AB-INITIO MOLECULAR-ORBITAL AND EXPERIMENTAL STUDIES OF HYDRIDE ADDITION TO PHOSPHINE-SUBSTITUTED MANGANESE CARBONYL-COMPLEXES

Ab initio molecular orbital calculations on [Mn(CO)(6)](+), [Mn(CO)(5) (PH3)](+), and the formyl and hydride complexes derived from these sho w that the increased stability of cis-Mn(CO)(4)(PR(3))(CHO) and simila r formyl complexes is largely kinetic in origin. The transition state for the unsubstituted formyl complex, which forms the corresponding hy dride by a simple dissociative mechanism, differs from the transition states for the substituted formyl complexes, which form the correspond ing hydrides by concerted mechanisms. Experimental studies of hydride addition to diphenylphosphinoalkane-substituted hexacarbonylmanganese cations are in accord with the theoretical conclusions.