Kinetic Isotope Effect Associated with the Dissociative Addition of Dihydrogen to trans-Ir(CO)Cl(Ph3P)2

Article abstract of DOI:10.1021/ja00312a042

The temperature dependence of the kinetic isotope effect for the dissociative addition of dihydrogen and dideuterium to trans-Ir(CO)(Cl)(Ph3P)2 in toluene has been determined between 0 and 30 deg C.Model calculations based on these data suggest that the transition state for dissociation is best formulated as triangular with reactant-like character and involves substantial hydrogen tunneling.The weak KIE (k_H/k_D ca. 1-2) generally observed for the dissociative addition of dihydrogen to transition-metal complexes is seen to be a consequence of the product of an unusually large MMI factor, a moderately inverse EXC term and a substantially inverse ZPE factor.Only the tunnel correction prevents the overall KIE from being inverse.