Formation of Azabutadienyl Fragments by Addition of the Isopropenyl Substituent of a Phosphine to Benzonitriles, Promoted by an Osmium Center

Abstract

Complex (1) reacts with p-tolunitrile, benzonitrile, and p-chlorobenzonitrile to give the corresponding iminophosphine derivatives (R = CH3 (2), H (3), Cl (4)), as a result of the insertion of the carbon−nitrogen triple bond of the nitriles into one of the C(sp2)−H bonds of the phosphine of 1. Treatment of 2−4 with NaBH4 and methanol produces the rupture of the P−C(CH3) bond of the iminophosphine ligands and the formation of the respective osmapyrrole derivatives (R = CH3 (5), H (6), Cl (7)). The addition of HBF4·Et2O to the diethyl ether solutions of 5−7 leads to the hydride-azabutadienyl-osmium(IV) complexes (R = CH3 (8), H (9), Cl (10)), as a consequence of the protonation of the metallic center of 5−7. Complexes 3 and 10 have been characterized by X-ray diffraction analysis.