ISOCYANIDE LIGANDS IN TP'(CO)2IMO(CNR) COMPLEXES AS PRECURSORS TO AMINOCARBYNE, ETA-2-IMINOACYL, AND ETA-2-VINYL LIGANDS

A mixture of molybdenum aminocarbyne, eta-2-iminoacyl, and eta-2-acyl complexes, Tp'(CO)2Mo = CN(Me)(Bu(t)), Tp'(CO)2Mo(eta-2-C(NBu(t))Me), and Tp'(CO)(Bu(t)NC)Mo(eta-2-C(O)Me), has been prepared via the addition of MeI to the anionic tert-butyl isocyanide complex [Na][Tp'(CO)2Mo(CNBu(t))]. Addition of MeI to the analogous anionic methyl or phenyl isocyanide complex yields only aminocarbyne complexes. The eta-2-iminoacyl complex can be deprotonated at the C-beta methyl site with KH to give an anionic eta-2-enamide intermediate, and quenching with MeI yields the ethyl product, Tp'(CO)2Mo(eta-2-C(NBu(t))Et). The eta-2-iminoacyl complex undergoes cleavage in air to give N-tert-butylacetamide. Protonation of Tp'-(CO)2Mo = CN(Me)(Bu(t)) in the presence of phenylacetylene ultimately yields a cationic eta-2-vinyliminium complex, [Tp'(CO)2Mo(eta-2-C(Ph) = C(H)C(H) = N(Me)(Bu(t)))][BF4]. This material is fluxional in the H-1 NMR spectrum due to rapid inversion at the vinyl beta-carbon. The X-ray structure of this eta-2-vinyl cation is reported. A neutral eta-2-vinylamine complex, Tp'(CO)2Mo(eta-2-C(Ph) = C(H)CH2N(Me)(Bu(t))), has been synthesized by addition of LiEt3BH to the cationic eta-2-vinyliminium complex.