major species 4b is a dinuclear rhodium complex bridged by three chloride ligands. Because such a complex would be anionic, species 4a must ultimately be a cationic mononuclear rhodium complex. This ultimately explains the constant 2:1 signal intensity and the fact that the two species could not be separated. To support this conclusion, the independent synthesis of both, the cation 4a and anion 4b was attempted (Scheme ). For isolation of cation 4a, 1 was reacted with [Rh(COD)2]BF4, which allowed the isolation of [(κP,κO-1)Rh(COD)]BF4 ([4a][BF4]) in 92% yield. The 31P NMR spectrum of [4a][BF4] exhibits the two doublets at δP = 20.5 and δP = 16.9 ppm, thus corroborating with the signals observed for the reaction mixture of 1 with [Rh(COD)Cl]2 (Figure ). Fortunately, the anionic part 4b of the complex salt could likewise be formed by addition of 0.5 equiv of [PPN]Cl (PPN = bis(triphenylphosphine)iminium) as chloride donor to the reaction of 1 with [Rh(COD)Cl]2, thus giving [PPN][4b] as a yellow solid in 64% yield, which could be fully characterized and unambiguously identified by X-ray crystallography (see below). [PPN][4b] is a dinuclear rhodium(III) complex bridged by three chloride ligands, in which the two coordinating YSPPh2 ligands underwent P–C bond splitting via formal oxidative addition at rhodium. The NMR data of this complex reflected the signals observed in the original product mixture thus confirming the overall formation of the complex salt [4a][4b] from the reaction of 1 with [Rh(COD)Cl]2. The ammonia complex 5 obtained from this complex salt by exposure with NH3 probably results from reaction with the anionic complex [4b]− by replacement of one bridging chloride ligand by two NH3 ligands and formation of [1·Rh(COD)]Cl.

Scheme 3

Reaction of 1 with [Rh(COD)Cl]2

The molepan class="Chemical">cular strun>an class="Chemical">ctures of [4a][BF4] and [PPN][4a] were both determined by X-ray crystallography. Figure only shows the cationic and anionic rhodium complexes, respectively. In the cationic complex, the rhodium atom features a square-planar geometry with the YPhos ligand coordinating via the phosphine and sulfonyl group similar to [(κP,κO-1)Rh(CO)Cl] (Figure ). The Rh–P bond amounts to 2.3052(3) Å and is thus longer than in the neutral complex [(κP,κO-1)Rh(CO)Cl]. The Rh(III) centers in 4b feature a distorted octahedral geometry, with the bridging chlorido ligands adopting one common face of the two octahedra. In contrast to the C symmetric ammonia complex 5, the symmetry in 4b is broken by the additional chlorido ligand. This results in slightly different environments of the two phosphorus atoms in both ligands, which is thus in line with the slightly different shifts observed in the 31P NMR spectrum. Analogous complexes with a Rh(μ-Cl)3Rh unit were reported with other phosphine or cyclopentadienyl ligands.[15] The Rh–Cl bond to the chlorido ligand (2.549(1) and 2.516(1) Å) in trans position to the phenyl ligand is considerable longer than those trans to the phosphine ligand (2.453(1)–2.506(1) Å) due to the different trans effect of both ligands. The P–Rh–P angles are rather acute (72.5(1)°) due to the strained diphosphine bite angle. Also, the Cl–Rh–C angles strongly deviate from the ideal linear geometry.

Figure 8

Molecular structures of (left) [4a][BF4] and (right) [PPN][4b]. Only the rhodium complexes are shown. The corresponding counterions and solvent molecules are omitted for clarity. Displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: [4a][BF4], P(1)–C(1) 1.7457(14), P(2)–C(1) 1.7809(14), S(1)–C(1) 1.7006(14), Rh(1)–P(2) 2.3052(3), Rh(1)–O(1) 2.1129(10), S(1)–C(1)–P(1) 113.79(8), P(1)–C(1)–P(2) 131.16(8), [PPN][4b], P(1)–C(1) 1.771(2), P(2)–C(1) 1.766(2), S(1)–C(1) 1.698(2), Rh(1)–P(1) 2.2518(5), Rh(1)–P(2) 2.2508(5), Rh(1)–C(33) 2.056(2), Rh(1)–Cl(1) 2.5160(5), Rh(1)–Cl(2) 2.5064(5), Rh(1)–Cl(3) 2.4639(5), S(1)–C(1)–P(1) 127.77(14), P(2)–C(1)–P(1) 97.53(11).

To gain further information about the coordination n>an class="Chemical">chemistry of YSPPh2 toward group 9 metals the ligand was treated with half an equivalent of [Ir(COD)Cl]2. In contrast to the rhodium complex, only a single complex was formed, as suggested by NMR spectroscopy, which could be isolated in 78% yield and fully characterized. The complex was identified as complex 6, in which instead of a P–C bond cleavage an ortho-metalation of one phenyl group of the triphenylphosphonium moiety occurred (Scheme ). The complex shows two doublets at δP = 27.5 ppm and δP = −2.9 ppm in the 31P{1H} NMR spectrum (2JPP = 65.7 Hz). The hydride signal appears as a doublet at δH = −15.65 ppm with a coupling constant of 2JHP = 14.4 Hz. Unambiguous confirmation of the ortho-metalation was provided by XRD analysis. Single crystals were obtained by diffusion of n-hexane into a solution of 6 in THF. The complex crystallizes in the triclinic space group P1̅ with two molecules in the asymmetric unit. The hydrido ligand in the complex was directly found in the difference Fourier map and refined independently. In the structure, the iridium center adopts an octahedral geometry (Figure ). Due to the orthometalation, YPPh acts as monoanionic bidentate ligand, coordinating to the metal via the phosphine and aryl moiety. The phosphine and the COD ligand are trans to each other. The Ir–P bond lengths of 2.334(1) and 2.313(1) Å are in the range of reported Ir(III)–P distances.[16] The P1–C1 distance to the phosphonium moiety of 1.743(4) Å is slightly shorter than the one found to the phosphine group (1.779(4) Å), albeit the difference is less pronounced than in the free ligand 1.[7]

Scheme 4

Formation of 6 via Cyclometalation

Figure 9

Molecular structure of complex 6•. Hydrogen atoms and solvent molecules are omitted for clarity; only one of the two molecules in the asymmetric unit is shown. Displacement parameters at the 50% level. Selected bond lengths [Å] and angles [deg]: Ir(1)–C(10) 2.066(3), Ir(1)–Cl(1) 2.4711(10), Ir(1)–P(2) 2.3335(9), Ir(1)–H(1) 1.46(4) P(1)–C(1) 1.743(4), S(1)–C(1) 1.726(4), P(2)–C(1) 1.779(4)

Conclusions

In pan class="Chemical">conn>an class="Chemical">clusion, we reported a detailed investigation of the coordination chemistry of the ylide-functionalized phosphine YSPPh2 toward group 9 and 10 metals using metal precursors often used in transition metal catalysis. The formed complexes demonstrate on the one hand the strong donor properties of the ligand and on the other hand its diverse coordination chemistry. As such, the ligand can act as neutral mono and bidentate ligand binding via the phosphine and sulfonyl group to the metal center. In case of low-valent metal centers (Ni(0), Pd(0), Rh(I), and Ir(I)) bond activation reactions in the ligand can be observed. This results in either a cleavage (Pd, Rh) or a weakening (Ni) of the P–C bond to one of the phenyl groups of the phosphonium moiety or in an ortho-metalation reaction (Ir). Overall, these findings provide valuable insights into the coordination chemistry of YPhos ligands and give important information for further improvements of the ligand design. The latter will be important for further applications of these ligands in catalysis.

Experimental Section

General Procedures

All manipulations were performed under a dry, pan class="Chemical">oxygen-free n>an class="Chemical">argon atmosphere in dried Schlenk-type glassware or in an argon-filled glovebox. Involved solvents were dried using an MBraun SPS-800 (THF, Toluene, Et2O, DCM, Pentane, Hexane) or dried in accordance with standard procedures. 1H, 13C{1H}, 31P{1H} NMR spectra were recorded on Avance I 500 or Avance III 400 spectrometers at 25 °C if not stated otherwise. 1H and 13C{1H} chemical shifts were referenced to the residual 1H and 13C resonances of the deuterated solvents and are reported relative to TMS. 31P{1H} resonances were referenced to external 85% phosphoric acid. All values of the chemical shift are in ppm regarding the δ-scale. All spin–spin coupling constants (J) are printed in hertz (Hz). To display multiplicities and signal forms correctly the following abbreviations were used: s = singlet, d = doublet, t = triplet, m = multiplet, dd = doublet of doublet, dt = doublet of triplet, and br = broad signal. Signal assignment was supported by DEPT, APT, HSQC and HMBC experiments. Elemental analyses were performed on an Elementar vario MICRO cube elemental analyzer. 1,[17]2,[7]2·Ni(CO)3,[7] [Rh(COD)Cl]2,[18] Rh(COD)2BF4,[19] and Ni(CO)4[20] were prepared according to published procedures. All other reagents were purchased from Sigma-Aldrich, ABCR, Rockwood Lithium, or Acros Organics and used without further purification.

Synthesis of [1·Ni(CO)2]

1 (400 mg, 0.65 mmol) was dissolved in 20 mL of pan class="Chemical">benzene and a 0.6 M solution of n>an class="Chemical">Ni(CO)4 in benzene (1.6 mL, 0.98 mmol) was added dropwise. For 6 h, the solution was stirred and argon was bubbled through it slowly to remove CO. The solvent was reduced to about 3 mL under vacuum and filtered and then 6 mL of pentane were added, upon which a solid precipitated. The solid was filtered off, and dried under vacuum, The solid was dissolved in 20 mL of a hot 1:1 mixture of toluene and cyclohexane and the stored at 5 °C for several days, upon red crystals of 1·Ni(CO)2 formed. The crystals were removed from the supernatants and dried, affording crude 1·Ni(CO)2 (purity was 85%, according to 31P{1H} NMR) as a red-orange solid. (110 mg, 0.15 mmol, 23%). Single crystals of 1·Ni(CO)2 suitable for X-ray crystallography were obtained by slow diffusion of pentane into a solution of 1·Ni(CO)2 in Benzene. Single crystals of 1·Ni(CO)3 suitable for X-ray crystallography were instead obtained by slow diffusion of pentane into a solution of 1·Ni(CO)2 in DCM under an atmosphere of CO. 1H NMR (400.3 MHz, CD2Cl2, −30 °C): δ = 1.83 (s, 3H; CH3), 6.42–6.54 (m, 4H; CHTol), 6.80–7.18 (m, 20H; CHPPh), 7.20–7.27 (m, 4H; CHPPh), 7.43–7.52 (m, 6H; CHPPh), 8.32–8.41 (m, 29H; CHPPh). 31P{1H} NMR (162.1 MHz, CD2Cl2, −30 °C): δ = 24.8.

Isolation of Crystals of 3

1 (20 mg, 32.5 μmol) and Pd(dba)2 (19 mg, 33.0 mmol) were dissolved in 0.6 mL of THF-d8. The solution was heated to 60 °C for 16 h and then filtered. Slow evaporation of the solution lead to the formation of orange crystals of 3, suitable for X-ray crystallography.

Synthesis of [(κP-1)Pd(allyl)Cl]

1 (201 mg, 0.325 mmol) and [pan class="Chemical">Pdn>an class="Chemical">Cl(η3-C3H5)]2 (59 mg, 0.163 mmol) were dissolved in 10 mL of DCM and stirred for 1 h. The solvent was reduced to about 5 mL under vacuum, and then 10 mL of pentane was added, upon which a solid precipitated. The solid was filtered off, washed with 5 mL of pentane, and dried under vacuum, affording 1·Pd(allyl)Cl as an off-white solid (163 mg, 0.21 mmol, 63%). Single crystals suitable for X-ray crystallography were obtained by slow diffusion of pentane into a solution of 1·Pd(allyl)Cl in DCM. 1H NMR (500.1 MHz, CD2Cl2): δ = 1.8–2.5 (br, 2H; CH2, allyl), 2.22 (s, 3H; CH3), 2.76 (br, 1H; CH2, allyl), 4.12 (m, 1H; CH2, allyl), 4.84 (br, 1H; CHallyl), 6.71–6.73 (m, 2H; CHTol, meta), 6.76–6.78 (m, 2H; CHTol, ortho), 7.16–7.18 (m, 4H; CHPdPPh, meta), 7.22–7.25 (m, 2H; CHPdPPh, para), 7.41–7.45 (m, 6 H; CHPPh, meta), 7.53–7.57 (m, 3H; CHPPh, para), 7.84–7.88 (m, 4H; CHPdPPh, ortho), 7.97–8.01 (m, 6H; CHPPh, ortho). 13C{1H} NMR (125.8 MHz, CD2Cl2): δ = 21.3 (CH3), 42.3 (dd, 1JCP = 105.2 Hz, 1JCP = 20.4 Hz; CPCS), 64.7 (br; CH2, allyl), 78.3 (d, 2JCP = 31.8 Hz; CH2, allyl), 117.7 (d, 2JCP = 4.3 Hz; CHallyl), 126.5 (CHTol, ortho), 127.4 (d, 2JCP = 10.3 Hz; CHPdPPh, meta), 128.3 (dd, 1JCP = 94.0 Hz, 3JCP = 1.2 Hz; CPPh, ipso), 128.4 (dd, 1JCP = 55.1 Hz, 3JCP = 12.4 Hz; CHPdPPh, ipso), 128.5 (CHTol, meta), 128.5 (d, 3JCP = 12.8 Hz; CHPPh, meta), 129.4 (d, 4JCP = 2.0 Hz; CHPdPPh, para), 132.3 (d, 4JCP = 3.0 Hz; CHPPh, para), 135.2 (d, 2JCP = 10.5 Hz; CHPdPPh, ortho), 136.2 (d, 2JCP = 10.1 Hz; CHPPh, ortho), 140.9 (CTol, para), 144.2 (CTol, ipso). 31P{1H} NMR (162.0 MHz, CD2Cl2): δ = 9.9 (d, 2JPP = 67.3 Hz), 22.9 (d, 2JPP = 67.3 Hz). Anal. Calcd for C41H37O2P2SClPd: C, 61.74; H 4.68; S, 4.02. Found: C, 61.47; H 4.69; S, 3.72

Synthesis of [(κP,κO-1)Rh(CO)Cl]

1 (500 mg, 0.81 mmol) and pan class="Chemical">[Rh(CO)2Cl]2 (158 mg, 0.41 mmol) were dissolved in 15 mL of n>an class="Chemical">DCM, which resulted in vigorous gas evolution. The solution was stirred for 30 min, and was filtered to remove a small amount of insoluble material. Under stirring, 15 mL of pentane was added, which resulted in the formation of a yellow precipitate. The solid was filtered off, washed twice with 5 mL of pentane and dried under vacuum, affording 1·Rh(CO)Cl as a yellow solid (553 mg, 0.71 mmol, 87%). Single crystals suitable for X-ray crystallography were obtained by slow diffusion of benzene into a solution of 1·Rh(CO)Cl in chloroform. 1H NMR (500.1 MHz, CD2Cl2): δ = 2.38 (s, 3H; CH3), 6.92–6.98 (m, 2H; CHRhPPh, meta), 6.99–7.03 (m, 2H; CHTol, meta), 7.11–7.16 (m, 1H; CHRhPPh, para), 7.22–7.25 (m, 2H; CHTol, ortho), 7.32–7.43 (m, 12H; CHPPh, ortho+RhPPh, ortho+RhPPh, meta), 7.43–7.54 (m, 7H; CHPPh, ortho+RhPPh, para), 7.57–7.62 (m, 3H; CHPPh, para). 13C{1H} NMR (125.8 MHz, CD2Cl2): δ = 21.6 (CH3), 41.6 (dd, 1JCP = 91.4 Hz, 1JCP = 33.8 Hz; CPCS), 122.8 (d, 1JCP = 92.6 Hz; CPPh, ipso), 126.7 (CHTol, ortho), 128.1 (d, 3JCP = 11.9 Hz; CHRhPPh, meta), 128.7 (d, 3JCP = 11.3 Hz; CHRhPPh, meta), 129.1 (d, 3JCP = 12.7 Hz; CPPh, meta), 129.4 (CHTol, meta), 130.4 (d, 4JCP = 2.5 Hz; CHRhPPh, para), 130.5 (d, 4JCP = 2.5 Hz; CHRhPPh, para), 131.9 (d, 2JCP = 12.3 Hz; CHRhPPh, ortho), 132.2 (d, 1JCP = 58.0 Hz; CRhPPh, ipso), 133.6 (d, 4JCP = 2.9 Hz; CHPPh, para), 133.9 (d, 1JCP = 58.3 Hz; CRhPPh, ipso), 135.0 (d, 2JCP = 14.0 Hz; CHRhPPh, ortho), 135.4 (d, 2JCP = 10.3 Hz; CHPPh, ortho), 142.0 (CTol, para), 143.4 (CHTol, ipso), 188.0 (dd, 1JCRh = 85.1 Hz, 2JCP = 15.6 Hz; CRhCO). 31P{1H} NMR (202.5 MHz, CD2Cl2): δ = 19.3 (dd, 2JPP = 9.5 Hz, 3JPRh = 7.8 Hz), 37.0 (dd, 1JPRh = 142.7 Hz, 2JPP = 9.5 Hz). Anal. Calcd for C39H32O3P2SClRh: C, 59.97; H 4.13; S, 4.10. Found: C, 59.93; H 4.12; S, 3.89.

Synthesis of [4a][BF4]

1 (306 mg, 0.50 mmol) and pan class="Chemical">Rh(COD)2BF4 (200 mg, 0.50 mmol) were dissolved in 3 mL of n>an class="Chemical">THF and stirred for 1 h, during which a yellow solid precipitated. To the mixture was added 2 mL of Et2O, and the mixture was stirred for another 30 min. The solid was filtered off and washed twice with 2 mL of Et2O and dried under vacuum, affording [4a][BF4] as a yellow solid (410 mg, 0.45 mmol, 92%). NMR spectra of this compound were recorded at −30 °C, since some signals were very broad at room temperature. Single crystals suitable for X-ray crystallography were obtained by slow diffusion of hexane into a solution of [4a][BF4] in chloroform. 1H NMR (400.3 MHz, CD2Cl2, −30 °C): δ = 1.69–1.83 (m, 1H; CH2,COD), 1.83–1.98 (m, 1H; CH2,COD), 1.98–2.12 (m, 1H; CH2,COD), 2.12–2.39 (m, 3H; CH2,COD), 2.39–2.60 (m, 2H; CH2,COD), 2.47 (s, 3H; CH3), 2.71–2.83 (m, 1H; CHCOD), 3.17–3.28 (m, 1H; CHCOD), 5.18–5.31 (m, 1H; CHCOD), 5.44–5.55 (m, 1H; CHCOD), 7.10–7.66 (m, 29H; CH). 13C{1H} NMR (100.7 MHz, CD2Cl2, −30 °C): δ = 21.5 (CH3), 26.4 (CH2,COD), 29.5 (CH2,COD), 30.5 (CH2,COD), 34.0 (CH2,COD), 40.0 (dd, 1JCP = 88.8 Hz, 1JCP = 33.8 Hz; CPCS), 71.7 (d, 1JCRh = 14.5 Hz; CHCOD), 74.7 (d, 1JCRh = 15.4 Hz; CHCOD), 104.3 (dd, 1JCRh = 10.5 Hz, 2JCP = 7.0 Hz; CHCOD), 104.3 (dd, 1JCRh = 10.7 Hz, 2JCP = 6.9 Hz; CHCOD), 120.6 (d, 1JCP = 92.8 Hz; CPPh, ipso), 125.5 (CHTol, ortho), 128.5 (d, 3JCP = 11.5 Hz; CHRhPPh, meta), 128.6 (d, 1JCP = 58.0 Hz; CRhPPh, ipso), 128.7 (d, 3JCP = 12.6 Hz; CPPh, meta), 129.0 (d, 3JCP = 10.8 Hz; CHRhPPh, meta), 129.3 (d, 1JCP = 53.3 Hz; CRhPPh, ipso), 129.5 (CHTol, meta), 130.1 (d, 2JCP = 11.0 Hz; CHRhPPh, ortho), 130.7 (CHRhPPh, para), 131.3 (CHRhPPh, para), 133.6 (d, 4JCP = 2.2 Hz; CHPPh, para), 134.7 (d, 2JCP = 14.1 Hz; CHRhPPh, ortho), 134.8 (d, 2JCP = 9.7 Hz; CHPPh, ortho), 141.0 (CTol, para), 143.8 (CHTol, ipso). 31P{1H} NMR (162.1 MHz, CD2Cl2, −30 °C): δ = 16.6 (dd, 1JPRh = 132.2 Hz, 2JPP = 13.1 Hz), 20.0 (dd, 2JPP = 13.1 Hz, 3JPRh = 7.3 Hz). Anal. Calcd for C46H44BO2F4P2SRh: C, 60.54; H 4.86; S, 3.51. Found: C, 60.55; H 5.09; S, 3.30.

Synthesis of [PPN][4b]

1 (600 mg, 0.98 mmol), pan class="Chemical">[Rh(COD)Cl]2 (240 mg, 0.49 mmol), and n>an class="Chemical">[PPN]Cl (280 mg, 49 mmol) were dissolved in 30 mL of THF and heated to 55 °C for 3 days, during which a solid precipitated. The solid was filtered off and washed with 10 mL of THF and dried under vacuum. The solid was dissolved in 12 mL of DCM, filtered to remove a small amount of insoluble material, and then precipitated by addition of 12 mL of Et2O. The solid was filtered off and washed twice with 5 mL of Et2O and dried under vacuum, affording [PPN][4b] as a yellow solid (795 mg, 0.38 mmol, 64%). Single crystals suitable for X-ray crystallography were obtained by evaporation of a solution of [PPN][4b] in a 1:1 DCM:benzene mixture. 1H NMR (400.3 MHz, CD2Cl2): δ = 2.20 (s, 6H; CH3), 6.00–6.09 (m, 4H; CHRhPh, meta), 6.34–6.42 (m, 2H; CHRhPh, para), 6.72–6.79 (m, 4H; CHPPh,meta), 6.81–6.86 (m, 4H; CHTol, ortho), 6.87–6.94 (m, 4H; CHPPh,meta), 6.94–6.99 (m, 2H; CHPPh,para,), 7.05–7.11 (m, 2H; CHPPh,para,), 7.13–7.23 (m, 10H; CHRhPh,ortho + CHPPh,meta + CHPPh,para,), 7.32–7.38 (m, 4H; CHTol, meta), 7.38–7.55 (m, 34H; CHPPN,ortho + CHPPN,meta + CHPPh,ortho + CHPPh,meta + CHPPh,para,), 7.62–7.68 (m, 6H; CHPPN,para,), 7.71–7.79 (m, 4H; CHPPh,ortho), 7.79–7.86 (m, 4H; CHPPh,ortho), 8.15–8.23 (m, 4H; CHPPh,ortho). 13C{1H} NMR (100.7 MHz, CD2Cl2): δ = 21.3 (CH3), 50.6 (dt, 1JCP = 42.0 Hz, 1JCP = 33.8 Hz; CPCS), 121.8 (CHRhPh, para), 124.4 (CHRhPh, meta), 126.6 (d, 2JCP = 11.3 Hz; CHPPh, ortho), 126.7 (d, 2JCP = 11.4 Hz; CHPPh, ortho), 126.8 (CHTol, ortho), 127.1 (d, 2JCP = 12.1 Hz; CHPPh, ortho), 127.3 (d, 2JCP = 11.9 Hz; CHPPh, ortho), 127.4 (dd, 1JCP = 108.0 Hz, 3JCP = 1.9 Hz; CHPPN,ipso), 128.6 (CHTol, meta), 128.8 (d, 4JCP = 2.8 Hz; CHPPh, para), 129.2 (d, 4JCP = 2.2 Hz; CHPPh, para), 129.3 (d, 4JCP = 3.0 Hz; CHPPh, para), 129.5 (d, 4JCP = 2.2 Hz; CHPPh, para), 129.8–130.0 (m; CHPPN,ortho), 132.4–132.6 (m; CHPPN,meta), 133.2 (dd, 1JCP = 55.5 Hz, 3JCP = 3.0 Hz; CPPh, ipso), 133.3 (dd, 1JCP = 56.5 Hz, 3JCP = 2.9 Hz; CPPh, ipso), 134.1 (d, 3JCP = 10.8 Hz; CHPPh, meta), 134.2 (CHPPN, para), 134.3 (d, 3JCP = 10.5 Hz; CHPPh, meta), 135.7 (d, 3JCP = 10.2 Hz; CHPPh, meta), 136.5 (d, 3JCP = 9.8 Hz; CHPPh, meta), 137.3 (d, 1JCP = 59.4 Hz; CPPh, ipso), 138.6 (d, 1JCP = 59.1 Hz; CPPh, ipso), 141.0 (CTol, para), 141.9 (CHRhPh, ortho), 143.8 (CHTol, ipso), 146.5 (dt, 1JCRh = 30.8 Hz, 2JCP = 8.6 Hz CHRhPh, ipso). 31P{1H} NMR (162.1 MHz, CD2Cl2): δ = 21.0, 3.4 (dd, 1JPRh = 121.2 Hz, 2JPP = 41.0 Hz), 2.2 (dd, 1JPRh = 113.3 Hz, 2JPP = 41.0 Hz). Anal. Calcd for C112H94NO4P6S2Rh2: C, 64.67; H 4.56; N, 0.67; S, 3.08. Found: C, 64.69; H 4.54; N, 0.77; S, 2.93.

Synthesis of [4a][4b]

1 (500 mg, 0.81 mmol) and pan class="Chemical">[Rh(COD)Cl]2 (200 mg, 0.41 mmol dissolved in 20 mL of n>an class="Chemical">THF and heated to 55 °C for 3 days. The solvent was removed under vacuum and the residue was subjected to column chromatography (SiO2), with a gradient from 50% Ethyl acetate in DCM to 95% ethyl acetate in DCM, affording [4a][4b] as a pale orange solid (283 mg, 0.12 mmol, 44%). Some signals in the 13C{1H} NMR spectra for the cationic part (4a) are very broad at room temperature and could not be assigned; see synthesis of [4a][BF4]. Single crystals of 5 suitable for X-ray crystallography were obtained by storing a solution of [4a][4b] in chloroform under an atmosphere of ammonia for several days. 1H NMR (400.3 MHz, CD2Cl2): δ = 1.87–2.55 (m, 8H; CH2,COD, a), 2.20 (s, 6H; CH3, b), 2.49 (s, 3H; CH3, a), 2.88–3.24 (m, 2H; CHCOD), 5.26–5.50 (m, 2H; CHCOD), 6.00–6.09 (m, 4H; CHRhPh, meta, b), 6.34–6.42 (m, 2H; CHRhPh, para, b), 6.72–6.79 (m, 4H; CHPPh,meta, b), 6.81–6.86 (m, 4H; CHTol, ortho, b), 6.87–6.94 (m, 4H; CHPPh,meta, b), 6.94–6.99 (m, 2H; CHPPh,para, b), 7.05–7.11 (m, 2H; CHPPh,para, b), 7.13–7.26 (m, 12H; CHRhPh,ortho, b + CHPPh,meta, b + CHPPh,para, b+ CHTol,ortho, a), 7.27–7.61 (m, 39H; CHPPh,ortho, b + CHPPh,meta, b + CHPPh,para, b + CHTol, meta, b + CHPPh, a+ CHRhPPh, a), 7.68–7.79 (m, 6H; CHPPh, ortho, b + CHTol,meta, a), 7.79–7.86 (m, 4H; CHPPh,ortho, b), 8.15–8.23 (m, 4H; CHPPh,ortho, b). 13C{1H} NMR (100.7 MHz, CD2Cl2): δ = 21.3 (CH3, b), 21.8 (CH3, a), 28.5 (br, CH2,COD, a), 32.7 (br, CH2,COD, a), 41.1 (dd, 1JCP = 88.3 Hz, 1JCP = 33.8 Hz; CPCS, a), 50.6 (dt, 1JCP = 42.0 Hz, 1JCP = 33.8 Hz; CPCS, b), 73.5 (br; CHCOD, a), 105.2 (br; CHCOD, a), 121.6 (d, 1JCP = 92.2 Hz; CPPh, ipso, a), 121.8 (CHRhPh, para, b), 124.4 (CHRhPh, meta, b), 126.2 (CHTol, ortho, a), 126.6 (d, 2JCP = 11.3 Hz; CHPPh, ortho, b), 126.7 (d, 2JCP = 11.4 Hz; CHPPh, ortho, b), 126.8 (CHTol, ortho, b), 127.1 (d, 2JCP = 12.1 Hz; CHPPh, ortho, b), 127.3 (d, 2JCP = 11.9 Hz; CHPPh, ortho, b), 128.6 (CHTol, meta, b), 128.8 (d, 4JCP = 2.8 Hz; CHPPh, para, b), 129.17 (d, 4JCP = 2.2 Hz; CHPPh, para, b), 129.19 (d, 3JCP = 13.0 Hz; CPPh, meta, a), 129.3 (d, 4JCP = 3.0 Hz; CHPPh, para, b), 129.5 (d, 4JCP = 2.2 Hz; CHPPh, para, b), 129.9 (CHTol, meta, a), 131.5 (CHRhPPh, para, a), 133.2 (dd, 1JCP = 55.5 Hz, 3JCP = 3.0 Hz; CPPh, ipso, b), 133.3 (dd, 1JCP = 56.5 Hz, 3JCP = 2.9 Hz; CPPh, ipso, b), 134.0 (d, 4JCP = 3.0 Hz; CHPPh, para, a), 134.1 (d, 3JCP = 10.8 Hz; CHPPh, meta, b), 134.3 (d, 3JCP = 10.5 Hz; CHPPh, meta, b), 135.3 (d, 2JCP = 10.5 Hz; CHPPh, ortho, a), 135.7 (d, 3JCP = 10.2 Hz; CHPPh, meta, b), 136.5 (d, 3JCP = 9.8 Hz; CHPPh, meta, b), 137.3 (d, 1JCP = 59.4 Hz; CPPh, ipso, b), 138.6 (d, 1JCP = 59.1 Hz; CPPh, ipso, b), 141.0 (CTol, para, b), 141.9 (CHRhPh, ortho, b), 142.0 (CTol, para, a), 143.8 (CHTol, ipso, b), 144.3 (CHTol, ipso, a), 146.5 (dt, 1JCRh = 30.8 Hz, 2JCP = 8.6 Hz CHRhPh, ipso, b). 31P{1H} NMR (162.1 MHz, CD2Cl2): δ = 3.4 (dd, 1JPRh = 122.1 Hz, 2JPP = 41.8 Hz), 2.2 (dd, 1JPRh = 113.6 Hz, 2JPP = 41.8 Hz), 16.6 (dd, 1JPRh = 132.3 Hz, 2JPP = 13.6 Hz), 20.0 (dd, 2JPP = 13.6 Hz, 3JPRh = 7.6 Hz). Anal. Calcd for C122H108O6P6S3Cl3Rh3: C, 61.90; H 4.60; S, 4.06. Found: C, 61.68; H 4.60; S, 3.99.

Synthesis of 6

One (400 mg, 0.65 mmol) and [Ir(COD)n>an class="Chemical">Cl]2 (220 mg, 0.33 mmol) were dissolved in 20 mL of benzene and stirred for 3 days. The solution was filtered and the remaining solids washed with 2 mL of benzene. The solution was reduced to 10 mL under vacuum, and then 10 mL of pentane was added, which caused precipitation of a solid. The solid was filtered off and washed twice with 5 mL of pentane and dried under vacuum, affording 6 as an off-white solid (486 mg, 0.51 mmol, 78%). NMR spectra of this compound were recorded at −30 °C, since some signals were very broad at room temperature. Single crystals suitable for X-ray crystallography were obtained by slow diffusion of hexane into a solution of 6 in THF. 1H NMR (400.3 MHz, CD2Cl2, −30 °C): δ = −15.65 (d, 2JHP = 14.4 Hz; HIr) 0.47–0.62 (m, 1H; CH2,COD), 1.05–1.19 (m, 1H; CH2,COD), 1.38–1.51 (m, 1H; CH2,COD), 1.83–2.01 (m, 2H; CH2,COD), 2.01–2.14 (m, 1H; CH2,COD), 2.13 (s, 3H; CH3), 2.60–2.84 (m, 2H; CH2,COD), 3.23–3.34 (m, 1H; CHCOD), 3.51–3.61 (m, 1H; CHCOD), 3.84–3.94 (m, 1H; CHCOD), 4.21–4.32 (m, 1H; CHCOD), 5.47–5.62 (m, 2H; CHTol, ortho), 6.20–6.36 (m, 2H; CHPPh), 6.38–6.48 (m, 2H; CHTol, meta), 6.83–6.99 (m, 3H; CHPPh), 7.15–7.71 (m, 14H; CHPPh), 7.72–7.81 (m, 1H; CHPPh), 7.94–8.01 (m, 1H; CHPPh), 8.30–8.37 (m, 1H; CHPPh), 8.45–8.57 (m, 1H; CHPPh), 9.34–9.43 (m, 1H; CHPPh). 13C{1H} NMR (100.7 MHz, CD2Cl2, −30 °C): δ = 20.9 (CH3), 28.0 (CH2,COD), 28.8 (CH2,COD), 29.0 (d, 3JCP = 2.9 Hz CH2,COD), 33.0 (CH2,COD), 41.5 (dd, 1JCP = 111.1 Hz, 1JCP = 58.3 Hz; CPCS), 93.2 (d, 2JCP = 9.3 Hz; CHCOD), 95.2 (CHCOD), 97.7 (CHCOD), 98.6 (d, 2JCP = 17.6 Hz; CHCOD), 121.5 (d, JCP = 13.4 Hz; CHPPh), 121.8 (dd, 1JCP = 88.2 Hz, 3JCP = 8.0 Hz; CPPh), 124.3 (CHTol, ortho), 125.4 (d, JCP = 11.6 Hz; CHPPh), 126.1 (d, JCP = 12.5 Hz; CHPPh), 126.5 (d, JCP = 8.5 Hz; CHPPh), 127.1 (d, JCP = 11.1 Hz; CHPPh), 127.7 (d, JCP = 12.0 Hz; CHPPh), 128.3 (CHTol, meta), 129.0 (d, JCP = 1.5 Hz; CHPPh), 129.4 (d, JCP = 13.0 Hz; CHPPh), 129.7 (d, JCP = 2.5 Hz; CHPPh), 129.9 (d, JCP = 12.6 Hz; CHPPh), 130.2 (d, 1JCP = 86.6 Hz; CPPh), 130.9 (d, JCP = 2.7 Hz; CHPPh), 131.1 (d, JCP = 12.5 Hz; CHPPh), 131.6 (d, JCP = 3.7 Hz; CHPPh), 131.9 (d, JCP = 14.0 Hz; CHPPh), 132.4 (d, JCP = 2.6 Hz; CHPPh), 132.6 (dd, 1JCP = 65.3 Hz, 3JCP = 2.2 Hz; CPPh), 133.2 (d, JCP = 6.6 Hz; CHPPh), 133.6 (d, JCP = 9.8 Hz; CHPPh), 133.8 (d, JCP = 16.9 Hz; CHPPh), 134.2 (dd, 1JCP = 95.4 Hz, 3JCP = 2.9 Hz; CPPh), 134.5 (dd, 1JCP = 74.8 Hz, 3JCP = 3.1 Hz; CPPh), 134.9–135.4 (br; CHPPh), 135.3 (d, JCP = 8.4 Hz; CHPPh), 137.3 (d, JCP = 10.1 Hz; CHPPh), 138.7 (d, JCP = 15.4 Hz; CHPPh), 140.2 (CTol, para), 145.5 (CHTol, ipso), 146.6 (dd, 2JCP = 19.1 Hz, 2JCP = 10.1 Hz; CIr). 31P{1H} NMR (162.1 MHz, CD2Cl2, −30 °C): δ = −2.9 (d, 2JPP = 65.7 Hz), 27.5 (d, 2JPP = 65.7 Hz). Anal. Calcd for C46H44O2P2SClIr: C, 58.13; H 4.67; S, 3.37. Found: C, 58.38; H 4.64; S, 3.03

X-ray Crystallographic Studies

Data collen>an class="Chemical">ction of all compounds was conducted either with a Bruker X8-APEX II (1·Ni(CO)3, 1·Ni(CO)2, 1·Pd(allyl)Cl, 1·Rh(CO)Cl, 5) or a Rigaku XtaLAB Synergy (1, 3, [4a][BF4], [PPN][4b], 6). Suitable crystals of all compounds were mounted in an inert oil (perfluoropoly alkylether) and directly transferred into a cold nitrogen stream. Crystal structure determinations were affected at 100 K. The structures were solved using direct methods, refined using full-matrix least-squares techniques on F2 with the Shelx software package[21] and expanded using Fourier techniques. Data collection parameters are given in Tables S1–S4. Crystallographic data (including structure factors) have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-1906068–1906077.