Interconversions of the silylene-to-silene and germylene-to-germene types: direct spectroscopic studies and calculations

The recent advances in spectroscopic and quantum-chemical studies of carbene-to-olefin isomerization of carbene analogs of Group 14 elements are discussed. Primary attention is devoted to the use of matrix isolation spectroscopy, whose successful combination with modern calculation techniques has resulted in the first spectroscopic characterization of a number of novel short-lived silylenes and germylenes and their structural isomers with unsaturated Si=C, Ge=C, and Si=O bonds.