Olefin carbonylation catalysis with cationic palladium complexes: Selectivity and possible intermediates

Palladium complexes L2PdX2 containing various group Va ligands and weakly coordinating anions are active catalysts for the carbonylation of olefin substrates. These catalytic systems, though gaining significance in industry for the synthesis of polyketones, are normally characterised by a low chemoselectivity. This derives from the numerous possibilities for initiation and termination reactions which lead to different catalytic cycles and from facile multiple alternating insertion reactions of olefins and carbon monoxide. Based on experiments carried out under conditions of low selectivity and on previously published data, the factors involved in the control of the regio-, chemo- and stereoselectivity for those reactions are discussed, taking current ideas and model studies involving the above palladium complexes into consideration.