Sequential Electrophilic Substitution Reactions of Tungsten-Coordinated Phosphenium Ions and Phosphine Triflates.

ion of chloride from [W(CO)5{PPhCl2}] with AgOSO2CF3 leads to the phosphine triflate complex [W(CO)5{PPhCl(OSO2CF3)}] which undergoes electrophilic substitution reactions with N,N-diethylaniline, anisole, N,N-dimethyl-p-toluidine, toluene, biphenyl, naphthalene, 2,7,9,9-tetramethyl xanthene, and allyltrimethylsilane to form the chlorophosphine complexes [W(CO)5{PPhClR}], where R = p-diethylanilinyl, p-anisyl, 2-(N,N-dimethyl-4-methylphenyl), p-tolyl, p-phenylphenyl, 1-naphthyl, 4-(2,7,9,9-tetramethylxanthyl), and allyl. Abstraction of the second chloride with AgOSO2CF3 leads, in most cases, to the respective phosphine triflates [W(CO)5{PPhR(OSO2CF3)}], which react with ferrocene to form the ferrocenyl phosphine complexes [W(CO)5{PPhR(C10H9Fe)}]. The W(CO)5 unit can be removed via photolysis in the presence of bis(diphenylphosphino)ethane to form metal-free phosphines.

Introduction

Phosphines containing three different substituents are of interest because they are stereogenic at P and therefore chiral.[1] Because barriers to inversion at P are high,[2] chiral phosphines retain their stereochemistry, and chiral nonracemic phosphines can be isolated and used as ligands for asymmetric catalysis[3] and used directly for organic catalysis.[4] The synthesis of heteroleptic phosphines from simple starting materials such as chlorophosphines typically requires a strategy to control the degree of substitution.[5] This can be done by using weak nucleophiles such as mercury or lead alkyls, which selectively substitute a single chloride,[6] or through the use of leaving groups of varying ability[7] or protection–deprotection strategies.[8] In many cases, controlled monosubstitution can be achieved with Grignard or lithium reagents, particularly when adding large groups.[9] However, all of these strategies rely on organometallic nucleophiles, limiting potential substrates and limiting functional group tolerance.[5b] It would be advantageous to be able to use milder nucleophiles to form P–C bonds in a controlled, sequential fashion to form P-stereogenic phosphines, widening the range of potential substrates. One method that can be used to enhance P electrophilicity is chloride abstraction from chlorophosphines to form phosphenium ions, which then react with milder organic nucleophiles such as aromatic compounds.[10] Although this methodology has been known for a long time, it is not widely applied. We reasoned that the electrophilicity of phosphenium ion intermediates might be enhanced by coordinating them to an electron-poor transition-metal complex.[11] Metal-coordinated phosphenium ions have been studied extensively,[12] but prior to our work, little work had been done on their applications toward P–C bond formation.[12a,13] By contrast, activation of C–H and C–X bonds by metal-coordinated phosphinidenes to form phosphines is well-established.[14]

We have shown that by coordinating a chlorophosphine to a W(CO)5 complex and then extracting chloride with AlCl3 or AgOSO2CF3, we can generate highly electrophilic phosphenium ions or phosphine triflates that react with a wide range of organic substrates, including arenes, heteroarenes, alkenes, and alkynes (Scheme ).[15] The purpose of this study is to apply this methodology sequentially to form phosphines with three different substituents, using dichlorophenylphosphine as a starting point. Portions of this work have been communicated.[16]

Scheme 1

Results and Discussion

The precursor n>an class="Chemical">complex [W(CO)5{PPhCl2}] (1) is easily synthesized from W(CO)6 and PPhCl2.[17] Reaction of 1 with AlCl3 in CH2Cl2 led to a solution with no observable 31P signals, suggesting that an equilibrium mixture of 1 with the phosphenium ion complex [W(CO)5{PPhCl}][AlCl4] is formed and that the dynamic exchange is leading to the broadening of the signal. At temperatures below −10 °C, the signal resolves into a peak at δ 128.7, which corresponds to the chemical shift for 1. No downfield peak that can be assigned as the phosphenium ion complex was observed. This suggests that the equilibrium lies far toward the starting chlorophosphine (Scheme ). However, the reactivity of this solution clearly shows that the phosphenium ion is formed. A similar equilibrium between the chlorophosphine complex and the phosphenium complex was observed when chloride was abstracted from [W(CO)5{PPh2Cl}].[15]

Scheme 2

Reaction of the 1/AlCl3 mixture with 1 equiv of N,N-diethylaniline resulted in electrophilic aromatic substitution, leading to the bis-para-anilinyl phenyl phosphine complex 2, along with unreacted 1, in a 1:1 ratio.[16] Compound 1 does not react with N,N-diethylaniline in the absence of AlCl3. This reaction is strong evidence for the formation of the phosphenium ion complex, even though it could not be directly observed. No evidence for a monosubstituted product was observed. Complete conversion to disubstituted product 2 can be achieved by using 3 equiv of AlCl3 and 2 equiv of N,N-diethylaniline (Scheme ). Excess AlCl3 is used because it increases the proportion of the phosphenium ion complex generated in the equilibrium shown in Scheme , thus increasing the reaction rate. The hydrochloric acid generated likely protonates the amine groups in the reaction mixtures but is scavenged by silica gel during chromatography, allowing the isolation of the neutral product. The lack of monosubstitution can be rationalized by considering the relative stabilities of the phosphenium intermediates involved. The first substitution involves a chloro-phenyl phosphenium intermediate, which is destabilized by the electron-withdrawing chloro substituent. The second substitution involves an anilinyl-phenyl phosphenium intermediate, which is stabilized by the π-electron-rich anilinyl substituent. Chloride abstraction from the monosubstituted product is therefore more favorable than chloride abstraction from the starting dichlorophosphine, and disubstitution is favored.

Scheme 3

Reagents and conditions: AlCl3 (3 equiv), N,N-diethylaniline (2 equiv), CH2Cl2, room temperature (RT), 36 h.

Reagents and conditions: n>an class="Chemical">AlCl3 (3 equiv), N,N-diethylaniline (2 equiv), CH2Cl2, room temperature (RT), 36 h.

From these results, it was clear that the n>an class="Chemical">AlCl3-generated phosphenium ion would not allow monosubstitution in most cases. As a result, we next examined AgOSO2CF3 as a chloride-abstracting reagent. Previously, we have shown that AgOSO2CF3 can be used to convert chlorophosphine complexes into phosphine triflate complexes, which react in the same fashion as phosphenium ion complexes.[15,16] Reaction of 1 with AgOSO2CF3 led to [W(CO)5{PPhCl(OSO2CF3)}] (3) (Scheme ), which was characterized in solution as a reactive intermediate (δ 31P = 162.5, 1JPW = 376 Hz) but was not isolated.

Scheme 4

Reagents and conditions: AgOSO2CF3 (1.3 equiv), CH2Cl2, RT, 3 h.

Reagents and conditions: n>an class="Chemical">AgOSO2CF3 (1.3 equiv), CH2Cl2, RT, 3 h.

The phosphine triflate 3 reacts with a wide range of organic nucleophiles, allowing for the controlled introduction of single substituents onto phosphorus. For example, the activated aromatic compounds N,N-diethylaniline and anisole readily add to 3, leading to the expected para-substituted products 4(16) and 5 (Scheme ). Both of these reactions are rapid at RT and high-yielding. Substitution can also be readily directed to the ortho position by blocking the para position, as demonstrated in the reaction of 3 with N,N-dimethyl-p-toluidine to form compound 6, in which the chlorophenylphosphine unit has added ortho to the N(CH3)2 group (Scheme ).

Scheme 5

Reagents and conditions: (i) N,N-Diethylaniline (2 equiv), CH2Cl2, RT, rapid. (ii) Anisole (4 equiv), CH2Cl2, RT, 30 min. (iii) N,N-Dimethyl-p-toluidine (2 equiv), CH2Cl2, rapid.

Reagents and conditions: (i) n>an class="Chemical">N,N-Diethylaniline (2 equiv), CH2Cl2, RT, rapid. (ii) Anisole (4 equiv), CH2Cl2, RT, 30 min. (iii) N,N-Dimethyl-p-toluidine (2 equiv), CH2Cl2, rapid.

The reactivity of 3 was probed further with reactions with aromatic substrates that are less activated toward electrophilic aromatic substitution, toluene, biphenyl, and naphthalene. Although the reactions are slower than those of anisole and aniline, compound 3 activates all of these substrates, leading to p-tolyl, p-phenylphenyl, and naphthyl chlorophenylphosphine complexes 7, 8, and 9, respectively (Scheme ). By contrast, the diphenyl phosphine triflate tungsten complex [W(CO)5{P(OSO2CF3)Ph2}] we described previously does not react with any of these substrates,[15] clearly showing that 3 is more electrophilic. The greater electrophilicity of 3 can be attributed to the electron-withdrawing Cl substituent, which enhances electrophilicity at P. Compound 3 does not activate benzene or chlorobenzene.

Scheme 6

Reagents and conditions. (i) Toluene (15 equiv), CH2Cl2, RT, 36 h. (ii) Biphenyl (10 equiv), CH2Cl2, RT, and 60 h. (iii) Naphthalene (10 equiv), CH2Cl2, RT, 48 h.

Reagents and conditions. (i) n>an class="Chemical">Toluene (15 equiv), CH2Cl2, RT, 36 h. (ii) Biphenyl (10 equiv), CH2Cl2, RT, and 60 h. (iii) Naphthalene (10 equiv), CH2Cl2, RT, 48 h.

One of our interests is the application of the methodology described here to bidentate ligands. To examine this possibility, 3 was added to di-p-tolyl ether, with the expectation that a PPhCl unit could be added to the position ortho to the ether linkage in both rings. Diaryl ethers form the backbones of several catalytically useful bisphosphine ligands.[18] However, the observed product 10 results instead from addition of a single PPh unit to a position bridging the ortho carbons of both phenyl rings (Scheme ). This reaction is an exception to the typical monosubstitution observed in reactions with 3. The reactivity can be attributed to the proximity of the second ortho H atom to the P center. A similar electrophilic aromatic substitution has been used to form the metal-free phosphine from di-p-tolyl ether and PPhCl2 but required a temperature of 130 °C.[19]

Scheme 7

Reagents and conditions. (i) Di-p-tolyl ether (2.5 equiv), CH2Cl2, RT, 12 h. (ii) 2,7,9,9-Tetramethyl xanthene (1.5 equiv), CH2Cl2, RT, 2 h.

Reagents and conditions. (i) n>an class="Chemical">Di-p-tolyl ether (2.5 equiv), CH2Cl2, RT, 12 h. (ii) 2,7,9,9-Tetramethyl xanthene (1.5 equiv), CH2Cl2, RT, 2 h.

The disubstitution reaction observed with di-p-tolyl ether can be prevented if a more rigid bisaromatic substrate is used. The substrate 2,7,9,9-tetramethyl xanthene, which also has the same backbone as a number of useful bisphosphine ligands,[8b,18a,20] was added to 3, leading to substitution in the 4 position of one of the aromatic rings, as expected (Scheme ). The monosubstitution is confirmed by the loss of symmetry, the appearance of four chemically inequivalent methyl groups in the 1H NMR and 13C NMR spectra, and the appearance of a 1JPC of 34.3 Hz in the 13C resonance of C in the 4 position. Unfortunately, attempts to add a second PClPh unit in the 5 position were not successful, probably as a result of the steric size of the metal complexes.

The nonaromatic nucleophile allyltrimethylsilane (allylTMS) also reacts readily with 3, leading to the chloroallyl phosphine complex 12 (Scheme ). The newly introduced allyl substituent is readily identified in the 1H NMR spectrum of the product, which shows peaks for the CH2 group at δ 3.39 and alkenyl H atoms at δ 5.26 (2H) and δ 5.68.

Scheme 8

Reagents and conditions: allylTMS (3 equiv), CH2Cl2, RT, rapid.

Reagents and pan class="Chemical">conditions: allylTMS (3 equiv), n>an class="Chemical">CH2Cl2, RT, rapid.

The second substitution step can be achieved by converting the chlorophosphines formed in the first step into triflates using silver triflate (Scheme ). Ferrocene was then added to all of the various phosphine triflate intermediates, leading to a series of phenyl-ferrocenyl phosphines, with a variety of substituents in the third position (see Scheme and Chart ). The majority of the chlorophosphines formed above can be substituted using this methodology, with some exceptions described below. Isolated yields range from 86 to 94%. Conversion to the triflate requires 2–3 h at RT for most precursors. Once the triflate has been formed, ferrocene addition is rapid. In all cases, the successful addition of ferrocene is readily apparent from the loss of symmetry in one of the two ferrocene Cp rings, apparent in the 1H and 13C spectra. The 13C resonances for the P-bound Cp ring also show 31P coupling, confirming the P–C bond formation.

Scheme 9

Chart 1

In some cases, the second substitution can be carried out using AlCl3 as the chloride abstractor. For example, p-tolyl, p-phenylphenyl, and naphthyl chlorophenylphosphine complexes 7, 8 and 9 were successfully converted to the ferrocenyl phosphines 19, 20, and 21, respectively, using AlCl3 and ferrocene; however, the yields were lower than those of the AgOSO2CF3 reactions. By contrast, anisyl and xanthyl chlorophenylphosphine complexes 5 and 11 did not react with AlCl3 and ferrocene. We attribute this lack of reactivity to the quenching of the AlCl3 Lewis acidity via interaction with the oxygen of the anisyl and xanthyl groups present in these compounds.

One exception to the generality of the AgOSO2CF3 methodology occurs with the N,N-diethylaniline-substituted complex [W(CO)5{P(Cl)Ph(p-C6H4NEt2)}] (4). Attempts to abstract chloride from 4 using AgOSO2CF3 resulted in an insoluble precipitate, rather than the desired triflate intermediate. Addition of AlCl3 to 4 led to a blue solution and the formation of a secondary phosphine complex (evident from large 1JHP in the 31P spectrum of the reaction mixture), rather than a phosphenium ion, presumably via a radical process. However, if the reactive substrate is added to the solution prior to the chloride abstraction with AlCl3, the desired electrophilic substitution reaction occurs. This is illustrated here by the addition of allylTMS and then AlCl3 to compound 4, which leads to the allyl-anilinyl-phenyl phosphine complex 23 (Scheme ).[16]

Scheme 10

Reagents and conditions: allylTMS (3 equiv), AlCl3 (1 equiv), CH2Cl2, RT, rapid.

Reagents and conditions: allylTMS (3 equiv), n>an class="Chemical">AlCl3 (1 equiv), CH2Cl2, RT, rapid.

Compound 6, formed from the addition of N,N-dimethyl-p-toluidine to 1, also reacts with chloride abstractors in a unique fashion. Abstraction of chloride from 6 with either AlCl3 or AgOSO2CF3 leads to a product with a 31P chemical shift of δ 230.1. The fact that both chloride abstractors appear to give the same product suggests that the AgOSO2CF3 reaction does not form a phosphine triflate, as it does in all other cases. The chemical shift is also not consistent with a phosphenium ion complex, which would be expected to appear close to δ 429, the observed shift for [W(CO)5{PPh2}][AlCl4].[15] Instead, we propose that these reactions are leading to the internally base-coordinated phosphenium ion complex 24 (Scheme ). In contrast to the precursor 6, the 1H NMR spectrum of 24 shows two chemically inequivalent N-bound methyl groups at δ 2.67 and 3.39. Furthermore, these resonances both show 31P couplings of 4.2 and 10.2 Hz, respectively. The methyl group inequivalence and 31P coupling provide strong evidence for N to P coordination. Further support for the proposed structure of 24 comes from the DFT/B3LYP-optimized structure (Figure ). Both N-coordinated and uncoordinated structures were optimized, and the N-coordinated structure was found to be more stable by 5.5 kcal/mol. The calculated P–N distance of 2.146 Å is very long for a P–N single bond (typical value of 1.683 Å[21]) but well within the sum of the van der Waals radii (3.35 Å).[22] The Mayer bond order was calculated as 0.436. These calculations indicate that the N→P dative bond is weak, probably as a result of the steric constraints of the resulting ring system. For comparison, an X-ray crystal structure of a compound with an amido donor and a phosphonium acceptor connected by the same organic backbone showed P–N distances of 1.842(7) and 1.839(6),[23] whereas a similar amine-coordinated phosphine showed a P–N distance of 3.014(3) Å,[24] and amine-coordinated dithioxo- and diselenoxophosphoranes showed P–N distances of 2.038(8) Å[25] and 2.039(5) Å, respectively.[26]

Scheme 11

Reagents and conditions: (i) AlCl3 (1.1 equiv), CH2Cl2, RT, rapid. (ii) Indole (1.1 equiv), CH2Cl2, RT, rapid.

Figure 1

DFT-optimized structure of the cation of compound 24. Hydrogen atoms are omitted for clarity. Selected distances (Å) and angles (deg): P–N = 2.146, P–W = 2.440, P–C1 = 1.826, C1–C2 = 1.387, C2–N = 1.470, P1–C1–C2 = 99.5, C1–C2–N = 106.7, C2–N–P = 83.9, and N–P–C1 = 70.0.

DFT-optimized strun>an class="Chemical">cture of the cation of compound 24. Hydrogen atoms are omitted for clarity. Selected distances (Å) and angles (deg): P–N = 2.146, P–W = 2.440, P–C1 = 1.826, C1–C2 = 1.387, C2–N = 1.470, P1–C1–C2 = 99.5, C1–C2–N = 106.7, C2–N–P = 83.9, and N–P–C1 = 70.0.

Reagents and conditions: (i) n>an class="Chemical">AlCl3 (1.1 equiv), CH2Cl2, RT, rapid. (ii) Indole (1.1 equiv), CH2Cl2, RT, rapid.

We were not able to isolate compound 24, so a derivative has been formed to supn>port its characterization. Compound 24 reacts with indole to form the indolyl phosphine complex 25, which has been fully characterized (Scheme ). Electrophilic addition of metal-coordinated phosphine triflates to indole is well-established,[11,15] and this reaction demonstrates that 24 shows the same reactivity as analogous phosphine triflate complexes, providing further evidence for a weak P–N bond.

To illustrate the range of substrates that can be added in the second step, the chloro-allyl-phenyl phosphine complex 12 was chosen. It was converted into the allyl-phenyl-triflate phosphine complex 26 via the reaction with AgOSO2CF3 (Scheme ). Addition of ferrocene led to the allyl-ferrocenyl phosphine complex 27. Addition of N,N-diethylaniline to 26 led to the expected allyl-p-anilinyl phosphine complex 23, which was also synthesized previously by introducing the groups in the opposite order.[16] The reaction of 26 with phenylacetylene led to the alkynyl-allyl phosphine complex 28.

Scheme 12

Reagents and conditions: CH2Cl2, RT. (i) AgOSO2CF3 (1.2 equiv), 12 h. (ii) Ferrocene (1 equiv), rapid. (iii) N,N-Diethylaniline (2 equiv), rapid. (iv) Phenylacetylene (3.7 equiv), 2 h.

Reagents and conditions: n>an class="Chemical">CH2Cl2, RT. (i) AgOSO2CF3 (1.2 equiv), 12 h. (ii) Ferrocene (1 equiv), rapid. (iii) N,N-Diethylaniline (2 equiv), rapid. (iv) Phenylacetylene (3.7 equiv), 2 h.

In general, the second substrate addition is limited to a narrower range of substrates ben>an class="Chemical">cause the phosphenium ion or phosphine triflate intermediate is less electrophilic than the intermediate in the first addition, which has an electron-withdrawing chloro substituent. Unlike compound 3, compound 26 does not react with toluene, naphthalene, or biphenyl. To apply this sequential strategy to phosphine formation, the least reactive substrate should be added first.

If the free phosphine is the desired final product, removal of the W(CO)5 unit can be readily achieved via the photolysis of phosphine complexes in the presence of bis(diphenylphosphino)ethane (dppe).[15] This reaction occurs via the photolytic dissociation of a CO ligand, followed by the coordination of one end of the bidentate phosphine. The other end of the phosphine then displaces the desired product, with [W(CO)4(κ2-dppe)] as the side product.[15] This reaction is a variation of the thermal method originally developed by Mathey et al.[27] Using this strategy, we transformed the tungsten phosphine complexes 19 and 22 into the free phosphines 29 and 30, respectively, using 1.2 equiv of dppe (Scheme ). The conversion on both reactions is quantitative by 31P NMR, and the products were obtained in high yields after flash chromatography purification.

Scheme 13

Reagents and conditions: dppe (1.2 equiv), UV radiation (260 nm max.), tetrahydrofuran (THF), RT, 3 h.

Reagents and conditions: n>an class="Chemical">dppe (1.2 equiv), UV radiation (260 nm max.), tetrahydrofuran (THF), RT, 3 h.

Conclusions

Metal-coordinated dichlorophenylphosphine is a useful precursor for electrophilic substitution reactions. If AlCl3 is used to abstract chloride, disubstituted products are formed, but if AgOSO2CF3 is used, controlled monosubstitution can be achieved. The chloro-triflate intermediate used in these reactions is more strongly electrophilic than the previously described phosphine triflate complexes, allowing the activation of substrates as unreactive as toluene. This greatly widens the range of potential substrates that can be used to form phosphine substituents. Substitution of the second chloro substituent with a different substrate leads to phosphines with three different substituents, which are P-stereogenic. Furthermore, all of these reactions can be carried out at RT or lower. Thus far, this methodology is not enantioselective; that is, it leads to chiral racemic phosphines. A future challenge is to develop an asymmetric version of this methodology.

Experimental Section

General Comments

All procedures except for flash chromatography were carried out using standard Schlenk techniques or in a glovebox under a nitrogen atmosphere. Diethyl ether, pentane, toluene, and THF were distilled from Na/benzophenone. Dichloromethane was purified using solvent purification columns containing alumina, followed by vacuum distillation from P2O5. CDCl3 was vacuum-distilled from P2O5. CD2Cl2 and C6D6 were used as received. Solvents for flash chromatography were not purified. Aluminum chloride was purified by sublimation and stored under an inert atmosphere. All other reagents were used as received. Photolysis reactions were carried out in Pyrex vessels using a Rayonet photochemical reactor equipped with nine lamps having a maximum output at 260 nm. NMR spectra were recorded on a Varian Mercury 300 spectrometer at 300.177 MHz (1H), 121.514 MHz (31P), 75.479 MHz (13C{1H}), or 282.231 MHz (19F), or on a Varian Inova 500 at 125.62 MHz (13C{1H}), in CDCl3 or C6D6. IR spectra were recorded on a Digilab FTIR in CH2Cl2 solution. Elemental analyses were carried out by the Analytical and Instrumentation Laboratory in the Department of Chemistry at the University of Alberta. 2,7,9,9-Tetramethyl xanthene was prepared according to the published procedure.[28] Compounds 1–4, 7, 12, and 28 were synthesized as previously described.[16]

Synthesis of [W(CO)5{PPhCl(p-C6H4OCH3)}] (5)

A solution of [W(CO)5{P(OSO2CF3)(Cl)Ph}] (3) was prepared by dissolving [W(CO)5{PPhCl2}] (1, 160.0 mg, 0.318 mmol) and AgOSO2CF3 (106.3 mg, 0.414 mmol) in CH2Cl2 (6 mL), stirring for 3 h, and filtering. Anisole (138 μL, 1.273 mmol) was added and the solution was stirred for 30 min, resulting in a color change to orange. The solvent was removed in vacuo and the residue was purified by flash chromatography (silica gel, 10/90 v/v diethyl ether/petroleum ether), leading to a yellow oil. Yield: 133 mg, 73%. IR (νCO, CH2Cl2, cm–1): 2078 (w), 1948 (vs). 31P{1H} NMR (CDCl3): δ 95.0 (s, 1JPW = 283 Hz). 1H NMR (CDCl3): δ 3.80 (s, 3H, OCH), 6.94 (ddd, 2H, 3JHH = 9.0 Hz, 4JHP = 4.8 Hz, 5JHH = 2.1 Hz, −C6HOCH3), 7.36–7.62 (m, 7H, 5H of Ph and 2H of −C6HOCH3). 13C{1H} NMR (CDCl3): δ 55.7 (s, −OCH3), 114.4 (d, 3JCP = 11.9 Hz, −CH4OCH3), 128.8 (d, 3JCP = 10.6 Hz, Ph), 129.4 (d, 1JCP = 36.5 Hz, ipso-CH4OCH3), 130.4 (d, 2JCP = 14.0 Hz, −CH4OCH3), 131.3 (d, 4JCP = 1.7 Hz, Ph), 133.9 (d, 2JCP = 16.9 Hz, Ph), 134.0 (d, 1JCP = 34.3 Hz, ipso-Ph), 162.7 (d, 4JCP = 1.7 Hz, −CH4OCH3), 196.2 (d, 2JCP = 7.3 Hz, 1JCW = 126.7 Hz, cis-CO), 199.3 (d, 2JCP = 31.0 Hz, trans-CO). Compound 5 was isolated as an oil. As a result, satisfactory elemental analysis could not be obtained. Full spectroscopic data are provided in the Supporting Information, and compound 18, which is derived from 5, has been fully characterized.

Synthesis of [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}(Cl)Ph}] (6)

A solution of [W(CO)5{PPhCl(OSO2CF3)}] (3) was prepared from [W(CO)5{PPhCl2}] (1, 150.0 mg, 0.298 mmol) and AgOSO2CF3 (99.6 mg, 0.388 mmol) in CH2Cl2 (6 mL) as described above. N,N-Dimethyl-p-toluidine (86 μL, 0.597 mmol) was added, resulting in a color change to yellow. The solvent was removed under reduced pressure, and the residue was purified by flash chromatography (silica gel, 20/80 v/v diethyl ether/petroleum ether) and crystallized as yellow crystals by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 163 mg, 87%. IR (νCO, CH2Cl2, cm–1): 2076 (w), 1944 (vs). 31P{1H} NMR (CDCl3): δ 87.2 (s, 1JPW = 270 Hz). 1H NMR (CDCl3): δ 2.01 (s, 6H, N(CH3)), 2.49 (s, 3H, C6H3CH3), 7.19 (dd, 1H, 3JHH = 7.8 Hz, 4JHP = 6.0 Hz, arene CH), 7.33 (dm, 1H, 3JHH = 7.8 Hz, arene CH), 7.38–7.48 (m, 3H, Ph), 7.70–7.78 (m, 2H, Ph), 7.92 (dm, 1H, 3JHP = 11.7 Hz, arene CH). 13C{1H} NMR (CDCl3): δ 21.7 (s, C6H3CH3), 46.3 (s, N(CH3)2), 123.9 (d, 3JCP = 5.1 Hz, arene C), 128.7 (d, 3JCP = 11.3 Hz, Ph), 131.3 (s, arene C), 131.3 (d, 2JCP = 8.5 Hz, arene C), 132.3 (d, 2JCP = 16.3 Hz, Ph), 133.9 (d, 4JCP = 1.7 Hz, Ph), 135.8 (d, 1JCP = 38.9 Hz, arene ipso-C), 136.7 (d, 3JCP = 8.5 Hz, arene ipso-C), 140.0 (d, 1JCP = 35.5 Hz, ipso-Ph), 153.0 (d, 2JCP = 11.3 Hz, arene ipso-C), 196.9 (d, 2JCP = 7.9 Hz, 1JCW = 127.3 Hz, cis-CO), 199.6 (d, 2JCP = 32.1 Hz, trans-CO). Anal. Calcd for C20H17ClNO5PW: C, 39.93; H, 2.85; N, 2.33. Found: C, 39.93; H, 2.85; N, 2.42.

Synthesis of [W(CO)5{P(Cl)(p-C6H4Ph)Ph}] (8)

A solution of [W(CO)5{P(OSO2CF3)(Cl)Ph}] (3) was prepared by dissolving [W(CO)5{PPhCl2}] (1, 140 mg, 0.278 mmol) and AgOSO2CF3 (93 mg, 0.362 mmol) in CH2Cl2 (6 mL), stirring for 3 h, and filtering. Biphenyl (407.8 mg, 2.784 mmol) was added and the solution was stirred for 60 h at RT, resulting in a color change to red. The solvent was removed in vacuo, and the residue was purified by flash chromatography (silica gel, 5/95 v/v diethyl ether/petroleum ether). The very pale yellow crystals of [W(CO)5{P(Cl)(p-C6H4Ph)Ph}] (8) were obtained by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 92 mg, 53%. IR (νCO, CH2Cl2, cm–1): 2079 (w), 1950 (vs). 31P{1H} NMR (CDCl3): δ 95.4 (s, 1JPW = 283 Hz). 1H NMR (CDCl3): δ 7.37–7.57 (m, 6H, 5H of C6H4Ph and 1H of Ph), 7.60–7.79 (m, 8H, 4H of −C6HPh and 4H of Ph). 13C{1H} NMR (CDCl3): δ 127.5 (s, −C6H4Ph), 127.5 (d, 3JCP = 11.3 Hz, Ph), 128.6 (s, −C6H4Ph), 129.0 (d, 3JCP = 10.7 Hz, −CH4Ph), 129.2 (s, −C6H4Ph), 131.0 (d, 2JCP = 15.2 Hz, −CH4Ph), 131.7 (d, 4JCP = 1.7 Hz, Ph), 131.9 (d, 2JCP = 15.7 Hz, Ph), 137.3 (d, 1JCP = 33.2 Hz, ipso-Ph), 139.0 (d, 1JCP = 33.2 Hz, ipso-C6H4Ph), 139.7 (d, 5JCP = 1.3 Hz, ipso-C6H4Ph), 144.7 (d, 4JCP = 2.3 Hz, ipso-CH4Ph), 196.1 (d, 2JCP = 7.3 Hz, 1JCW = 126.7 Hz, cis-CO), 199.10 (d, 2JCP = 30.9 Hz, 1JCW = 141.6 Hz, trans-CO). Anal. Calcd for C23H14ClO5PW: C, 44.51; H, 2.27. Found: C, 44.52; H, 2.33.

Synthesis of [W(CO)5{P(Cl)(1-C10H7)Ph}] (9)

A solution of [W(CO)5{P(OSO2CF3)(Cl)Ph}] (3) was prepared by dissolving [W(CO)5{PPhCl2}] (1, 160.0 mg, 0.318 mmol) and AgOSO2CF3 (98.1 mg, 0.382 mmol) in CH2Cl2 (8 mL), stirring for 3 h, and filtering. Naphthalene (407.8 mg, 3.182 mmol) was added and the solution was stirred for 48 h at RT, resulting in a color change to red. The solvent was removed in vacuo, and the residue was purified by flash chromatography (silica gel, 2/98 v/v diethyl ether/petroleum ether). Pale yellow crystals of [W(CO)5{P(Cl)(1-C10H7)Ph}] (9) were obtained by cooling a saturated pentane solution to −20 °C. Yield: 125 mg, 66%. IR (νCO, CH2Cl2, cm–1): 2079 (w), 1950 (vs). 31P{1H} NMR (CDCl3): δ 95.9 (s, 1JPW = 283 Hz). 1H NMR (CDCl3): δ 7.42–7.71 (m, 8H, 3H of Ph, 5H of naphthyl), 7.88–7.97 (m, 3H, 2H of Ph, 1H of naphthyl), 8.31 (dm, 1H, naphthyl). 13C{1H} NMR (CDCl3): δ 126.4 (d, JCP = 13.5 Hz), 127.6 (s), 128.0 (d, JCP = 1.7 Hz), 128.9 (d, JCP = 4.4 Hz), 129.0 (d, JCP = 10.2 Hz), 129.1 (s), 129.37 (s), 131.0 (d, JCP = 14.6 Hz), 131.7 (d, JCP = 1.7 Hz), 132.4 (d, JCP = 13.0 Hz), 133.3 (d, JCP = 18.0 Hz), 134.6 (d, JCP = 1.7 Hz), 135.6 (d, 1JCP = 33.2 Hz), 139.1 (d, 1JCP = 33.8 Hz), 196.1 (d, 2JCP = 7.3 Hz, 1JCW = 126.1 Hz, cis-CO), 199.0 (d, 2JCP = 31.0 Hz, trans-CO). Satisfactory elemental analysis could not be obtained for Compound 9. Full spectroscopic data are provided in the Supporting Information, and compound 21, which is derived from 9, has been fully characterized.

Synthesis of [W(CO)5{PPh(C12H6O(CH3)2)}] (10)

A solution of [W(CO)5{P(OSO2CF3)(Cl)Ph}] (3) was prepared by dissolving [W(CO)5{PPhCl2}] (1, 120 mg, 0.239 mmol) and AgOSO2CF3 (79.7 mg, 0.310 mmol) in CH2Cl2 (5 mL), stirring for 3 h, and filtering. Di-p-tolyl ether (118.5 mg, 0.598 mmol) was added and the solution was stirred for 12 h at RT, resulting in a color change to brown. The solvent was removed in vacuo, and the residue was purified by flash chromatography (alumina, 5/95 v/v diethyl ether/petroleum ether). Colorless crystals of [W(CO)5{PPh(C12H6O(CH3)2)}] (10) were obtained by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 81 mg, 54%. 31P{1H} NMR (CDCl3): δ −20.7 (s, 1JPW = 252 Hz). 1H NMR (CDCl3): δ 2.23 (s, 6H, CH), 7.01–7.14 (m, 6H, −C12HO(CH3)2), 7.31–7.35 (m, 3H, Ph), 7.41–7.50 (m, 2H, Ph). 13C{1H} NMR: δ 21.1 (s, CH3), 116.4 (d, 1JPC = 27 Hz, Ar ipso-P), 118.1 (d, JPC = 3 Hz, Ar), 129.0 (d, JPC = 6 Hz, Ph), 130.8 (d, JPC = 2 Hz, Ph), 132.9 (d, JPC = 8 Hz, Ph), 133.1 (d, JPC = 1 Hz, Ar), 133.7 (d, JPC = 8 Hz, Ar), 133.8 (d, JPC = 7 Hz, Ar), 137.4 (d, JPC = 21 Hz, Ph ipso-P), 151.3 (s, Ar ipso-O), 197.0 (d, 2JPC = 5 Hz, 1JCW = 76 Hz, cis-CO), 200.0 (d, 2JPC = 14 Hz, trans-CO). Anal. Calcd for C25H17O6PW: C, 47.80; H, 2.73. Found: C, 47.75; H, 2.79.

Synthesis of [W(CO)5{PPhCl(C13H5O(CH3)4)}] (11)

A solution of [W(CO)5{P(OSO2CF3)(Cl)Ph}] (3) was prepared by dissolving [W(CO)5{PPhCl2}] (1, 130 mg, 0.259 mmol) and AgOSO2CF3 (86.4 mg, 0.336 mmol) in CH2Cl2 (5 mL), stirring for 3 h, and filtering. 2,7,9,9-Tetramethyl xanthene (92.3 mg, 0.388 mmol) was added and the solution was stirred for 12 h at RT, resulting in a color change to brown. The solvent was removed in vacuo, and the residue was purified by flash chromatography (silica gel, 20/80 v/v diethyl ether/petroleum ether). Pale yellow crystals of [W(CO)5{PPhCl(C13H5O(CH3)4)}] (11) were obtained by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 122 mg, 67%. IR (νCO, CH2Cl2, cm–1): 2078 (w), 1947 (vs). 31P{1H} NMR (CDCl3): δ 91.8 (s, 1JPW = 281 Hz). 1H NMR (CDCl3): δ 1.44 (s, 3H, CH), 1.71 (s, 3H, CH), 2.25 (s, 3H, CH), 2.48 (s, 3H, CH), 6.07 (d, 1H, 3JHH = 8.1 Hz, C13HO(CH3)4), 6.74 (dm, 1H, 3JHH = 8.4 Hz, C13HO(CH3)4), 7.10 (d, 1H, 4JHH = 1.5 Hz, C13HO(CH3)4), 7.40 (d, 1H, 4JHH = 1.8 Hz, C13HO(CH3)4), 7.41–7.46 (m, 3H, Ph), 7.61 (dm, 1H, 3JHP = 12.0 Hz, C13HO(CH3)4), 7.68–7.76 (m, 2H, Ph). 13C{1H} NMR (CDCl3): δ 21.2 (s, C13H5O(CH3)4), 21.6 (s, C13H5O(CH3)4), 29.5 (s, C13H5O(CH3)4), 34.1 (s, C13H5O(CH3)4), 34.5 (s, 4JCP = 1.7 Hz, quaternary-CH5O(CH3)4), 115.7 (s, CH5O(CH3)4), 123.4 (d, 1JCP = 34.3 Hz, ipso-CH5O(CH3)4), 126.1 (s, CH5O(CH3)4), 128.2 (s, CH5O(CH3)4), 129.0 (d, 3JCP = 11.3 Hz, Ph), 129.4 (d, 2JCP = 5.6 Hz, CH5O(CH3)4), 129.8 (s, ipso-CH5O(CH3)4), 130.5 (d, 4JCP = 1.7 Hz, CH5O(CH3)4), 131.1 (d, 2JCP = 16.4 Hz, Ph), 131.6 (d, 3JCP = 3.9 Hz, ipso-CH5O(CH3)4), 132.0 (d, 4JCP = 1.7 Hz, Ph), 133.1 (d, 3JCP = 8.5 Hz, CH5O(CH3)4), 133.2 (s, ipso-CH5O(CH3)4), 138.4 (d, 1JCP = 33.2 Hz, ipso-Ph), 147.5 (s, ipso-CH5O(CH3)4), 148.1 (d, 2JCP = 8.5 Hz, ipso-CH5O(CH3)4), 196.5 (d, 2JCP = 7.9 Hz, 1JCW = 126.7 Hz, cis-CO), 199.6 (d, 2JCP = 31.6 Hz, trans-CO). Anal. Calcd for C28H22ClO6PW: C, 47.72; H, 3.15. Found: C, 47.41; H, 3.08.

Synthesis of [W(CO)5{PPh(C5H4FeCp)(p-C6H4OCH3)}] (18)

[W(CO)5{PPhCl(p-C6H4OCH3)}] (8, 80 mg, 0.139 mmol) and AgOSO2CF3 (42.9 mg, 0.167 mmol) were dissolved in CH2Cl2 (4 mL). This solution was stirred for 2 h, resulting in the formation of a white precipitate, which was removed via filtration through Celite. This solution was shown to contain [W(CO)5{PPh(OSO2CF3)(p-C6H4OCH3)}] (13). Ferrocene (51.8 mg, 0.278 mmol) was added and the solution was stirred for 15 min, resulting in a color change from yellow to dark green. The solvent was removed in vacuo, and the residue was purified by flash chromatography (alumina, 20/80 v/v diethyl ether/petroleum ether). Orange crystals of [W(CO)5{PPh(C5H4FeCp)(p-C6H4OCH3)}] (18) were obtained by cooling a saturated pentane/diethyl ether solution to −20 °C. Yield: 95 mg, 94%. IR (νCO, CH2Cl2, cm–1): 2070 (w), 1935 (vs). 31P{1H} NMR (CDCl3): δ 9.9 (s, 1JPW = 246 Hz). 1H NMR (CDCl3): δ 3.86 (s, 3H, OCH3), 4.01 (s, 5H, C5H4FeCp), 4.16 (m, 1H, C5H4FeCp), 4.31 (m, 1H, C5H4FeCp), 4.51 (m, 2H, C5H4FeCp), 6.97 (ddd, 2H, 3JHH = 8.4 Hz, 4JHP = 3.0 Hz, 5JHH = 1.8 Hz, −C6H4OCH3), 7.32–7.39 (m, 5H, Ph), 7.46 (ddd, 2H, 3JHP = 10.5 Hz, 3JHH = 8.4 Hz, 5JHH = 2.7 Hz, −C6H4OCH3). 13C{1H} NMR (CDCl3): δ 55.6 (s, −OCH3), 69.9 (s, C5H4FeCp), 71.5 (d, 3JCP = 7.3 Hz, C5H4FeCp), 71.9 (d, 3JCP = 6.7 Hz, C5H4FeCp), 73.3 (d, 2JCP = 9.6 Hz, C5H4FeCp), 74.6 (d, 2JCP = 14.0 Hz, C5H4FeCp), 79.7 (d, 1JCP = 46.1 Hz, ipso-C5H4FeCp), 113.9 (d, 3JCP = 11.3 Hz, −C6H4OCH3), 128.2 (d, 3JCP = 9.6 Hz, Ph), 128.3 (d, 1JCP = 47.9 Hz, ipso-C6H4OCH3), 129.8 (d, 4JCP = 1.7 Hz, Ph), 132.1 (d, 2JCP = 11.3 Hz, Ph), 134.8 (d, 2JCP = 13.5 Hz, −C6H4OCH3), 139.4 (d, 1JCP = 43.9 Hz, ipso-Ph), 161.3 (d, 4JCP = 1.7 Hz, −C6H4OCH3), 197.7 (d, 2JCP = 6.7 Hz, 1JCW = 125.6 Hz, cis-CO), 199.3 (d, 2JCP = 20.8 Hz, 1JCW = 142.43 Hz, trans-CO). Anal. Calcd for C28H21FeO6PW: C, 46.44; H, 2.92. Found: C, 46.22; H, 2.98.

Synthesis of [W(CO)5{P(C5H4FeCp)(p-C6H4CH3)Ph}] (19)

The compound [W(CO)5{P(Cl)(p-C6H4CH3)Ph}] (7, 80 mg, 0.143 mmol) and AgOSO2CF3 (132.8 mg, 0.172 mmol) were dissolved in CH2Cl2 (4 mL). The solution was stirred for 2 h, resulting in the formation of a white precipitate, which was removed via filtration through Celite. The solution was shown to contain [W(CO)5{P(OSO2CF3)(p-C6H4CH3)Ph}] (14). Ferrocene (53.3 mg, 0.286 mmol) was added, resulting in a color change to brown. The solvent was removed in vacuo, and the residue was purified by flash chromatography (alumina, 10/90 v/v diethyl ether/petroleum ether). Orange crystals of [W(CO)5{P(C5H4FeCp)(p-C6H4CH3)Ph}] (19) were obtained by cooling a saturated pentane/diethyl ether solution to −20 °C. Yield: 95 mg, 94%. IR (νCO, CH2Cl2, cm–1): 2071 (w), 1936 (vs). 31P{1H} NMR (CDCl3): δ 10.9 (s, 1JPW = 244 Hz). 1H NMR (CDCl3): δ 2.41 (s, 3H, −CH), 3.99 (s, 5H, C5H4FeCp), 4.21 (m, 1H, C5HFeCp), 4.28 (m, 1H, C5HFeCp), 4.52 (m, 2H, C5HFeCp), 7.24 (dd, 2H, 3JHH = 7.8 Hz, 5JHH = 1.8 Hz, −C6HCH3), 7.35–7.43 (m, 7H, 2H of −C6H4CH3, 5H of Ph). 13C NMR (CDCl3): δ 21.5 (d, 5JCP = 1.1 Hz, −CH3), 69.9 (s, C5H4FeCp), 71.7 (d, 3JCP = 7.3 Hz, CH4FeCp), 71.8 (d, 3JCP = 6.7 Hz, CH4FeCp), 73.7 (d, 2JCP = 10.7 Hz, CH4FeCp), 74.3 (d, 2JCP = 12.9 Hz, CH4FeCp), 79.3 (d, 1JCP = 46.1 Hz, CH4FeCp), 128.2 (d, 3JCP = 9.6 Hz, Ph), 129.1 (d, 3JCP = 10.1 Hz, −CH4CH3), 129.9 (d, 4JCP = 2.3 Hz, Ph), 132.4 (d, 2JCP = 11.3 Hz, Ph), 133.0 (d, 2JCP = 12.4 Hz, −CH4CH3), 134.3 (d, 1JCP = 45.7 Hz, ipso-CH4CH3), 138.8 (d, 1JCP = 43.3 Hz, ipso-Ph), 140.5 (d, 4JCP = 1.7 Hz, −CH4CH3), 197.7 (d, 2JCP = 6.8 Hz, 1JCW = 126.1 Hz, cis-CO), 199.3 (d, 2JCP = 20.8 Hz, trans-CO). Anal. Calcd for C28H21FeO6PW: C, 47.49; H, 2.99. Found: C, 47.77; H, 3.11.

Synthesis of [W(CO)5{P(C5H4FeCp)(p-C6H4Ph)Ph}] (20)

[W(CO)5{P(Cl)(p-C6H4Ph)Ph}] (8, 80 mg, 0.129 mmol) and AgOSO2CF3 (40 mg, 0.155 mmol) were dissolved in CH2Cl2 (5 mL). This solution was stirred for 2 h, resulting in the formation of a white precipitate, which was removed via filtration through Celite. The solution was shown to contain [W(CO)5{P(OSO2CF3)(p-C6H4Ph)Ph}] (15). Ferrocene (48 mg, 0.258 mmol) was added, resulting in a color change to dark green. The solvent was removed in vacuo, and the residue was purified by flash chromatography (alumina, 20/80 v/v diethyl ether/petroleum ether). Orange crystals of [W(CO)5{PPh(C5H4FeCp)(p-C6H4Ph)}] (20) were obtained by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 90 mg, 91%. IR (νCO, CH2Cl2, cm–1): 2070 (w), 1936 (vs). 31P{1H} NMR (CDCl3): δ 11.3 (s, 1JPW = 246 Hz). 1H NMR (CDCl3): δ 3.93 (s, 5H, C5H4FeCp), 4.21 (m, 2H, C5HFeCp), 4.46 (m, 2H, C5HFeCp), 7.26–7.48 (m, 10H, 7H of C6H4Ph and 3H of Ph), 7.53–7.60 (m, 4H, 2H of −C6H4Ph and 2H of Ph). 13C{1H} NMR (CDCl3): δ 70.0 (s, C5H4FeCp), 71.9 (d, 3JCP = 3.9 Hz, CH4FeCp), 71.9 (d, 3JCP = 3.3 Hz, CH4FeCp), 74.0 (d, 2JCP = 9.4 Hz, CH4FeCp), 74.2 (d, 2JCP = 9.4 Hz, CH4FeCp), 79.0 (d, 1JCP = 45.9 Hz, CH4FeCp), 126.9 (d, 3JCP = 10.0 Hz, Ph), 127.4 (s, −C6H4Ph), 128.2 (s, −C6H4Ph), 128.4 (d, 3JCP = 10.0 Hz, −CH4Ph), 129.2 (s, −C6H4Ph), 130.2 (d, 4JCP = 2.2 Hz, Ph), 132.7 (d, 2JCP = 11.6 Hz, −CH4Ph), 133.2 (d, 2JCP = 12.1 Hz, Ph), 136.7 (d, 1JCP = 44.8 Hz, ipso-Ph), 138.2 (d, 1JCP = 33.2 Hz, ipso-CH4Ph), 140.1 (d, 5JCP = 1.1 Hz, ipso-C6H4Ph), 142.8 (d, 4JCP = 1.7 Hz, ipso-CH4Ph), 197.6 (d, 2JCP = 7.3 Hz, 1JCW = 126.1 Hz, cis-CO), 199.2 (d, 2JCP = 21.6 Hz, trans-CO). Anal. Calcd for C33H23FeO5PW: C, 51.46; H, 3.01. Found: C, 51.16; H, 3.03.

Synthesis of [W(CO)5{P(C5H4FeCp)(1-C10H7)Ph}] (21)

[W(CO)5{P(Cl)(1-C10H7)Ph}] (9, 70 mg, 0.118 mmol) and AgOSO2CF3 (39.3 mg, 0.153 mmol) were dissolved in CH2Cl2 (4 mL). This solution was stirred for 2.5 h, resulting in the formation of a white precipitate, which was removed via filtration through Celite. The solution was shown to contain [W(CO)5{P(OSO2CF3)(1-C10H7)Ph}] (16), and the conversion was quantitative. Ferrocene (43.8 mg, 0.235 mmol) was added and the solution was stirred for 15 min, resulting in a color change to dark green. The solvent was removed in vacuo, and the residue was purified by flash chromatography (alumina, 20/80 v/v diethyl ether/petroleum ether). Orange crystals of [W(CO)5{PPh(C5H4FeCp)(1-C10H7)}] (21) were obtained by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 78 mg, 89%. IR (νCO, CH2Cl2, cm–1): 2070 (w), 1936 (vs). 31P{1H} NMR (CDCl3): δ 12.3 (s, 1JPW = 247 Hz). 1H NMR (CDCl3): δ 3.99 (s, 5H, C5H4FeCp), 4.27 (m, 1H, C5HFeCp), 4.33 (m, 1H, C5HFeCp), 4.55 (m, 2H, C5HFeCp), 7.42–7.58 (m, 8H, 3H of Ph, 5H of naphthyl), 7.80–7.94 (m, 4H, 2H of Ph, 2H of naphthyl). 13C{1H} NMR (CDCl3): δ 69.9 (s, C5H4FeCp), 71.8 (d, 3JCP = 7.3 Hz, CH4FeCp), 71.9 (d, 3JCP = 6.7 Hz, CH4FeCp), 74.0 (d, 2JCP = 11.9 Hz, CH4FeCp), 74.3 (d, 2JCP = 12.4 Hz, CH4FeCp), 79.0 (d, 1JCP = 46.7 Hz, CH4FeCp), 127.1 (s), 127.8 (s), 127.9 (s), 128.0 (s), 128.4 (d, JCP = 9.6 Hz), 128.7 (d, JCP = 12.4 Hz), 128.9 (s), 130.3 (d, JCP = 2.2 Hz), 132.6 (d, JCP = 11.3 Hz), 132.8 (d, JCP = 11.9 Hz), 133.4 (d, JCP = 12.4 Hz), 133.8 (d, JCP = 1.7 Hz), 135.5 (d, d, 1JCP = 43.4 Hz), 137.9 (d, 1JCP = 43.9 Hz), 197.7 (d, 2JCP = 6.8 Hz, 1JCW = 126.1 Hz, cis-CO), 199.1 (d, 2JCP = 21.4 Hz, trans-CO). Anal. Calcd for C31H21FeO5PW: C, 50.03; H, 2.84. Found: C, 49.92; H, 2.85.

Synthesis of [W(CO)5{PPh(C5H4FeCp)(C13H5O(CH3)4)}] (22)

[W(CO)5{PPhCl(C13H5O(CH3)4)}] (11, 70 mg, 0.099 mmol) and AgOSO2CF3 (33.2 mg, 0.129 mmol) were dissolved in CH2Cl2 (4 mL). This solution was stirred for 3 h, resulting in the formation of a white precipitate, which was removed via filtration through Celite. The solution was shown to contain [W(CO)5{PPh(OSO2CF3)(C13H5O(CH3)4)}] (17). The yield is quantitative by NMR spectroscopy. Ferrocene (40.0 mg, 0.199 mmol) was then added and the resulting solution was stirred for 15 min, resulting in a color change to brown from yellow. The solvent was removed in vacuo, and the residue was purified by flash chromatography (alumina, 10/90 v/v diethyl ether/petroleum ether). Orange crystals of [W(CO)5{PPh(C5H4FeCp)(p-C6H4OCH3)}] (22) were obtained by cooling a saturated pentane/CH2Cl2 solution to −20 °C. Yield: 78 mg, 92%. IR (νCO, CH2Cl2, cm–1): 2070 (w), 1935 (vs). 31P{1H} NMR (CDCl3): δ 4.8 (s, 1JPW = 244 Hz). 1H NMR (CDCl3): δ 1.40 (s, 3H, CH), 1.69 (s, 3H, CH), 2.23 (s, 3H, CH), 2.25 (s, 3H, CH), 3.91 (m, 5H, C5H4FeCp), 3.97 (m, 1H, C5HFeCp), 4.49 (m, 1H, C5HFeCp), 4.56 (m, 1H, C5HFeCp), 4.69 (m, 1H, C5HFeCp), 5.79 (d, 1H, 3JHH = 8.4 Hz, C13HO(CH3)4), 6.41 (dm, 1H, 3JHP = 12.0 Hz, C13HO(CH3)4), 6.71 (dm, 1H, 3JHH = 8.1 Hz, C13HO(CH3)4), 7.08 (d, 1H, 4JHH = 1.8 Hz, C13HO(CH3)4), 7.20 (d, 1H, 4JHH = 1.5 Hz, C13HO(CH3)4), 7.43–7.47 (m, 3H, Ph), 7.71–7.78 (m, 2H, Ph). 13C{1H} NMR (CDCl3): δ 21.2 (s, C13H5O(CH3)4), 21.5 (s, C13H5O(CH3)4), 29.7 (s, C13H5O(CH3)4), 34.1 (s, C13H5O(CH3)4), 34.5 (s, 4JCP = 1.7 Hz, quaternary-CH5O(CH3)4), 69.9 (s, C5H4FeCp), 70.7 (d, 2JCP = 9.0 Hz, CH4FeCp), 72.1 (d, 3JCP = 2.3 Hz, CH4FeCp), 72.7 (d, 3JCP = 5.1 Hz, CH4FeCp), 77.0 (d, 2JCP = 21.4 Hz, CH4FeCp), 79.2 (d, 1JCP = 46.8 Hz, ipso-CH4FeCp), 115.9 (s, CH5O(CH3)4), 125.9 (s, CH5O(CH3)4), 126.4 (d, 1JCP = 41.7 Hz, ipso-CH5O(CH3)4), 128.0 (s, CH5O(CH3)4), 128.2 (d, 3JCP = 10.7 Hz, Ph), 128.7 (d, 4JCP = 1.1 Hz, CH5O(CH3)4), 129.9 (s, ipso-CH5O(CH3)4), 130.1 (d, 4JCP = 2.3 Hz, Ph), 130.4 (d, 2JCP = 5.7 Hz, CH5O(CH3)4), 130.9 (d, 3JCP = 3.9 Hz, ipso-CH5O(CH3)4), 132.1 (d, 3JCP = 8.4 Hz, ipso-CH5O(CH3)4), 132.5 (d, 2JCP = 12.9 Hz, Ph), 132.6 (s, ipso-CH5O(CH3)4), 135.8 (d, 1JCP = 47.9 Hz, ipso-Ph), 147.6 (s, ipso-CH5O(CH3)4), 147.9 (d, 2JCP = 4.5 Hz, ipso-CH5O(CH3)4), 197.8 (d, 2JCP = 7.3 Hz, 1JCW = 126.1 Hz, cis-CO), 199.4 (d, 2JCP = 22.0 Hz, trans-CO). Anal. Calcd for C38H31FeO6PW: C, 53.42; H, 3.66. Found: C, 53.01; H, 3.73.

Reaction of [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}(Cl)Ph}] (6) with AlCl3

The compound [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}(Cl)Ph}] (6, 25.0 mg, 0.042 mmol) and AlCl3 (6.2 mg, 1.1 equiv, 0.046 mmol) were dissolved in CH2Cl2 (0.7 mL), resulting in the immediate formation of a dark yellow solution, which was shown to be [W(CO)5{PPh{C6H3(2-N(CH3)2)(5-CH3)}}][AlCl4] (24). Compound 24 is stable for short periods in dichloromethane solution but decomposes upon crystallization. This reaction was also carried out in CD2Cl2 for NMR spectroscopy. Conversion is quantitative according to 31P NMR spectroscopy. 31P{1H} NMR (CD2Cl2): δ 230.1 (s, 1JPW = 310 Hz). 1H NMR (CD2Cl2): δ 2.58 (s, 3H, C6H3CH3), 2.62 (d, 3JHP = 3.0 Hz, 3H, N(CH3)), 3.34 (d, 3JHP = 12.0 Hz, 3H, N(CH3)), 7.43 (dd, 1H, 3JHH = 9.0 Hz, 4JHP = 3.0 Hz, arene CH), 7.49–7.84 (m, 7H, Ph). 13C{1H} NMR (CD2Cl2): δ 22.3 (s, C6H3CH3), 49.3 (s, N(CH3)2), 50.6 (d, 2JCP = 5.3 Hz, N(CH3)2), 119.6 (d, 3JCP = 5.3 Hz, arene C), 128.4 (d, 3JCP = 13.6 Hz, arene ipso-C), 130.1 (d, J = 4.5 Hz, arene C), 130.7 (s, arene C), 130.8 (s, arene C), 136.2 (d, JCP = 22.6 Hz, arene ipso-C), 136.6 (s, Ph), 138.3 (d, JCP = 1.5 Hz, arene C), 145.9 (d, 1JCP = 9.1 Hz, ipso-Ph), 146.9 (s, arene ipso-C), 192.9 (d, 2JCP = 7.5 Hz, cis-CO), 194.6 (d, 2JCP = 31.7 Hz, trans-CO).

Synthesis of [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}(C8H6N)Ph}] (25)

The compound [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}(Cl)Ph}] (6, 90.0 mg, 0.151 mmol) and indole (19.45 mg, 1.1 equiv, 0.166 mmol) were dissolved in CH2Cl2 (3.0 mL), resulting in the formation of a yellow solution. This solution was added to AgOSO2CF3 (46.51 mg, 1.2 equiv, 0.181 mmol) and stirred for 2 h, resulting in the formation of a pink solution with a white precipitate. The white precipitate was removed via filtration through Celite. The solution was shown to contain [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}(C8H6N)Ph}] (25). The solvent was removed under reduced pressure, the residue was purified by flash chromatography (Florisil, 10/90 diethyl ether/petroleum ether), and the product was obtained as yellow crystals by cooling a saturated pentane/diethyl ether solution to −20 °C. Yield: 92 mg, 90%. IR (νCO, CH2Cl2, cm–1): 2065 (w), 1930 (vs). 31P{1H} NMR (CDCl3): δ −12.1 (s, 1JPW = 243 Hz). 1H NMR (CDCl3): δ 2.11 (s, 6H, N(CH3)2), 2.24 (3H, arene-CH3), 7.63–6.95 (13H, Ph and indolyl), 8.51 (br, 1H, NH). 13C{1H} NMR (CDCl3): δ 21.4 (s, arene-CH3), 46.3 (s, N(CH3)2), 111.9 (s, indole Ar), 120.9 (s, indole Ar), 122.5 (s, indole Ar), 123.3 (s, arene), 123.7 (d, JCP = 6 Hz, arene), 128.3 (d, JCP = 10 Hz, indole C2), 128.5 (d, JCP = 3 Hz, arene ipso-CH3), 129.7 (d, JCP = 44 Hz, indole C3), 129.8 (d, JCP = 1.5 Hz, indole arene), 132.7 (d, JCP = 1.5 Hz, arene), 133.7 (s, Ph), 133.7 (s, Ph), 133.8 (s, arene), 133.9 (s, arene ipso-P), 134.1 (d, JCP = 8 Hz, indole C7′), 136.3 (d, JCP = 43 Hz, Ph ipso-P), 137.8 (d, JCP = 7 Hz, indole C3′), 155.9 (d, JCP = 10 Hz, arene ipso-N), 198.6 (d, 2JCP = 7 Hz, 1JCW = 127 Hz, cis-CO), 200.9 (d, 2JCP = 22 Hz, trans-CO). Anal. Calcd for C28H23O5N2PW: C, 49.29; H, 3.40; N, 4.11. Found: C, 49.55; H, 3.50; N, 3.99.

Synthesis of [W(CO)5{P(CH2CHCH2)(C5H4FeCp)Ph}] (27)

The compound [W(CO)5{P(CH2CHCH2)(Cl)Ph}] (12, 70.0 mg, 0.138 mmol) and AgOSO2CF3 (42.4 mg, 0.165 mmol) were dissolved in CH2Cl2 (6 mL). This solution was stirred for 12 h at RT, resulting in the formation of a white precipitate, which was removed via filtration through Celite. The solution was shown to contain [W(CO)5{P(CH2CHCH2)(OSO2CF3)Ph}] (26), and conversion is quantitative by NMR spectroscopy. Ferrocene (26.4 mg, 0.142 mmol) was added, resulting in a color change to brown. The solvent was removed under reduced pressure, the residue was purified by flash chromatography (alumina, 20/80 diethyl ether/petroleum ether), and the product was obtained as orange crystals by cooling a saturated hexane solution to −20 °C. Yield: 67 mg, 86%. IR (νCO, CH2Cl2, cm–1): 2070 (w), 1934 (vs). 31P{1H} NMR (CDCl3): δ −0.4 (s, 1JPW = 244 Hz). 1H NMR (CDCl3): δ 3.34 (m, 2H, −CH2CHCH2), 4.30 (s, 5H, C5H4FeCp), 4.33 (m, 1H, C5HFeCp), 4.38 (m, 1H, C5HFeCp), 4.56 (m, 2H, C5HFeCp), 5.20–5.27 (m, 2H, −CH2CHCH2), 5.88 (m, 1H, −CH2CHCH2), 7.32–7.50 (m, 5H, Ph). 13C{1H} NMR (CDCl3): δ 40.2 (d, 1JCP = 26.5 Hz, −CH2CHCH2), 69.9 (s, C5H4FeCp), 71.2 (d, 2JCP = 7.9 Hz, CH4FeCp), 71.7 (d, 3JCP = 6.3 Hz, CH4FeCp), 71.9 (d, 3JCP = 7.5 Hz, CH4FeCp), 74.8 (d, 2JCP = 15.4 Hz, CH4FeCp), 78.7 (d, 1JCP = 44.5 Hz, ipso-CH4FeCp), 120.6 (d, 2JCP = 11.1 Hz, −CH2CHCH2), 128.4 (d, 3JCP = 9.1 Hz, −Ph), 129.8 (d, 4JCP = 2.1 Hz, Ph), 130.8 (d, 2JCP = 10.0 Hz, Ph), 131.6 (d, 3JCP = 4.8 Hz, −CH2CHCH2), 137.8 (d, 1JCP = 39.7 Hz, ipso-Ph), 197.7 (d, 2JCP = 6.9 Hz, 1JCW = 125.0 Hz, cis-CO), 199.2 (d, 2JCP = 21.7 Hz, trans-CO). Anal. Calcd for C24H19FeO5PW: C, 43.80; H, 2.91. Found: C, 44.18; H, 3.07.

Synthesis of [W(CO)5{P(CH2CHCH2)(CCPh)Ph}] (28)

The compound [W(CO)5{P(CH2CHCH2)(Cl)Ph}] (12, 70.0 mg, 0.138 mmol) and AgOSO2CF3 (42.4 mg, 0.165 mmol) were dissolved in CH2Cl2 (6 mL). This solution was stirred for 12 h at RT, resulting in the formation of a white precipitate, which was removed via filtration through Celite. The solution was shown to contain [W(CO)5{P(CH2CHCH2)(OSO2CF3)Ph}] (26), and conversion is quantitative by NMR spectroscopy. Phenylacetylene (62 μL, 0.512 mmol) was added and the solution was stirred for 2 h, resulting in a color change to brown. The solvent was removed in vacuo and the residue was purified by flash chromatography (alumina, 10/90 v/v diethyl ether/petroleum ether), leading to a pale yellow oil. Yield: 59 mg, 75%. IR (νCO, CH2Cl2, cm–1): 2073 (w), 1940 (vs). 31P{1H} NMR (CDCl3): δ −13.2 (s, 1JPW = 243 Hz). 1H NMR (CDCl3): δ 3.01 (m, 2H, −CH2CHCH2), 4.99–5.15 (m, 2H, −CH2CHCH2), 5.63 (m, 1H, −CH2CHCH2), 7.30–7.54 (m, 8H, Ph), 7.62–7.72 (m, 2H, Ph). 13C{1H} NMR (CDCl3): δ 41.8 (d, 1JCP = 27.6 Hz, −CH2CHCH2), 82.1 (d, 1JCP = 79.4 Hz, −CCPh), 110.2 (d, 2JCP = 12.5 Hz, −CCPh), 120.8 (d, 3JCP = 10.6 Hz, −CH2CHCH2), 121.2 (d, 3JCP = 2.3 Hz, ipso-CCPh), 128.9 (s, −CCPh), 129.0 (d, 3JCP = 10.6 Hz, Ph), 130.0 (d, 2JCP = 8.4 Hz, −CH2CHCH2), 130.5 (d, 2JCP = 12.5 Hz, Ph), 130.7 (d, 4JCP = 2.2 Hz, Ph), 130.8 (s, −CCPh), 133.4 (d, 1JCP = 47.3 Hz, ipso-Ph), 196.9 (d, 2JCP = 7.3 Hz, 1JCW = 125.5 Hz, cis-CO), 199.7 (d, 2JCP = 22.5 Hz, 1JCW = 145.8 Hz, trans-CO). Compound 28 is thermally unstable and decomposes on storage. As a result, satisfactory elemental analysis could not be obtained. Full spectroscopic data are provided in the Supporting Information.

Synthesis of {P(C5H4FeCp)(p-C6H4CH3)Ph} (29)

Compound 19 (120 mg, 0.169 mmol) and dppe (81.0 mg, 0.203 mmol) were dissolved in THF (3 mL) and irradiated with UV for 3 h, resulting in a color change from orange to red. The solvent was removed under reduced pressure, and the residue was purified by flash chromatography (alumina, 10/90 v/v diethyl ether/petroleum ether). After purification, the free phosphine {P(C5H4FeCp)(p-C6H4CH3)Ph} (29) was obtained as orange powder. Yield: 59 mg, 91%. 31P{1H} NMR (C6D6): δ −16.6 (s). 1H NMR (C6D6): δ 2.01 (s, 3H, −CH), 3.96 (m, 5H, C5H4FeCp), 4.05–4.10 (m, 4H, C5HFeCp), 7.24 (dd, 2H, 3JHH = 6.0 Hz, −C6HCH3), 7.00–7.07 (m, 3H, 3H of Ph), 7.40–7.50 (m, 4H, 2H of −C6HCH3 and 2H of Ph). 13C{1H} NMR (C6D6): δ 21.1 (s, −CH3), 69.4 (s, C5H4FeCp), 69.4 (s, C5H4FeCp), 70.9 (d, 3JCP = 3.0 Hz, CH4FeCp), 70.9 (d, 3JCP = 4.5 Hz, CH4FeCp), 72.9 (d, 2JCP = 12.1 Hz, CH4FeCp), 73.4 (d, 2JCP = 16.6 Hz, CH4FeCp), 76.9 (d, 1JCP = 7.6 Hz, CH4FeCp), 128.2 (s, Ph), 128.3 (s, −CH4CH3), 129.2 (d, 3JCP = 6.8 Hz, −CH4CH3), 133.6 (d, 2JCP = 18.9 Hz, Ph), 134.1 (d, 2JCP = 19.6 Hz, Ph), 136.3 (d, 1JCP = 10.6 Hz, ipso-CH4CH3), 138.4 (s, ipso-CH4CH3), 140.5 (d, 1JCP = 11.3 Hz, ipso-CH4CH3). Anal. Calcd for C23H21FeP: C, 71.90; H, 5.51. Found: C, 71.64; H, 5.60.

Synthesis of {PPh(C5H4FeCp)(C13H5O(CH3)4)} (30)

Compound 22 (130 mg, 0.152 mmol) and dppe (72.8 mg, 0.183 mmol) were dissolved in THF (3 mL) and irradiated with UV for 3 h, resulting in a color change from orange to red. The solvent was removed under reduced pressure, and the residue was purified by flash chromatography (alumina, 20/80 v/v diethyl ether/petroleum ether). After purification, the free phosphine {PPh(C5H4FeCp)(C13H5O(CH3)4)} (30) was obtained as orange powder. Yield: 71 mg, 88%. 31P{1H} NMR (C6D6): δ −25.1 (s). 1H NMR (C6D6): δ 1.36 (s, 3H, CH), 1.39 (s, 3H, CH), 2.03 (s, 3H, CH), 2.05 (s, 3H, CH), 3.97 (m, 1H, CHFeCp), 3.99 (m, 5H, C5H4FeCp), 4.10 (m, 1H, C5HFeCp), 4.16 (m, 1H, C5HFeCp), 4.40 (m, 1H, C5HFeCp), 6.66 (dm, 1H, 3JHH = 6.0 Hz, C13HO(CH3)4), 6.75 (d, 1H, 3JHP = 9.0 Hz, C13HO(CH3)4), 6.96 (m, 1H, C13HO(CH3)4), 7.01–7.07 (m, 5H, 2H of C13HO(CH3)4 and 3H of Ph), 7.67–7.73 (m, 2H, Ph). 13C{1H} NMR (C6D6): δ 20.8 (s, C13H5O(CH3)4), 21.0 (s, C13H5O(CH3)4), 30.2 (s, C13H5O(CH3)4), 32.6 (s, C13H5O(CH3)4), 34.5 (d, 4JCP = 1.5 Hz, quaternary-CH5O(CH3)4), 69.4 (s, C5H4FeCp), 69.4 (s, C5H4FeCp), 70.9 (d, 3JCP = 1.5 Hz, CH4FeCp), 71.2 (d, 3JCP = 6.0 Hz, CH4FeCp), 72.7 (d, 2JCP = 5.3 Hz, CH4FeCp), 74.7 (d, 2JCP = 25.7 Hz, CH4FeCp), 76.3 (d, 1JCP = 9.1 Hz, ipso-CH4FeCp), 116.4 (s, CH5O(CH3)4), 125.8 (s, CH5O(CH3)4), 126.9 (s, CH5O(CH3)4), 128.1 (CH5O(CH3)4), 128.1 (Ph), 128.4 (s, CH5O(CH3)4), 130.3 (d, 4JCP = 1.6 Hz, ipso-Ph), 130.3 (s, Ph), 131.8 (d, 3JCP = 3.9 Hz, ipso-CH5O(CH3)4), 132.1 (s, CH5O(CH3)4), 132.5 (d, 3JCP = 5.3 Hz, ipso-CH5O(CH3)4), 133.7 (s, Ph), 134.0 (s, Ph), 139.5 (d, 1JCP = 9.8 Hz, ipso-Ph), 149.2 (s, ipso-CH5O(CH3)4), 150.6 (d, 2JCP = 13.6 Hz, ipso-CH5O(CH3)4). Anal. Calcd for C33H31FeOP: C, 74.72; H, 5.89. Found: C, 74.88; H, 6.21.

Computational Details

All gas-phase computations for compound 24 were performed using the hybrid density functional B3LYP level of theory,[29] as implemented in Gaussian 09 electronic structure code.[30] Vibrational frequency computations were performed to ensure that the optimized structures are true minima. The basis sets LANL2DZ[31] for W and 6-31g(d,p)[32] for other atoms were used for optimization and frequency computations, and the basis sets LANL2TZ(f)[31] for W and 6-311g+(2d,p)[33] for other atoms were used for the single-point computations. The LANL2TZ(f) basis set information was extracted from the EMSL basis set library.[34] The energies (ΔG) given are corrected for zero-point vibrational energies. Mayer bond orders[35] on the optimized structure were obtained using the AOMix program.[36]