The H 2 -Cleavage by Frustrated Lewis Pairs Characterized by the Energy Decomposition Analysis of Transition States: An Alternative to the Electron-Transfer and the Electric-Field Models

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2018-09, Vol.122 (36), p.7202-7211
• Main Authors: Heshmat, Mojgan, Privalov, Timofei
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215; 1520-5215
• DOI: 10.1021/acs.jpca.8b06830

Knowing that the Papai's electron transfer (ET) and the Grimme's electric field (EF) models draw attention to somewhat different physical aspects, we are going to systematically (re-)examine interactions in the transition states (TSs) of the heterolytic H2-cleavage by the Frustrated Lewis Pairs (FLPs). Our main vehicle is the quantitative energy decomposition analysis (EDA) - a powerful method for elucidation of interactions - plus the analysis of molecular orbitals (MOs). Herein, the Lewis acid (LA) is B(C6F5)3 and the Lewis bases (LBs) are tBu3P, (o-C6H4Me)3P, 2,6-lutidine, 2,4,6-lutidine, MeN=C(Ph)Me imine, MeN(H)-C(H)PhMe amine, THF, 1,4-dioxane and acetone. For a series of the phosphorous-, nitrogen- and oxygen-bearing LBs plus B(C6F5)3, we will show that (i) neither the electrostatic- nor the orbital-interactions dominate but instead both are essential alongside the Pauli repulsion; (ii) the frontier molecular orbitals (FMOs) of a TS can arise not only from the "push-pull" molecular orbital scheme by Papai et al., which directly involves the occupied σ and the empty σ* MOs of H2, but also from a more intricate but energetically more fitting orbital-interactions which have escaped notice thus far.