Nickel and Palladium Complexes with Reactive σ-Metal-Oxygen Covalent Bonds

Abstract

This article reviews the chemistry of nickel and palladium complexes with terminally bound hydroxide and alkoxide ligands. The research carried out in our group is discussed in the context of the general literature. It is shown that suitable methods of synthesis, combined with the choice of adequate ligands allow the isolation of a range of stable complexes. This has enabled a detailed investigation of the chemical reactivity of the M−O bonds, once believed to be intrinsically weak. The elucidation of trends in thermodynamic stability and kinetic lability is the key for a better understanding of the reactivity of this class of compounds, that combines basic and nucleophilic properties with typical organometallic patterns, like β-hydrogen elimination. Based on reversible acid-base exchange and CO2 insertion reactions, we discuss how the polarity of the M-OR bonds influence their relative stability, their hydrolytic sensitivity and their tendency to react with electrophiles.