Coupling reactions of manganese(I) cyclometallated compounds derived from heterocyclic N-donor ligands with alkynes

The reaction of PhCCPh with cyclomanganated compounds derived from substituted phenylimidazoles gave the seven-membered metallacycles [Mn{2-(CPhCPh)C6H4CNCHCHN(Me)}(CO)4] (1) and [Mn{2-(CPhCPh)C6H4CNCHN(Me)C(Ph)}(CO)4] (2), with insertion of the alkyne into the MnC bond. When an unsymmetrical alkyne such as MeCCPh was used, the reaction was not regiospecific and two different isomers were obtained, which could be separated by fractional crystallization, e.g. [Mn{2-(CMeCPh)C6H4CNCHN(Me)C(Ph)}(CO)4] (5) and [Mn{2-(CPhCMe)C6H4CNCHN(Me)C(Ph)}(CO)4] (6). The compounds were characterized by analytical and spectroscopic techniques, and in the case of 5, by X-ray crystallography.