Metal vinylidenes as catalytic species in organic reactions.

Organic vinylidene species have found limited use in organic synthesis owing to their inaccessibility. In contrast, metal vinylidenes are much more stable and may be readily accessed through transition-metal activation of terminal alkynes. These electrophilic species may be trapped by a number of nucleophiles. Additionally, metal vinylidenes can participate in pericyclic reactions and processes that involve migration of a metal ligand to the vinylidene species. This Focus Review addresses the reactions and applications of metal vinylidenes in organic synthesis.