Facile synthesis of transition metal complexes with five coplanar metal-carbon σ-bonds

Carbon is one of the most important elements in chemistry, forming a vast number of organic compounds.It can also form a variety of organometallic compounds with a metal-carbon bond.Metal alkyl, carbene and carbyne complexes are classical examples of organometallic compounds.A particularly interesting class of organometallic compounds are all-carbon metallacycles formed by combination of a metal and a hydrocarbon chain serving as a chelating agent with only carbon atoms as the donor atoms.