Photo-Driven Si-C Bond Cleavage in Hexacoordinate Silicon Complexes

Hexacoordinate diorganosilicon complexes of the type (ONNO)SiRR′, with (ONNO) being a di‐anionic salen‐type Schiff base ligand, were shown to undergo Si–C bond cleavage and intramolecular rearrangement (1,3‐shift of R’ to a former imine carbon atom) upon irradiation with UV. The course of this reaction depends on the nature of silicon‐bound substituents: Whereas complexes (ONNO)SiMe2 and (ONNO)SiPh2 give rise to the rearrangement of a methyl and a phenyl group, respectively, complexes of the type (ONNO)Si(aryl)(alkyl) were found to undergo Si–C(alkyl) bond cleavage exclusively.Furthermore, such alkyl groups bearing β‐hydrogen atoms may lead to β‐hydride transfer to the imine carbon atom accompanied by olefin elimination. Irradiation of compounds (ONNO)SiRX, with X being a non‐carbon sacrificial ligand, was shown to give rise to further side reactions: In case of X = F the unexpected formation of (ONNO)SiF2 was observed. In analogy to the photo‐induced rearrangement of (ONNO)SiPh2 the heavier congenor (ONNO)GePh2 exhibits similar behavior, whereas the related tin compound (ONNO)SnPh2 proved inert under these reaction conditions applied.