Rearrangements of alkyne and 1,3-diyne in transition metal center forming small ring complexes

The rearrangement of the linear alkynes(s) and 1,3-diyne(s) in transition metal center has recently lead to the isolations of small ring organometallics constituted of unsaturated carbon atoms. Four-membered 1-metallacyclo-2-butene and MCp compounds with a MC4-unit reveal a diverse array of bond multiplicity that undergoes complexation. Recently explored angular phenylene compounds of cobaltacene, and metallapentalene are also described.