The insertion of acetylene into the palladium carbon bond of square planar Pd(II) complexes: a theoretical investigation

Abstract

Ab-initio SCF, CAS-SCF and CI calculations have been carried out for the acetylene insertion into the PdC bond of the [PdCl(NH 3)(CH 3)(C 2H 2)] model system. The acetylene is found to bind quite weakly to the palladium atom and inserts with an activation barrier of 17 kcal mol −1. The geometry of the transition state corresponds to a monohapto coordination of the acetylene. No intermediate seems to be involved on the reaction path, at least for the C 2H 2 system. The effects of substitution of one hydrogen atom by more electron attracting substituents and of a CH group by a metal organic entity are briefly analysed. The stereochemical course of the reaction is also investigated in connection with the geometry of the various isomers known for the isolobal C 3H 5 + organic system.