The chemistry of organo(silyl)platinum(II) complexes relevant to catalysis

A variety of silylplatinum complexes cis- and trans-PtR(SiYPh2)L-2 (R = Me, Pt, Pr, Bu, vinyl, phenyl, phenylethynyl; Y = Ph, Me, H, F, OMe; L = PMePh 2, PMe2Ph), cis-Pt(SiR3)(SnMe3)(PMe2Ph)(2) (SiR3=SiMe3, SiMe2Ph, SiMePh2, S iPh3), and cis-Pt(SiR3)(2)(PMe2Ph)(2) (SiR3 = SiMe2Ph, SiMePh2, SiPh3) have been prepared, and their structures and reactivities toward C-Si bond form ation and phenylacetylene insertion have been examined by X-ray diffraction analysis, NMR spectroscopy, and kinetic experiments. Three types of proces ses are operative for C-Si bond formation from cis-PtR(SiYPh2)L-2 complexes giving RSiYPh2. One is the direct C-Si reductive elimination; most of the complexes follow this process. The second type involves isomerization of ci s-PtR(SiYPh2)L-2 to cis-PtY(SiRPh2)L-2, followed by Y-Si reductive eliminat ion; this process has been observed for cis-PtR(SiPh3)L-2 (R = Et, Pr, Bu) and cis-PtR(SiHPh2)L-2 (R = Me, Et, Pr, Bu). Reactions of alkyl-silyl compl exes with hydrosilanes also afford the corresponding alkylsilanes quantitat ively, constituting the third type of process. Insertion of phenylacetylene into the Pt-Si bond of PtR(SiPh3)L-2 complexes takes place only for the ci s isomers. Silyl-stannyl complexes undergo competitive insertion of phenyla cetylene into the Pt-Si and Pt-Sn bonds under kinetic conditions, whereas t he insertion into the Pt-Si bond predominates under thermodynamic condition s. Reactivities of four PtSiR3 bonds toward insertion relative to the Pt-Sn Me3 bond have been evaluated: SiMe3 ( > 49) > SiMe2Ph (1.9) > SiMePh2 (0.69 ) > SiPh3 (0.075). Bis-silyl complexes exhibit a rather intricate dependenc e of the insertion reactivity upon the sorts of silyl ligands, not simply c orrelated with the reactivity of Pt-SiR3 bonds, owing to the insertion proc ess involving prior dissociation of a phosphine ligand. The bis-silyl compl exes have a twisted square planar structure significantly distorted from pl anarity, and the rate of phosphine dissociation is highly sensitive to this distortion. (C) 2000 Elsevier Science S.A. All rights reserved.