Development of Novel Transformation Reactions of Silicon Compounds Utilizing Specific Reactivity of Transition Metal-Silylene Complexes

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Through the mechanistic studies using silyl(silylene) complexes stabilized by bulky mesityl groups, we proved that the 1,3-migration of a substituent from the silyl ligand to the silylene ligand and the 1,2-migration of the silyl ligand from the metal to the silylene ligand proceed reversibly under mild conditions. We also found that an aryl ligand migrates reversibly between a metal center and a silylene ligand in some tungsten complexes. With the help of steric protection of a bulky alkyl group, we synthesized and stabilized a silylenetungsten complex having a hydrogen on the silylene ligand, and succeeded in determining the crystal structure for the first time for this type of complex. This crystal structure analysis revealed that a hydride ligand bridges over the tungsten-silicon double bond. This hydrosilylene complex was found to react with various polar organic molecules such as nitriles, ketones, enones, and methanol to give the products formed through hydrosilylation, [4+2] cy … More cloaddition, etc. By these researches, we demonstrated that, on several silylene complexes, the metal-silicon double bond plays an important role to induce specific interactions and rearrangements, and causes new types of chemical conversions on silicon compounds.Three-membered metallacycles composed of silicon, phosphorus, and iron were first synthesized, and the structure, rearrangement reaction, dimerization reaction, and reactions with various polar molecules were investigated. These reactions all proceeded accompanied by the cleavage of the silicon-phosphorus bond, probably because, in these metallacycles, contribution of the canonical form of phosphide(silylene) complex is substantial and causes strong polarization of the silicon-phosphorus bond, and also the ring strain activates the bond. An analogous formation and reactions of metallacycles were also observed in the systems containing sulfur or tellurium instead of phosphorus, whereas in the system containing nitrogen, an interesting reaction involving migration of the aminosilyl ligand onto a negative atom was found to occur. Less