Planar PtPd 3 Complexes Stabilized by Three Bridging Silylene Ligands

A heterobimetallic PtPd 3 complex supported by three bridging diphenylsilylene ligands, [Pt{Pd(dmpe)} 3 (μ 3 ‐SiPh 2 ) 3 ] ( 1 , dmpe=1,2‐bis(dimethylphosphino)ethane), has been synthesized from mononuclear Pd and Pt complexes. The hexagonal core composed of Pt, Pd, and Si atoms is slightly larger than that of the tetrapalladium complex, [Pd{Pd(dmpe)} 3 (μ 3 ‐SiPh 2 ) 3 ] ( 2 ). Reaction of PhSiH 3 with complex 1 in the presence and absence of Ph 2 SiH 2 results in the formation of a tetranuclear complex with silyl and hydride ligands at the Pt center, [PtH(SiPh 2 H){Pd(dmpe)} 3 (μ 3 ‐SiHPh) 3 ] ( 3 ), and an octanuclear complex, [{Pt{Pd(dmpe)} 3 (μ 3 ‐SiHPh) 3 } 2 (κ 2 ‐dmpe)] ( 5 ), respectively. Both M−Si (M=Pt, Pd) bond lengths and the 29 Si NMR chemical shifts of 1 and 2 are located between those of mononuclear late transition‐metal complexes with a silylene ligand and complexes with donor‐stabilized silylene ligands. CuI and AgI adducts of 1 and 2 , formulated as [M(μ‐M′I){Pd(dmpe)} 3 (μ 3 ‐SiPh 2 ) 3 ] (M=Pt, Pd; M′=Cu, Ag), undergo elimination of CuI (AgI) and regenerate the tetrametallic complexes upon heating or addition of a chelating diphosphine. Elimination of AgI from 2‐AgI occurs more rapidly than elimination of CuI from 2‐CuI , as determined from the results of kinetics experiments.