Recent advances in the chemistry of transition metal–silicon/germanium triple-bonded complexes

The chemistry of complexes bearing triple bonds between transition metals and silicon or germanium has made considerable progress in the last two decades. For base-free complexes of this type, neutral and cationic complexes of Groups 5, 6, 7, 8, and 10 transition metals are known so far. The synthetic routes for these complexes can be categorized into two patterns: (1) reactions starting from stable divalent Group 14 element species (Category I), and (2) reactions starting from tetravalent Group 14 element species (Category II). These synthetic reactions are described first, and then characteristic structures and spectroscopic properties are discussed. Finally, several unique reactions originating from the peculiar reactivity of the metal-silicon/germanium triple bonds of silylyne and germylyne complexes are presented.