Theoretical analysis of the hydrogen-transfer reaction to C=N, C=C, and C C bonds catalyzed by Shvo's ruthenium complex

摘要

The Shvo catalyst {[Ph-4(eta(5)-C4CO)](2)H}Ru-2(CO)(4)H belongs to the so-called bifunctional catalysts, containing one hydride (bonded to Ru) and one proton (bonded to a ligand), which are easily transferred. The mechanism of hydrogenation of polar double bonds by Shvo's catalyst has been extensively studied; however, imine hydrogenation is still a controversial topic. The outer-sphere mechanism (without substrate coordination) and the inner-sphere mechanism (with substrate coordination) are the two main proposals. Several experimental observations account for each proposed mechanism, besides a theoretical analysis of their respective suggested mechanism. In the present work inner- and outer-sphere mechanisms for hydrogenation of C=N, C=C, and C=-C bonds are analyzed and compared by means of theoretical calculations, complementing our previous work in C=O hydrogenation. The obtained energy profiles support an outer-sphere mechanism in all the cases.