Thermolysis Reactions ofcis-PtR(SiPh₃)(PMe₂Ph)₂in Solution

A series of trans - and cis -PtR(SiPh 3 )(PMe 2 Ph) 2 complexes have been prepared and their thermolysis reactions in solution examined. The trans isomers (R = Me, Et) are robust, and only the methyl complex affords MeSiPh 3 as the reductive elimination product in 72−82% yields. In contrast, the cis isomers (R = Me, Et, Pr, Bu) form the corresponding alkylsilanes in almost quantitative yields (>97%). Despite the selective formation of the reductive elimination products, the cis -alkyl−silyl complexes bearing β-hydrogens undergo a rapid repetition of the β-hydrogen elimination and insertion processes, as confirmed by a deuterium-labeling experiment using cis -Pt(CH 2 CD 3 )(SiPh 3 )(PMe 2 Ph) 2 . The alkylsilane formation from the cis isomers proceeds via two reaction paths. One is the direct C−Si reductive elimination. On the other path, the cis -PtR(SiPh 3 )(PMe 2 Ph) 2 complexes are initially isomerized to the corresponding cis -PtPh(SiRPh 2 )(PMe 2 Ph) 2 complexes by the exchange of the Pt−R group with the Si−Ph group, and the resulting phenyl−silyl complexes reductively eliminate alkylsilanes. The methyl−silyl complex decomposes exclusively by the former path, while the other alkyl−silyl complexes (R = Et, Pr, Bu) follow mainly the latter path. Preparation and thermolysis reaction of the related cis -PtEt(GePh 3 )(PMe 2 Ph) 2 are also reported.