Planar Tetranuclear and Dumbbell-Shaped Octanuclear Palladium Complexes with Bridging Silylene Ligands

摘要

Late-transition-metal complexes with silylene (SiR2) ligands have attracted considerable attention since the proposal of platinum-silylene intermediates in the [PtCl2(PEt3)2]-cata-lyzed reactions that convert organodisilanes into oligosilanes and the cyclic adducts into alkynes. Mononuclear silylene complexes of platinum and other late transition metals were not isolated until some years later, probably because of the extremely high reactivity of most M=Si double bonds. Dinuclear complexes of late transition metals with bridging silylene ligands are more common. The dinuclear platinum complex [{Pt(PR3)}2(μ-SiHPh2)2] (PR3 = PPh3, PCy3 etc.) has been reported. However, in spite of the stable coordination of bridging silylene ligands, complexes containing three or more metal atoms with bridging Si ligands have few precedents, and those known are stabilized by electron-withdrawing CO and CNR ligands. Braddock-Wilking and coworkers and our group have reported zero-valent triangular Pt3 complexes, stabilized by bridging silylene and phosphine ligands. Chen, Shimada, and Tanaka employed 1,2-disilabenzene as a ligand and prepared trinuclear Pd complexes supported by the Si ligands.