On the Mechanism of Dihydrogen Activation by Frustrated Lewis Pairs. Insights from the Analysis of Domain Averaged Fermi Holes and Generalized Population Analysis

Abstract

The electron reorganization responsible for the facilitation of heterolytic splitting of H-H bond by frustrated Lewis pair (FLP) catalysts has been studied using the analysis of domain averaged Fermi holes and generalized population analysis. The analysis of electron structures of the species along the reaction path has revealed that the anticipated synchronicity of previously considered electron shifts of electron pair of the σHH bond to a vacant orbital on B and from the lone pair on the basic N site to an antibonding σHH* orbital is associated with the build up of extensive delocalized bonding that can conveniently be characterized in terms of multicenter bond indices. In addition, the detailed scrutiny of the IRC-dependence of the 2-center bond indices of the disappearing H-H bond resulted in the proposal of a simple heuristic measure of the efficiency of the FLP catalysts. Attention was also paid to the evaluation of the presumed facilitating effect on the dissociation of the H-H bond of the electric field in the cavity of FLP catalyst. It has been shown that the strength of this field does not reach the critical values required for the efficient facilitation of the splitting of the H-H bond.