Mechanistic insights into B–H bond activation with the high-valent oxo-molybdenum complex MoO2Cl2?

New Journal of Chemistry Pub Date: 2014-09-01 DOI: 10.1039/C4NJ01188K

Abstract

The B–H bond activation and the catalytic hydroboration of carbonyl compounds by the high-valent oxo-molybdenum complex MoO2Cl2 were theoretically investigated to determine the underlying mechanism. Our calculation results indicate an unique path – the ionic mechanistic pathway involving the heterolytic cleavage of the B–H bond competes with the [2+2] addition pathway, which involves the addition of the B–H bond across one of the Mo[double bond, length as m-dash]O bonds. The rate-determining free energy barriers for the ionic mechanistic pathway are calculated to be 26.9 kcal mol?1, 25.0 kcal mol?1 and 23.7 kcal mol?1 for diphenylketone, benzaldehyde and acetophenone, respectively. These values are energetically slightly favorable than the [2+2] addition mechanism by ～1–3 kcal mol?1. Furthermore, it is worth noting that the carbonyl compounds bearing the electron donation group will induce a better activity toward the ionic mechanistic pathway.

Graphical abstract: Mechanistic insights into B–H bond activation with the high-valent oxo-molybdenum complex MoO2Cl2
Recommended Literature