The Silicon Version of Phosphine Chalcogenides: Synthesis and Bonding Analysis of Stabilized Heavy Silaaldehydes

The synthesis of chalcogena-silaaldehydes (Ch = S, Se, Te), 15, stabilized by interaction with N-heterocylic carbenes (NHCs) is reported. Compounds 15 are formed by reaction of the NHC-stabilized hydridosilylene 13a with elemental chalcogens in moderate yields. X-ray diffraction analysis of all three variants of the chalcogena-silaaldehydes, 15, revealed short Si/Ch distances which are close to expected values for SiCh double bonds. The results of natural bond orbital and natural resonance theory analyses indicate strongly polarized Si–Ch bonds and suggest the occurrence of negative hyperconjugation, which is responsible for the short Si/Ch distances. These results indicate the isolobal relation between NHC-stabilized heavy silaaldehydes 15 and the well-known phosphine chalcogenides, R₃PCh.