Applications of Density Functional Theory in the Study of Organometallic Reactivity Problems

Abstract

In this paper we have reported the results of theoretical investigations at the DFT level on the mechanism of some representative organometallic reactions. In all cases the non-local hybrid B3LYP functional has been used. The reactions examined here are: (a) the cyclopropanation reactions promoted by transition metal complexes and (b) the nickel-catalyzed carbonylation reactions. In the former case we have considered in details the Simmons-Smith reaction and the cyclopropanation promoted by palladium complexes. It has been found that the active cyclopropanating reagent is always a carbenoid species [L]-M-CH₂-X (I., X = ligands) and that the cyclopropanation promoted by palladium complexes proceeds either via a concerted mechanism or a multi-step mechanism involving palladacyclobutane intermediates. For the carbonylation reactions we have examined in details the mechanism of the insertion of a CO molecule into a nickel-carbon bond. This step corresponds to a complicated process involving either four-coordinated or five-coordinated nickel complexes.