Competitive Molecular Rearrangements in Hexacoordinate Cyano-Silicon Dichelates

Pentacoordinate siliconium chloride or neutral hexacoordinate silicon complexes with imino-nitrogen donor groups react with cyanotrimethylsilane in two competing reactions, leading either to addition of the cyano group to the imino carbon or to hexacoordinate cyano-silicon complexes. The latter may further transform to a rearranged tricyclic pentacoordinate complex. The common driving force for these reactions seems to be the conversion of one of the two initial N→Si dative bonds, present in the starting complexes, to a shorter formal covalent bond.