Synthesis of Stable Silylene and Germylene Complexes and the Mechanistic Studies on Catalytic Reactions Utilizing Them

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(1) Using tungsten as a central metal, donor-bridged bis(silylene) complexes, external donor-stabilized silyl(silylene) complexes, dimeric silyl(silylene) complexes in which the oxygen atoms of carbonyl ligands are mutually coordinated to the silylene ligands to form an eight-membered ring, and donor-free germyl(germylene) complexes were synthesized by photolysis of carbonyl complexes. The structures of these complexes have been determined by X-ray crystallography. 1,3-Migration of substituents was demonstrated to occur on isolated silyl(silylene) complexes.(2) Reactivity of bis(silylene)ruthenium complexes was studied, and high electrophilicity of silylene ligands was proved based on their high reactivity toward alcohols and water, and the intramolecular C-H bond activation by the Si-Ru double bond. Dimethylsilylene was found to add to bis(silylene)ruthenium and iron complexes to give disilanyl(silylene) complexes.(3) By means of iridium complexes having a (phosphinoethyl)silyl ligand, we found the following new reactions ; redistribution of substituents on hydrodisilanes, formation of SiR(Me)H2 by transfer of a methyl group from a methyl(hydrido)iridium complex to RSiH3, formation of a hydrido(silylene) complex via 1,2-hydrogen sift from a hydrosilyl ligand to a coordinatively unsaturated metal center, etc.(4) We newly prepared some donor-stabilized cationic germylene complexes and diiron and iron-tungsten complexes bridged by a secondary alkyl-substituted silylene ligand.(5) The first 1 , 2-phenylenedioxysilyl iron complex was synthesized, the structure determined, and the reactivity investigated.(6) As the new reactions of silyl(carbonyl)iron complexes, we found the reaction with LiAlH_4 leading the reduction of a CO ligand and coupling with a silyl group. to give a methylsilane, and the reaction with trialkylphosphites giving acyl complexes.