Carbonyl complexes of manganese, rhenium and molybdenum with ethynyliminopyridine ligands

MBr(CO)₅] reacts with m-ethynylphenylamine and pyridine-2-carboxaldehyde in refluxing tetrahydrofuran to give, fac-MBr(CO)₃(py-2-CHN-C₆H₄-m-(CCH))] (M = Mn, 1a; Re, 2a). The same method affords the tetracarbonyl Mo(CO)₄{py-2-CHN-C₆H₄-m-(CCH)}] (3a) starting from Mo(CO)₄(piperidine)₂]; and the methallyl complex MoCl(η³-C₃H₄Me-2)(CO)₂{py-2-CHN-C₆H₄-m-(CCH)}] (4a) from MoCl(η³-C₃H₄Me-2)(CO)₂(NCMe)₂]. The use of p-ethynylphenylamine gives the corresponding derivatives (1b, 2b, 3b, and 4b) with the ethynyl substituent in the para-position at the phenyl ring of the iminopyridine. All complexes have been isolated as crystalline solids and characterized by analytical and spectroscopic methods. X-ray determinations, carried out on crystals of 1a, 1b, 2a, 2b, 3b, 4a, and 4b, reveals the same structural type for all compounds with small variations due mainly to the different size of the metal atoms. The reaction of complexes 1a or 2a with dicobalt octacarbonyl affords the tetrahedrane complexes MBr(CO)₃{py-2-CHN-C₆H₄-m-{(μ-CCH)Co₂(CO)₆}}] (M = Mn, 5; Re, 6), the structures of which have been confirmed by an X-ray determination on a crystal of compound 5.