Dissolution of M(CO)(3)(Br)(L-Ar) [L-Ar = (2,6-Cl-2-C6H3-NCMe)(2)CH2] in either acetonitrile [M = Mn, Re] or benzonitrile (M = Re) results in C-C coupling of the nitrile to the diimine ligand. When reacted with acetonitrile, the intermediate adduct [M(CO)(3)(NCCH3)(L-Ar)]Br forms and undergoes an intra-molecular C-C coupling reaction between the nitrile carbon and the methylene carbon of the beta-diimine ligand.