Element–Hydrogen Bond Activations at Cationic Platinum Centers To

Apr 15, 2019 - Element–Hydrogen Bond Activations at Cationic Platinum Centers To Produce Silylene, Germylene, Stannylene, and Stibido Complexes...
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Article Cite This: Organometallics XXXX, XXX, XXX−XXX

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Element−Hydrogen Bond Activations at Cationic Platinum Centers To Produce Silylene, Germylene, Stannylene, and Stibido Complexes Rory Waterman,† Rex C. Handford,‡ and T. Don Tilley*,‡ †

Department of Chemistry, University of Vermont, Burlington, Vermont 05405, United States Department of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460, United States

‡

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S Supporting Information *

ABSTRACT: Reactions of [(dippe)PtMe(Et 2 O)][BAr f4 ] (4[BArf4], dippe = 1,2-bis(diisopropylphosphino)ethane; Arf = 3,5-(CF3)2C6H3) with Mes2EH2 (Mes = mesityl) liberate methane and produce silylene, germylene, or stannylene products [(dippe)Pt(H)EMes2][BArf4] (E = Si, 1[BArf4]; Ge, 8; Sn, 9). In contrast, treatment of 4[BArf4] with tertiary silanes HSiR3 (R = Ph, Et, OEt) failed to give the expected cationic silyl complexes but instead produced the bridging hydride [(dippe)Pt(μ-H)]2[BArf4]2 (10) along with the corresponding disilane Si2R6. Complex 10 reacts with primary stibines RSbH2 (R = Mes, dmp) to afford dimeric stibido complexes [(dippe)Pt(μ-SbHR)]2[BArf4]2 (R = Mes, 11; dmp, 12) via Sb−H bond activation.

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INTRODUCTION An established method for the synthesis of metal silylene complexes involves formal transfer of a silylene unit (:SiR2) from a simple organosilane (e.g., R2SiH2) to a metal center.1−3 For instance, the mesityl complex Cp*(iPr2MeP)Fe(Mes) reacts with dmpSiH3 (dmp = 2,6-(2,4,6-Me3C6H2)C6H3; Mes = mesityl) with elimination of mesitylene to produce the silylene complex Cp*(iPr2MeP) (H)FeSiH(dmp) (eq 1).4 The mechanism of this transformation appears to involve sequential Si−H bond activations, by oxidative addition and then by α-H migration.3

at these metal centers as pathways to silylene complexes. Related, earlier work demonstrated that the cationic silylene complex [(dippe) Pt(H)SiMes2][MeB(C6F5)3] (1[MeB(C6F5)3], eq 2; dippe = 1,2-bis(diisopropylphosphino)ethane)

is formed by abstraction of methide from (dippe)PtMe(SiHMes2) with B(C6F5)3.14 This abstraction presumably generates a vacant coordination site, which then allows αhydrogen migration from the silyl ligand to the platinum center, furnishing the PtSi linkage. This work suggested that complexes of the type [L2PtR]+ might serve as useful, general precursors to complexes containing silylene ligands, or other low-valent main group fragments as ligands. In general, cationic platinum(II) alkyl complexes have attracted considerable attention in bond activations that enable stoichiometric and catalytic transformations. For example, such complexes have been investigated as models for late transitionmetal α-olefin polymerization catalysts.15 In addition, cationic platinum complexes (primarily with diamine or diimine ligands) have been investigated in the context of C−H bond activation and alkane functionalization.15,16 Several cationic platinum alkyl complexes supported by phosphine ligands are also noteworthy,

Reactions of this type may be important in various metalmediated transformations of silicon compounds or, more generally, in reactions involving the formal transfer of lowvalent main group species. In particular, such processes have been implicated in catalytic reactions involving redistribution reactions of silanes (e.g., RSiH3 to R2SiH2 and SiH4),5 silane dehydropolymerization,6,7 and hydrosilylation.2,3 This type of silylene transfer has been employed in the synthesis of a variety of neutral and cationic silylene complexes with metals from groups 6 through 9,1,4,8−12 including the ruthenium complex [Cp*(PiPr3)(H)2RuSiH(R)]+ (R = aryl) which is catalytically active for alkene hydrosilylations.2,13 Given the importance of group 10 metals (especially platinum) in catalytic transformations of organosilane compounds, it is of interest to investigate “double Si−H activations” © XXXX American Chemical Society

Received: February 13, 2019

A

DOI: 10.1021/acs.organomet.9b00097 Organometallics XXXX, XXX, XXX−XXX

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Organometallics including an ethyl derivative with a β-agostic interaction.17 Kubas and coworkers have prepared a series of cation platinum methyl derivatives that readily activate sp2 C−H bonds and mediate the dimerization of benzene or toluene; these complexes also cleave B−C bonds in the relatively unreactive borate BArf4− (Arf = 3,5-(CF3)2C6H3).18,19 In this contribution, we describe routes to several new cationic platinum alkyl complexes and their use in providing synthetic routes to silylene, germylene, stannylene, and stibido complexes via activations of element-hydrogen bonds.

room temperature, and are related to the complexes [(R2PC2H4PR2)PtMe(OEt2)][BArf4] (R = Cy, Et) reported by Kubas and coworkers.17 The identity of the cation 4+ was confirmed via chemical derivatizations. Reaction of complex 4[B(C6F5)]4 with Lewis bases (L) in CH2Cl2 gave analytically pure adducts of the general formula [(dippe)PtMe(L)][B(C6F5)4] according to Scheme 1 (L = PPh3 (5), 90% yield; Si(NtBuCH)2 (6), 75% yield; 2,6lutidine (7), 81% yield). These complexes display NMR spectra that suggest Cs symmetry. Formation of Silylene, Germylene, and Stannylene Complexes. Complex 5 reacted with Mes2SiH2 in CD2Cl2 solution at 0 °C to liberate one equiv of CH4 (by 1H NMR spectroscopy) and form a yellow solution of the silylene complex [(dippe)Pt(H)SiMes2][BArf4] (1[BArf4], eq 4). Complex

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RESULTS AND DISCUSSION Cationic Platinum Complexes. These compounds were generally prepared by protonolysis of a Pt−C bond in an alkyl complex of the type (dippe)PtR2. Reaction of a CH2Cl2 solution of (dippe)Pt(CH2Ph)2 (2) with [NHMe2Ph][B(C6F5)4] resulted in formation of 1 equiv of toluene (by 1H NMR spectroscopy) and [(dippe)Pt(η3-CH2Ph)][B(C6F5)4] (3) as analytically pure colorless crystals in 71% isolated yield (eq 3). The η3-binding mode of the benzyl ligand was supported by observation of methylene resonances at δ 3.57 ppm and δ 68.4 ppm in the 1H and 13C{1H} NMR spectra, respectively.20

1[BArf4] is spectroscopically identical to 1[MeB(C6F5)3] except for resonances attributed to the respective borate counterions.14 In the original report of 1[MeB(C6F5)3], it was noted that the complex exhibited limited thermal stability and could not be isolated as a solid.14 For complex 1[BArf4], the same is true, yet 1[BArf4] is less thermally robust than the MeB(C6F5)3− derivative and decomposes at ambient temperature in CD2Cl2 solution with a half-life of ca. 2 h. One possibility for the increased stability of complex 1[MeB(C6F5)3] over that of 1[BArf4] may be some degree of interaction between the MeB(C6F5)3− counterion and the electron deficient silylene silicon center. The base-stabilized silylene complex [(dippe)PtH{SiMes2(DMAP)}][BArf4] (1[BArf4]·DMAP) was isolated as pale yellow crystals by treatment of complex 4[BArf4] with Mes2SiH2 in the presence of 4-(dimethylamino)pyridine (DMAP, eq 4). Complex 1[BArf4]·DMAP was also formed as the primary product of treating CD2Cl2 solutions of complex 1[BArf4] with DMAP. The spectroscopic data for 1[BArf4]· DMAP are virtually identical to that for the known MeB(C6F5)3− derivative [(dippe)PtH{SiMes2(DMAP)}][MeB(C6F5)3].14 Having established that silylene transfer from a secondary silane is viable for these platinum systems, related reactions involving additional group 14 systems were investigated. Reaction of complex 4[BArf4] with Mes2GeH2 in CH2Cl2 solution at −35 °C resulted in liberation of 1 equiv of CH4 (by 1H NMR spectroscopy) and isolation of analytically pure yellow crystals of the germylene complex [(dippe)Pt(H) GeMes2][BArf4] in 71% yield (8, eq 5).

Simple organosilanes RSiH3 (R = Ph, Mes, trip) and RR’SiH2 (R = Ph, Et) failed to react with complex 3 in CD2Cl2 at temperatures up to 50 °C prior to decomposition of the platinum benzyl compound to predominantly (dippe)PtCl2, as identified by 31P{1H} NMR spectroscopy.21 Thus, more reactive cationic platinum alkyl complexes were targeted. The cationic methyl complex [(dippe)PtMe(OEt2)]+ (4+) was isolated as the B(C 6 F 5 ) 4 (4[B(C 6 F 5 )] 4 ) and BAr f 4 (4[BArf4]) salts in good yields by reaction of ethereal solutions of (dippe)PtMe2 with [CPh3][B(C6F5)4] or [H(OEt2)2][BArf4], respectively (Scheme 1). Complexes 4[B(C6F5)]4 and 4[BArf4] exhibit broad, rather uninformative NMR spectra at Scheme 1. Reactions of [(dippe)PtMe(OEt2)]+ (4+) with Small-Molecule Substrates

In the 1H NMR spectrum of 8, a hydride resonance is observed at δ −2.26 ppm with cis and trans couplings to the B

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Organometallics dippe ligand of 5.6 and 109.2 Hz, respectively. The apparent Cs symmetry of the complex was confirmed in the 31P{1H} NMR spectrum, which showed two resonances for the dippe ligand. Repeated attempts to produce X-ray quality crystals of the complex were unsuccessful. Germylene species of group 10 metals are well known22−28 and in some cases can be prepared by addition of an isolable germylene to a low-valent metal precursor. Banaszak Holl and coworkers have established that such germylene complexes have a rich reaction chemistry associated with activations of various small molecules.29−31 Treatment of complex 4[BArf4] with Mes2SnH2 in CH2Cl2 solution at −35 °C in the dark gave the stannylene complex [(dippe)Pt(H)SnMes2][BArf4] (9) as an orange-red powder in 34% yield (eq 6). Monitoring the reaction by 1H and 31P{1H}

Figure 1. (a) Computed structure of the model silylene [(dmpe)Pt(H)SiPh2]+ (1*). (b) LUMO of 1*. (c) π-bonding orbital for the PtSi linkage of 1*.

Table 1. Bond Distances and Angles for the Computed Structures of [(dmpe)Pt(H)EPh2]+ (E = Si, Ge, Sn)

NMR spectroscopy (CD2Cl2) confirmed that CH4 is generated and that 9 is the major product of the reaction (>95% conversion to 9). Spectroscopic features of 9 parallel those of 1 and 8. A high degree of thermal and photochemical instability prohibited collection of reliable microanalytical data for 9; the decomposition products of 9 are numerous and were not identified. Regrettably, attempts to characterize 9 by its 119Sn NMR spectrum were unsuccessful. This is likely a consequence of the poor sensitivity of the nucleus, as well as the poor signal-to-noise expected for a resonance with Sn−H and Sn−P couplings. The synthesis of 9 is a rare example of a stannylene extrusion reaction.32,33 Stannylene complexes are known for a variety of metals, and these compounds are frequently prepared by coordination of a free stannylene to a low-valent metal precursor.34−36 Stannylene complexes have been prepared via α-migration reactions.32,33,37−39 Computational Investigations of [(dippe)Pt(H) EMes2]+ Complexes. Density functional theory (DFT) calculations of the model complex series [(dmpe)Pt(H) EPh2]+ (dmpe = 1,2-bis(dimethylphosphino)ethane; E = Si, Ge, Sn) were performed to compare structural properties of these closely related species. Optimization of the structures of [(dmpe)Pt(H)SiPh 2 ]+ (1*), [(dmpe)Pt(H)GePh 2 ]+ (8*), and [(dmpe)Pt(H)SnPh2]+ (9*) at the Perdew− Burke−Ernzerhof level of theory revealed similar square-planar coordination geometries about Pt. Effective core potentials were used for the Pt atoms of all three complexes and for the Sn atom of 9* to account for relativistic effects. The structure of 1*, as well as the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital − 9 [corresponding to π(PtSi)], is shown in Figure 1. Following periodic trends, the PtE distances lengthen from E = Si to Sn (Table 1). In all complexes, the Pt−H distances are roughly 1.63 Å, though the E···H distance increases from Si to Sn (Table 1). The long E···H distances indicate that there are minimal residual E···H bonding interactions in these complexes, suggesting that full α-H migration from E to Pt has occurred. Consistent with these findings is the lack of apparent 29Si satellites for the Pt−H resonance of 1+’s 1H NMR spectrum, possibly a consequence of the small magnitude expected for twobond Si−H coupling (2JSiH = ∼7−10 Hz).40 The structural

complex d (Å); ∠ (deg)

1*

8*

9*

d(Pt−E) d(Pt−H) d(E···H) ∠(Pt−E−H)

2.279 1.635 2.454 75.63

2.367 1.629 2.643 80.51

2.544 1.633 2.724 78.05

features of 1* are similar to those of the computed structure of [(dhpe)Pt(H)SiMe2]+ (dhpe = H2PCH2CH2PH2); the latter complex was found to possess minimal Si···H interactions in its ground state geometry.41 These features differ significantly from the structural and spectroscopic properties of [(dtbpe)Ni(μH)SiMes2]+ (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane), which features a strong Si···H interaction, as indicated by 1JSi−H = 43.4 Hz in its 1H NMR spectrum and by the Si···H distance of 1.63(7) Å in its solid-state molecular structure.42 DFT analyses of the model complex [(dmpe)Ni(μ-H) SiPh2]+ indicate that the 1s orbital of the μ-H atom interacts with a lobe of the π(NiSi) MO in forming the Ni(μ-H)Si unit. In contrast, the π(PtSi) MO of 1* shows no interaction with the nearby hydride ligand (Figure 1c); the related π(Pt Si) MOs of 8* and 9* are similar in this regard. The differences in the Ni and Pt complexes likely result from the enhanced ability of Pt to engage in stabilizing backbonding to the SiR2 unit. When backbonding is diminished (i.e., for Ni), interaction of nearby Ni−H bonding electron density with the electrophilic Si center stabilizes the NiSiR2 linkage. Si−Si Bond Formation. A presumed intermediate in the above extrusion reactions is a cationic complex with a −EHMes2 ligand. These cationic species are clearly unstable with respect to α-migrations, but may be trapped by small molecules to mediate reactions of the Pt−E bonds. For example, reaction of 4[BArf4] with a tertiary silane could lead to Si−H activation and a new cationic silyl complex. Treatment of CH2Cl2 solutions of 4[BArf4] with each 1 equiv of a silane (Ph3SiH, Et3SiH, or (EtO)3SiH) led to conversion of only half of the platinum starting material to [(dippe)Pt(μ-H)]2[BArf4]2 (10; Scheme 2). Similarly, reaction of 5 with excess silane by 1H and 31P NMR spectroscopy in CD2Cl2 revealed liberation of CH4 and nearly quantitative formation of 10. Additionally, the siliconC

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Organometallics

indenyl, R = Ph, Cy, Me) by Fontaine and Zargarian54 supports a catalytic cycle similar to that in Scheme 2. Complex 10 appears to be a thermodynamic sink in these reactions. Treating 4[BArf4] with excess (100 equiv) R3SiH (R = Ph, Et, OEt) in CD2Cl2 gave only 2 equiv of disilane per mole of 10 formed (i.e., 1 equiv of disilane per Pt center). Upon extended reaction times or heating, no additional disilane was formed prior to decomposition of 10 to multiple products including (dippe)PtCl2, as identified by 31P{1H} and 1H NMR spectroscopy. The reaction in acetone-d6 gave hydride 10 and disilane regardless of starting silane R3SiH (R = Ph, Et, OEt). Heating these reaction mixtures in acetone-d6 afforded no increased yield of disilane prior to decomposition of 10 to unidentified products. Milstein and coworkers have reported a facile catalytic dehydrocoupling of secondary silanols in acetone-d6 using [(dippe)Pt(μ-H)]2[OTf]2.44 The reason for the limited reactivity of 10 toward catalytic dehydrocoupling of silanes is unclear. It would appear that dimeric 10 does not dissociate sufficiently for further reaction (vida infra). A possible feature that may influence the propensity of these dimeric hydride species to dissociate is the Lewis basicity of the incoming ligand (a silane Si−H bond vs a silanol Si−H bond). Additionally, the Lewis basicity of the counter ion (OTf− vs BR−) may play a role. Sb−H Bond Activation. Reaction of complex 10 with primary stibines MesSbH2 and dmpSbH2 in CH2Cl2 resulted in H2 evolution and formation of dimeric stibido complexes [(dippe)Pt(μ-SbHR)]2[BArf4]2 (R = Mes, 11; dmp, 12) as analytically pure yellow crystals in 27 and 63% yield, respectively (eq 8).

Scheme 2. Proposed Mechanism for the Formation of 10 and Disilanes

containing products were identified by 29Si NMR spectroscopy as the disilanes R3Si−SiR3 (R = Ph, Et, OEt) by comparison to authentic samples. In each case, the yields of the disilanes are quantitative with respect to Pt as determined by 1H NMR spectroscopy. A more convenient preparation of complex 10 involves oxidation of the platinum hydride dimer [(dippe)PtH]219 with [Cp2Fe][BArf4], to give analytically pure yellow crystals in 76% yield (eq 7). The 31P{1H} NMR spectrum of 10 displayed a

resonance at δ 104.3 ppm, while the 1H NMR spectrum showed a complex multiplet for the hydride at δ −2.86 ppm, both of which are characteristic of a dimeric platinum hydride complex supported by a chelating R2PCH2CH2PR2 ligand.43,44 Monomeric cationic platinum hydride complexes have been reported.45,46 A likely mechanism for the formation of Si−Si bonds in this system would involve oxidative addition of 1 equiv of R3SiH to 4[BArf4] followed by reductive elimination of CH4. A second Si−H oxidative addition event would afford a cationic bis(silyl)platinum(IV) intermediate, which would reductively eliminate (R3Si)2 (Scheme 2). A model for the initial platinum(IV) intermediate in this potential mechanism comes from reaction of [(NN)PtMe][BArf4] (NN = N,N-bis(3methoxypropyl)dimethyldiazabutadiene) with triethylsilane to give [(NN)PtH(Me) (SiEt3)][BArf4], which is pseudo-octahedral due to coordination of a pendant methyl ether from the NN ligand.47 This cationic platinum(IV) complex is thermally unstable, but is readily observed. The relative stability of NNligated system over the potential dippe-supported intermediate is attributed to the propensity of phosphine-supported fivecoordinate Pt(IV) to undergo reductive elimination, often to form C−H bonds.48 Reductive elimination reactions that form Si−Si bonds are slightly rare.49−52 The highly related rhodium complex [(dippe)Rh(μ-H)]2 dehydrocouples secondary silanes by a mechanism that is virtually identical to the proposed stoichiometric dehydrocoupling by complex 4[BArf4].53 Study of silane dehydrocoupling using (1-Me-Ind)NiMe(PR3) (Ind =

The spectroscopic features of these two complexes are very similar, including low-field stibido proton resonances at δ −4.33 (11) and δ −5.99 ppm (12), which appear as triplets of triplets. Variation of temperature and field strength indicated that these resonances are the result of non-first-order coupling. However, an adequate simulation of the spin system could not be obtained, and apparent couplings are reported (see Experimental Section). The 31P{1H} NMR spectra of both complexes contain broad singlets for the dippe ligand, and variable temperature NMR analysis on each complex (CD2Cl2, −90 to 35 °C) did not resolve the 2JPP coupling constants. The NMR spectra are consistent with observation of a rapid exchange process that has a low activation barrier; inversion at antimony is a process that is consistent with these data. Related bridging phosphido complexes [(dppe)Pt(μ-PHMes)]2[BF4]2 (dppe = 1,2-bis(diphenylphosphino)ethane) reported by Glueck and coworkers have well-resolved syn and anti isomers.55,56 Presumably, the barrier to inversion is smaller for a substituted antimony center than that for phosphorus, based on periodic trends.57 The Mes derivative 11 exhibits limited thermal stability as compared to dmp derivative 12 and decomposes at ambient temperatures in the solid state over a period of days. Complex 11, however, is more crystalline than 12, and single crystals of 11 D

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Organometallics were grown from a CH2Cl2/pentane solvent system at −35 °C. The solid-state molecular structure of 11 is shown in Figure 2. Complex 11 bears an approximately tetrahedral Sb center with d(Pt−Sb) = 2.6307(8) Å.

species undergo E−H activations by [(dippe)PtMe(OEt2)]+, though the product of each reaction is markedly dependent on the identity of the hydride starting material. Complexes 4[B(C6F5)4] 4[BArf4] should serve as useful platforms for further exploration of activation and α-H migration of E−H bonds in main-group hydrides.

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EXPERIMENTAL SECTION

General Methods. All manipulations were performed under an atmosphere of dry nitrogen using Schlenk techniques and/or an M Braun glovebox. Dry, oxygen-free solvents were employed throughout. Elemental analyses were performed by the microanalytical laboratory at the University of California, Berkeley. Infrared spectra (Nujol mulls, KBr plates) were recorded using a Mattson Fourier transform infrared spectrometer at a resolution of 2 cm−1. NMR (1H, 13C{1H}, and 31 1 P{ H}) spectra were recorded on Bruker AVANCE 300 and 400 MHz NMR spectrometers and are reported with reference to solvent resonances (1H, 13C{1H}) or to an external H3PO4 standard (31P{1H}). X-ray diffraction data were collected on a Bruker Platform goniometer with a CCD detector (Smart Apex). Details of the crystallographic structure determination of 11 and DFT calculations of 1*, 8*, and 9* can be found in the Supporting Information. Complexes (COD)PtI2,64 (COD)Pt(CH2Ph)2,64 (COD)PtPh2,64 LiCH2tBu,65 (dippe)PtMe2,66 [(dippe)PtH]2,43 [HNMe2Ph][B(C6F5)4],67 [CPh3][B(C6F5)4],68 [H(OEt2)][BArf4],69 [CPh 3][BArf4],70 Mes2SiH2,71 Mes2GeH2,72 H2SnMes2,73 [Cp2Fe][BArf4],74 MesSbH2,75 and dmpSbH276 were prepared according to the literature protocols. All other chemicals were used as received. (dippe)Pt(CH2Ph)2 (2). A Schlenk flask was charged (COD)Pt(CH2Ph)2 (157 mg, 0.323 mmol) and dippe (85 mg, 0.323 mmol), and then 10 mL of CH2Cl2 was added via a cannula. The resulting colorless solution was allowed to stir for 4 h. The volatiles were removed under reduced pressure. The residual was washed with hexanes and extracted with hot benzene. The resulting colorless solution was filtered and lyophilized to give crude (dippe)Pt(CH2Ph)2 in nearly quantitative yield (198 mg, 0.283 mmol, 96%), which was used without further purification. 1H NMR (benzene-d6, 400 MHz): δ 7.49 (d, JHH = 7.2 Hz, 4H, Ar-H), 7.26 (t, JHH = 7.2 Hz, 4H, Ar-H), 7.01 (t, JHH = 7.2 Hz, 2H, Ar-H), 3.30 (t, 3JPH = 8 Hz, 2JPtH = 90 Hz, 4H, CH2), 1.89 (m, 4H, CH), 0.92 (dd, 3JHP = 15.2 Hz, 3JHH = 7.2 Hz, 12H, CH3), 0.88 (m, 4H, CH2), 0.77 (dd, 3JHP = 12.8 Hz, 3JHH = 6.8 Hz, 12H, CH3). 31P{1H} NMR (benzene-d6, 162 MHz): δ 64.7 (s, 1JPtP = 1887 Hz). [(dippe)Pt(η3-CH2Ph)][B(C6F5)4] (3). A Schlenk flask was charged with (dippe)Pt(CH2Ph)2 (198 mg, 0.283 mmol) and [HNMe2Ph][B(C6F5)4] (288 mg, 0.283 mmol). Cold CH2Cl2 (−78 °C, 10 mL) was introduced via a cannula. The resulting nearly colorless solution was allowed to warm and then stirred at ambient temperature for 1 h, and then the solvent was removed under reduced pressure. The residue was twice washed with ca. 5 mL of hexanes and then dissolved in 4 mL CH2Cl2, and the solution filtered. Pentane was layered (ca. 4 mL) on the solution, and the mixture cooled to −30 °C for 2 d to give colorless crystals of the title complex (247 mg, 0.201 mmol, 71%). 1H NMR (CD2Cl2, 400 MHz): δ 7.66 (m, 2H, Ar-H), 7.10 (t, JHH = 7.2 Hz, 1H, Ar-H), 6.32 (m, 2H, Ar-H), 3.57 (br, 2H, CH2), 2.48 (m, CH, 2H), 2.15 (m, 2H, CH), 2.04 (m, 2H, CH2), 1.68 (m, 2H, CH), 1.28 (dd, JHP = 16.0 Hz, JHH = 7.2 Hz, 6H, CH3), 1.22 (dd, 3JHP = 9.2 Hz, 3JHH = 2.8 Hz, 6H, CH3), 1.04 (dd, 3JHP = 18.8 Hz, 3JHH = 10.0 Hz, 6H, CH3), 0.81 (dd, 3JHP = 24.6 Hz, 3JHH = 12.3 Hz, 6H, CH3). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 143.2 (s, Ar-C), 134.1 (s, Ar-C), 122.8 (s, Ar-C), 68.4 (m, Ar-C), 29.8 (m) 27.1 (m), 23.6 (m), 22.8 (m), 19.6 (m), 19.4 (m), 19.1 (m), 18.8 (m). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 79.9 (d, 2JPP = 6 Hz, 1JPtP = 4615 Hz), 74.7 (d, 2JPP = 6 Hz, 1JPtP = 3068 Hz). Anal. Calcd for C45H36BF20P2Pt: C, 44.03; H, 3.20. Found: C, 44.14; H, 3.15. [(dippe)PtMe(OEt2)][BArf4] (4[BArf4]). A flask was charged with (dippe)PtMe2 (543 mg, 1.11 mmol) and [H(OEt2)2][BArf4] (1.078 g, 1.11 mmol; [CPh3][BArf4] may also be used). Upon addition of Et2O (15 mL), evolution of methane occurred. The reaction was stirred at ambient temperature for 90 min, and then the solvent removed under

Figure 2. Solid-state molecular structure of [(dippe)Pt(μSbHMes)]22+ (11+). Thermal ellipsoids are shown at the 35% probability level. Hydrogen atoms are omitted for clarity.

There have been several studies to understand the ligand effects of tertiary stibines for platinum and other metals.58−60 However, investigations of stibido (R2Sb−) ligands has been much less common, and a limited number of structurally characterized complexes are known.61−63 A structurally characterized complex with a stiba-dionate ligand, (Et3P)2PtCl{Sb[C(O)Mes]2}, reported by Jones and coworkers has Pt−Sb = 2.6042(4) Å, which is comparable to the Pt−Sb bond length of 11.61,62 The formation of dimers 11 and 12 rather than the α-H migration products [(dippe)Pt(H)SbR]+ (R = Mes, dmp) may reflect a diminished ability of the SbR unit to stabilize a partial positive charge. By comparison to the [(dippe)Pt(H) EMes2]+ series (E = Si, Ge, Sn) which possess electrophilic E centers, 1,3 the hypothetical complex “[(dippe)Pt(H) SbMes]+” might similarly create an electrophilic SbR group, which is presumably unstable.

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CONCLUSIONS Two cationic platinum methyl complexes [(dippe)PtMe(OEt2)][A] (4+; [A] = B(C6F5)4, BArf4) stand out in a family of related species as readily prepared and highly reactive. These complexes engage in silylene extrusion, as demonstrated by reaction of 4[BArf4] with Mes2SiH2 to give [(dippe)Pt(H) SiMes2]+. Extrusion reactions of the heavier group 14 elements have also been demonstrated in preparation of [(dippe)Pt(H)GeMes2]+ and [(dippe)Pt(H)SnMes2]+ by reaction of 4[BArf4] with Mes2GeH2 and Mes2SnH2, respectively. Importantly, the synthesis of these [(dippe)Pt(H)EMes2]+ complexes from 4+ does not require the use of a methyl abstractor (e.g., B(C6F5)3) to generate the desired PtE bonds, thereby introducing an additional synthetic route through which these linkages can be accessed. The rich bond-activation chemistry of the [(dippe)PtMe(OEt2)]+ cation is also highlighted by its reactions with tertiary silanes, as well as with several primary stibines. Each of these E

DOI: 10.1021/acs.organomet.9b00097 Organometallics XXXX, XXX, XXX−XXX

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Organometallics reduced pressure. The residue was washed with hexanes (2 × 5 mL) and then extracted into Et2O (ca. 6 mL). The solution was filtered and 3 mL of pentane (3 mL) was layered on the filtered solution, which was then cooled to −35 °C to give colorless crystals in several crops (1.13 g, 0.802 mmol, 72%). Anal. Calcd for C51H37BF24OP2Pt: C, 44.08; H, 2.68. Found: C, 43.46; H, 2.76. [(dippe)PtMe(OEt2)][B(C6F5)4] (4[B(C6F5)4]). Prepared as above from (dippe)PtMe2 (420 mg, 0.862 mmol) and [CPh3][B(C6F5)4] (811 mg, 0.862 mmol) to afford colorless crystals (612 mg, 0.500 mmol, 58%). [(dippe)PtMe(PPh3)][B(C6F5)4] (5). A flask was charged with 4[B(C6F5)4] (75 mg, 0.061 mmol) and PPh3 (16 mg, 0.061 mmol). The solids were dissolved in 4 mL of CH2Cl2, and the resulting paleyellow solution was stirred at ambient temperature for 1 h. The solvent was removed under reduced pressure. The residue washed with hexanes (2 × 3 mL) and dissolved in Et2O (ca. 4 mL), and then the solution was filtered. Pentane (ca. 2 mL) was layered on the solution, and upon cooling for at least 3 d, colorless crystals of the title complex were obtained (80 mg, 0.054 mmol, 90%). 1H NMR (CD2Cl2, 400 MHz): δ 7.62−7.49 (m, 15H, Ar-H), 2.63 (m, 2H, CH), 1.88 (m, 4H, CH2), 1.32 (dd, 6H, CH3), 1.26 (m, 2H, CH), 0.99 (m, 12H, CH3), 0.439 (pseudodt, CH3, 3JHP = 11.2, 8.0 Hz, 2JPtH = 55.4 Hz, 3H). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 135.6 (br s, Ar-C), 131.9 (s, Ar-C), 129.4 (d, JPC = 6 Hz, Ar-C), 117.8 (m, Ar-C), 25.2 (m), 25.0 (m), 21.3 (d, JPC = 6 Hz, CH3), 19.2 (br s, CH3), 18.0 (br s, CH3), 17.7 (d, CH3, JPC = 7 Hz), −2.7 (m, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 72.9 (dd, 2JPP = 15.5, 6.0 Hz, 1JPtP = 1815 Hz), 71.5 (dd, 2JPP = 35.7, 6.0 Hz, 1JPtP = 2701 Hz), 25.72 (dd, 2JPP = 35.7, 15.5 Hz, 1JPtP = 2676 Hz). IR (Nujol, KBr): 1604 s, 1566 m, 1405 s, 1334 w, 1250 s, 1238 s, 1158 m, 1136 m, 1114 m, 1108 m, 1084 s, 1024 s, 960 w, 953 m, 887 s, 855 w, 798 m, 787 s, 730 w, 694 s, 685 s, 645 s, 634 m, 618 s, 524 w, 510 w, 489 m, 468 m, 450 w, 424 w, 404 w cm−1. Anal. Calcd for C57H50BF20P3Pt: C, 48.41; H, 3.57. Found: C, 48.43; H, 3.73. [(dippe)PtMe{cyclo-Si(NtBuCH)2}][B(C6F5)4] (6). [(dippe)PtMe{cyclo-Si(NtBuCH)2}][B(C6F5)4] (6) was prepared similarly to 5 from 4[B(C6F5)4] (85 mg, 0.069 mmol) and cyclo-Si(NtBuCH)2 (14 mg, 0.069 mmol) to afford colorless crystals (70 mg, 0.052 mmol, 75%). 1H NMR (CD2Cl2, 400 MHz): δ 6.81 (br s, 2H, CH), 2.56 (m, 2H, CH), 2.29 (m, 2H, CH), 1.99 (m, 4H, CH2), 1.47 (s, 18H, CH3) 1.14 (m, 24H, CH3), 0.97 (dd, 3JHP = 12.9, 8.0 Hz, 2JPtH = 59.2 Hz, 3H, CH3). 13 C{1H} NMR (CD2Cl2, 101 MHz): δ 121.7 (s, CH), 56.6 (s, NC), 33.9 (s, CH3), 27.7 (m), 25.9 (m), 21.6 (br s, CH3), 20.6 (br s, CH3), 19.6 (br s, CH3), 19.5 (br s, CH3), −2.3 (m, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 82.78 (dd, 2JPP = 5.6 Hz, 1JPtP = 1853 Hz), 78.28 (dd, 2JPP = 5.6 Hz, 1JPtP = 2459 Hz). IR (Nujol, KBr): 1631 m, 1564 m, 1406 s, 1336 w, 1251 s, 1236 s, 1158 m, 1136 m, 1110 m, 1084 s, 1024 s, 950 m, 887 s, 787 s, 730 w, 684 s, 647 s, 638 m, 611 s, 520 w, 516 w, 488 m, 468 m, 404 w cm−1. Anal. Calcd for C49H55N2BF20P2PtSi: C, 43.62; H, 4.12; N, 2.08. Found: C, 43.84; H, 4.06; N, 1.94. [(dippe)PtMe(2,6-(CH3)2NC5H3)][B(C6F5)4] (7). [(dippe)PtMe(2,6-(CH3)2NC5H3)][B(C6F5)4] (7) was prepared similarly to 5 from 4[B(C6F5)4] (85 mg, 0.069 mmol) and 2,6-lutidine (7 mg, 0.069 mmol) to afford colorless crystals (74 mg, 0.059 mmol, 81%). 1H NMR (CD2Cl2, 400 MHz): δ 7.72−7.11 (m, 23H, Ar-H), 2.51 (s, 6H, CH3), 1.30 (m, 4H, CH2), 0.43 (dd, 3JPH = 6.8, 6.4 Hz, 2JPtH = 49.6 Hz, 3H, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 46.7 (br s, 1JPtP = 1741 Hz), 34.8 (br s, 1JPtP = 3825 Hz). IR (Nujol, KBr): 1648 s, 1554 m, 1487 s, 1414 s, 1338 w, 1242 s, 1231 s, 1158 m, 1136 m, 1114 m, 1088 s, 1024 s, 957 m, 882 s, 778 s, 732 w, 685 s, 645 w, 638 m, 616 s, 524 w, 522 w, 464 m, 422 m, 404 w cm−1. Anal. Calcd for C58H36NBF20P2Pt: C, 49.95; H, 2.60; N, 1.00. Found: C, 50.08; H, 2.31; N, 1.24. [(dippe)Pt(H)SiMes2][BArf4] (1[BArf4]). A flask was charged with 4[BArf4] (133 mg, 0.0943 mmol) and dissolved in 5 mL of CH2Cl2. The solution was cooled to −35 °C, and a cold CH2Cl2 solution of Mes2SiH2 (25 mg, 0.0931 mmol) was added. The yellow solution was stirred at ambient temperature for 2.5 h, and then the solvent was removed under reduced pressure. The residue was washed with hexanes (2 × 3 mL) and redissolved in minimal Et2O, and the solution was filtered. Pentane (∼2 mL) was layered on the solution and upon cooling, a yellow powder of 1[BArf4] was obtained (75 mg, 0.0472

mmol, 50%). 1H and 31P{1H} NMR spectroscopic properties of 1[BArf4] are identical to those reported for the corresponding −MeB(C6F5)3 salt.14 [(dippe)Pt(H)SiMes 2 (DMAP)][BAr f 4 ] (1[BAr f 4 ]·DMAP). A Schlenk flask was charged with 4[BArf4] (162 mg, 0.115 mmol) and Mes2SiH2 (31 mg, 0.115 mmol) and attached to a 180° joint. The apparatus was evacuated, and ca. 8 mL of CH2Cl2 was vacuumtransferred into the Schlenk flask at −78 °C. The resulting solution was warmed to −30 °C becoming bright yellow and evolving gas. At that temperature, DMAP (14 mg, 0.115 mmol) in a 5 mL of CH2Cl2 solution was added via a cannula. The solution was gradually warmed to ambient temperature and stirred for an additional 4 h. The solvent was then removed under reduced pressure. The residue washed with hexanes (2 × 3 mL) and redissolved in CH2Cl2 (6 mL), and the solution was filtered. Pentane (ca. 3 mL) was layered on the solution, and upon cooling, pale yellow crystals of 1[BArf4]·DMAP were obtained in several crops (97 mg, 0.061 mmol, 53%). Spectroscopic data were identical to an authentic sample prepared by the literature method.14 [(dippe)Pt(H)GeMes2][BArf4] (8). A flask was charged with 4[BArf4] (210 mg, 0.149 mmol) and dissolved in 7 mL of CH2Cl2. The solution was cooled to −35 °C, and a cold CH2Cl2 solution of Mes2GeH2 (47 mg, 0.149 mmol) was added. The lemon-yellow solution was stirred at ambient temperature for 2.5 h, and then the solvent was removed under reduced pressure. The residue was washed with hexanes (2 × 3 mL) and redissolved in minimal CH2Cl2, and the solution was filtered. Pentane (∼2 mL) was layered on the solution, and upon cooling, canary yellow crystals of 8 were obtained (173 mg, 0.106 mmol, 71%). 1H NMR (CD2Cl2, 400 MHz): δ 6.98 (s, 4H, C6H2Me2), 2.39 (s, 12H, CH3), 2.30 (s, 6H, CH3), 2.22 (m, 4H, CHMe2), 1.99 (m, 4H, CH2), 1.22 (dd, 3JHP = 17.6 Hz, 3JHH = 7.2 Hz, 6H, CH3), 1.15 (dd, 3 JHP = 10.4 Hz, 3JHH = 7.2 Hz, 6H, CH3), 1.08 (dd, 3JHP = 13.2 Hz, 3JHH = 8.4 Hz, 6H, CH3), 0.88 (dd, 6H, 3JHP = 6.8 Hz, 3JHH = 5.6 Hz, CH3), −2.26 (dd, 1JHP = 109.2, 5.6 Hz, 1JPtH = 995.2 Hz, 1H, PtH). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 153.2 (d, JPC = 13.9 Hz, Ar-C), 143.2 (s, Ar-C), 135.3 (s, Ar-C), 129.8 (s, Ar-C), 26.8 (m, CHMe2), 23.9 (s, CH3), 22.9 (m, CH2), 21.4 (s, CH3), 19.8 (d, JPC = 2 Hz, JPtC = 18.1 Hz, CH3), 19.4 (d, JPC = 2.5 Hz, JPtC = 18.3 Hz, CH3), 18.9 (d, JPC = 1.5 Hz, JPtC = 19.2 Hz, CH3), 18.2 (d, JPC = 1.8 Hz, JPtC = 19.1 Hz, CH3). 31 1 P{ H} NMR (CD2Cl2, 161.97 MHz): δ 91.5 (d, 2JPP = 3 Hz, 1JPPt = 2326 Hz), 91.0 (br s, 1JPPt = 2326 Hz). IR (Nujol, KBr): 1609 s, 1564 m, 1408 s, 1336 w, 1251 s, 1237 s, 1158 m, 1134 m, 1110 m, 1106 m, 1086 s, 1080 s, 1024 s, 961 w, 953 m, 887 s, 855 w, 798 m, 787 s, 730 w, 694 s, 685 s, 645 s, 631 m, 615 s, 520 w, 512 w, 487 m, 466 m, 451 w, 423 w, 418 m, 404 w cm−1. Anal. Calcd for C64H63BF24GeP2Pt: C, 47.20; H, 3.90. Found: C, 47.36; H, 4.15. [(dippe)Pt(H)SnMes2][BArf4] (9). A flask was charged with 4[BArf4] (280 mg, 0.199 mmol) and dissolved in 8 mL of CH2Cl2. The solution was cooled to −35 °C, and a cold CH2Cl2 solution of Mes2SnH2 (71 mg, 0.199 mmol) was added in the dark. The maroon solution was stirred at ambient temperature for 2.5 h, and then the solvent was removed under reduced pressure. The residue was washed with hexanes (2 × 3 mL) and redissolved in minimal CH2Cl2, and the solution was filtered. Drying the CH2Cl2 solution gave an orange-red foam of 9 (113 mg, 0.067 mmol, 34%). 1H NMR (CD2Cl2, 400 MHz): δ 6.76 (s, 4H, C6H2Me2), 2.20 (s, 12H, CH3), 1.87 (s, 6H, CH3), 1.63 (m, 4H, CHMe2), 1.53 (m, 4H, CH2), 1.00−0.81 (m, 24H, CH3), −2.72 (dd, 2JPH = 121.4, 5.4 Hz, 1JPtH = 968.3 Hz, 1H, PtH). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 151.7 (d, JPC = 13.9 Hz, Ar-C), 141.6 (s, Ar-C), 134.4 (s, Ar-C), 129.6 (s, Ar-C), 25.3 (m, CHMe2), 23.8 (s, CH3), 22.3 (m, CH2), 21.4 (s, CH3), 20.1 (br s, CH3), 19.6 (br s, CH3), 18.6 (br s, CH3), 17.8 (br s, CH3). 31P{1H} (CD2Cl2, 162 MHz): δ 88.9 (br s, 1JPPt = 2302 Hz), 87.3 (d, 1JPP = 4 Hz, JPPt = 2274 Hz). Repeated attempts did not provide satisfactory elemental analysis. [(dippe)Pt(μ-H)]2[BArf4]2 (10). A 50 mL round bottom flask was charged with [(dippe)PtH]2 (410 mg, 0.399 mmol), and the solid was dissolved in 10 mL of tetrahydrofuran (THF). The resulting solution was cooled to −30 °C, and a cold 8 mL THF slurry of [Cp2Fe][BArf4] (838 mg, 0.799 mmol) was added. The color immediately changed from blue to orange yellow. After 1 h of stirring, the solvent was removed under reduced pressure. The residual was washed with F

DOI: 10.1021/acs.organomet.9b00097 Organometallics XXXX, XXX, XXX−XXX

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hexanes (3 × 10 mL) and then extracted into ca. 20 mL of Et2O. The solution was filtered, and ca. 15 mL pentane layered on the solution. The mixture was cooled to −30 °C for 4 d to give yellow crystals (835 mg, 0.303 mmol, 76%). 1H NMR (CD2Cl2, 400 MHz): δ 2.18 (m, 4H, CH2), 1.85 (m, 4H, CH), 1.16 (m, 24H, CH3), −2.86 (pseudo-quintet, 2 JPH = 47 Hz, 1JPtH = 483 Hz, 1H, Pt−H). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 24.6 (m, CH2), 21.4 (m, CH), 19.6 (m, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 104.3 (2nd-order multiplet,18 JPP = 62.1 Hz, JPPt = 2830, 149 Hz). IR (Nujol, KBr): 1923 s, 1560 m, 1412 s, 1334 w, 1250 s, 1238 s, 1156 m, 1134 m, 1108 m, 1088 s, 1081 s, 1024 s, 960 w, 958 m, 889 s, 857 w, 792 m, 781 s, 730 w, 692 s, 646 s, 630 m, 601 s, 528 w, 514 w, 486 m, 456 m, 448 w, 424 w, 416 m, 404 w cm−1. Anal. Calcd for C92H90B2F48P4Pt2: C, 41.80; H, 3.43. Found: C, 41.23; H, 3.35. [(dippe)Pt(μ-SbHMes)]2[BArf4]2 (11). A Schlenk flask was charged with 10 (143 mg, 0.054 mmol), and the platinum complex was dissolved in 4 mL of CH2Cl2. A solution of MesSbH2 (26 mg, 0.108 mmol) in 3 mL of CH2Cl2 was added resulting in immediate gas evolution. The yellow solution was stirred at ambient temperature for 20 min before the solvent was removed under reduced pressure. The residue was washed with hexanes (3 mL) and dissolved in CH2Cl2 (ca. 4 mL), and then the solution was filtered. Pentane (ca. 2 mL) was layered on the solution, and upon cooling to −30 °C, pale yellow X-ray quality crystals were obtained (43 mg, 0.015 mmol, 27%). 1H NMR (CD2Cl2, 400 MHz): δ 7.02 (s, 2H, C6H2Me3), 3.20 (s, 3H, CH3), 2.47 (s, 3H, CH3), 2.35 (s, 3H, CH3), 1.87 (m, 4H, CH), 1.37 (dd, 3JHP = 13.6 Hz, 3 JHH = 6.8 Hz, 6H, CH3), 1.26 (m, 4H, CH2), 1.17 (dd, 3JHP = 18.8 Hz, 3 JHH = 7.2 Hz, 6H, CH3), 1.06 (dd, 3JHP = 15.6 Hz, 3JHH = 4.0 Hz, 6H, CH3), 0.43 (dd, 3JHH = 20.3 Hz, 3JHH = 10.8 Hz, 6H, CH3), −4.33 (tt, 3 JPH = 71.8, 5.2 Hz, 2JPtH = 442.3 Hz, 1H, SbH). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 146.7 (d, JPC = 13.9 Hz, Ar-C), 144.1 (s, Ar-C), 136.2 (s, Ar-C), 130.1 (s, Ar-C), 27.8 (m, CH), 23.6 (s, CH3), 22.1 (m, CH2), 21.3 (s, CH3), 19.6 (br s, CH3), 19.1 (br s, CH3), 18.5 (br s, CH3), 18.1 (br s, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 80.2 (br s, 1JPPt = 2419 Hz), 84.5 (br s, 1JPPt = 2761 Hz). IR (Nujol, KBr): 1824 m (νSbH), 1614 s, 1568 m, 1484 s, 1408 s, 1338 w, 1250 s, 1236 s, 1155 m, 1132 m, 1110 m, 1108 m, 1086 s, 1084 s, 1024 s, 960 w, 955 m, 884 s, 856 w, 785 s, 731 w, 696 s, 644 s, 630 m, 612 s, 530 w, 515 w, 488 m, 462 m, 450 w, 424 w, 404 w cm−1. Anal. Calcd for C110H110B2F48P4Pt2Sb2: C, 42.30; H, 3.55. Found: C, 42.47; H, 3.71. [(dippe)Pt(μ-SbHdmp)]2[BArf4]2 (12). A flask was charged with 10 (181 mg, 0.069 mmol) and 4 mL of CH2Cl2. A 3 mL CH2Cl2 solution of dmpSbH2 (30 mg, 0.069 mmol) was added resulting in immediate gas evolution. The resulting yellow solution was stirred at ambient temperature for 20 min. The solvent was removed under reduced pressure. The residue washed with hexanes (2 × 5 mL) and dissolved in CH2Cl2 (ca. 4 mL), and then the solution was filtered. Pentane (ca. 2 mL) was layered on the solution, and upon cooling to −30 °C, pale yellow crystals were obtained (134 mg, 0.043 mmol, 63%). 1H NMR (CD2Cl2, 400 MHz): δ 7.08 (s, 2H, C6H2Me3), 6.87 (s, 2H, C6H2Me3), 2.35 (s, 3H, CH3), 2.32 (m, 4H, CH), 2.19 (s, 6H, CH3), 2.17 (s, 3H, CH3), 1.95 (s, 6H, CH3), 1.49 (m, 4H, CH2), 1.28− 1.13 (m, 24H, CH3), −5.99 (tt, 3JPH = 70.6, 5.2 Hz, 2JPtH = 458.2 Hz, 1H, SbH). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 146.2 (s, Ar-C), 141.2 (d, JPC = 12.1 Hz, Ar-C), 140.7 (s, Ar-C), 136.6 (s, Ar-C), 134.1 (s, Ar-C), 131.6 (s, Ar-C), 128.9 (s, Ar-C), 127.1 (s, Ar-C), 24.8 (m, CHMe2), 24.2 (s, CH3), 23.7 (s, CH3), 22.4 (m, CH2), 21.5 (s, CH3), 21.3 (s, CH3), 20.1 (br s, CH3), 19.6 (br s, CH3), 18.7 (br s, CH3), 18.5 (br s, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 80.2 (br s, 1JPPt = 3432 Hz), 79.7 (br s, 1JPPt = 3032 Hz). IR (Nujol, KBr): 1828 m (νSbH), 1606 s, 1561 s, 1485 s, 1407 s, 1338 w, 1251 s, 1236 s, 1150 m, 1135 m, 1112 m, 1108 m, 1084 s, 1024 s, 962 w, 954 m, 889 s, 856 w, 783 s, 730 w, 696 s, 631 m, 610 s, 534 w, 489 m, 461 m, 454 w, 424 w cm−1. Anal. Calcd for C140H138 B2F48P4Pt2Sb2: C, 47.88; H, 3.96. Found: C, 47.98; H, 3.74.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.9b00097. Details of X-ray crystallography; DFT calculations; and1H NMR spectra of all new compounds (PDF) Atomic coordinates of 1* (XYZ) Atomic coordinates of 8* (XYZ) Atomic coordinates of 9* (XYZ) Accession Codes

CCDC 1897093 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_ [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Rory Waterman: 0000-0001-8761-8759 Rex C. Handford: 0000-0002-3693-1697 T. Don Tilley: 0000-0002-6671-9099 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the U.S. National Science Foundation under grant no. CHE-1566538 and the Miller Institute for Basic Research in Science through a Research Fellowship (R.W.). The authors thank Professor David Milstein for insightful discussions, Dr. David Small for his assistance in the computations, and Dr. Nathan R. Neale for the preparation of Mes2SnH2. Calculations were performed on the Tiger cluster of the UC Berkeley Molecular Graphics and Computation Facility (MGCF), which is funded by the U.S. National Institutes of Health under grant no. NIH S10OD023532.

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REFERENCES

(1) Waterman, R.; Hayes, P. G.; Tilley, T. D. Synthetic Development and Chemical Reactivity of Transition-Metal Silylene Complexes. Acc. Chem. Res. 2007, 40, 712−719. (2) Fasulo, M. E.; Lipke, M. C.; Tilley, T. D. Structural and Mechanistic Investigation of a Cationic Hydrogen-Substituted Ruthenium Silylene Catalyst for Alkene Hydrosilation. Chem. Sci. 2013, 4, 3882. (3) Lipke, M. C.; Liberman-Martin, A. L.; Tilley, T. D. Electrophilic Activation of Silicon-Hydrogen Bonds in Catalytic Hydrosilations. Angew. Chem., Int. Ed. 2017, 56, 2260−2294. (4) Smith, P. W.; Tilley, T. D. Base-Free Iron Hydrosilylene Complexes via an α-Hydride Migration that Induces Spin Pairing. J. Am. Chem. Soc. 2018, 140, 3880−3883. (5) Grumbine, S. K.; Tilley, T. D. Transition-Metal-Mediated Redistribution at Silicon: A Bimolecular Mechanism Involving Silylene Complexes. J. Am. Chem. Soc. 1994, 116, 6951−6952. (6) Corey, J. Y. Dehydrocoupling of Hydrosilanes to Polysilanes and Silicon Oligomers: A 30 Year Overview. Advances in Organometallic Chemistry; Elsevier, 2004; Vol. 51, pp 1−52. (7) Toal, S. J.; Sohn, H.; Zakarov, L. N.; Kassel, W. S.; Golen, J. A.; Rheingold, A. L.; Trogler, W. C. Syntheses of Oligometalloles by Catalytic Dehydrocoupling. Organometallics 2005, 24, 3081−3087.

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DOI: 10.1021/acs.organomet.9b00097 Organometallics XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.organomet.9b00097 Organometallics XXXX, XXX, XXX−XXX