Construction of Novel Silicon-Transition Metal Multiple Bonds, Elucidation of the Mechanisms for Their Reactions, and Their Expansion to Catalytic Reactions

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By a newly developed method, we succeeded in synthesizing the first hydrido (hydrosilylene) ruthenium complex. This complex reacted readily with aldehydes, nitriles, and alkyne to give agostic complexes selectively as primary products. These products are presumed to form through [2+2] cycloaddition between the Ru=Si bond and unsaturated bonds of the substrates followed by partial reductive elimination of the Si-H bond. The complex also reacted smoothly with enones, isocyanates, isothiocyanates, etc. to afford complexes with intriguing structures through [4+2] cycloaddition, hydride migration, C=S bond cleavage, etc.We also succeeded in the synthesis of base-free silyl (silylene) ruthenium complex, and revealed its structure and dynamic behavior. This complex is more reactive than the iron analogue, and addition of a strong Lewis base DMAP resulted in formation of a base-stabilized silyl (silylene) complex was converted to an unprecedented η^<4->sila-o-quinodimethane complex. Moreover, … More the reaction of the silyl (silylene) complex with alcohol surprisingly induced the substitution of all methyl groups on the silyl ligand with alkoxy groups to produce a trialkoxysilyl complex.We demonstrated that the tungsten complexes with an aryl ligand and a silylene ligand underwent 1, 2-aryl migration from the tungsten center to the silylene ligand through formation of η^<3->-silabenzyl complexes as intermediates. The coordinatively unsaturated silyl complexes generated by this migration reacted with nitriles to yield K^<2-> iminoacyl complexes through insertion of a nitrile molecule into the tungsten-silicon bond. The K^<2-> iminoacyl complexes further reacted with another molecule of nitrile to give five-membered metallacycles through ring expansion.By the reaction of a bis (phosphine) platinum complex with sterically congested tribromosilane in the presence of a reducing agent, we succeeded in synthesizing the first (bromosilylene) platinum complex. X-ray crystal structure analysis revealed that this complex has a very short platinum-silicon bond and a completely planar tricoordinate silicon. These facts clearly demonstrate the double bond character of the platinum-silicon boon. We also succeeded in derivation of this complex to a base-stabilized cationic silylyne complex. Less