A study of bond-cleavage and bond-formation processes in some simple metathesis reactions

Abstract

A few simple atom-transfer reactions (i.e., A + X - A \rightarrow A - X + A) are studied by quantum mechanical ab initio methods. Emphasis is given to the detailed analysis of density matrices rather than to the energetics. Results reveal that during these reactions a small free valence always develops on the migrating atom at the transition state. The barriers in these reactions arise from the greater extent of bond cleavage in the reactant than that of bond formation in the transition state. Analysis of bond orders estimated from bond lengths using Pauling’s relation also leads to the fact that the bond-cleavage process is more advanced than is the bond-formation process in these reactions.