Investigations on the catalytic carboxylation of olefins with CO<sub>2</sub> towards α,β-unsaturated carboxylic acid salts: characterization of intermediates and ligands as well as substrate effects
salts and a detailed investigation on the critical steps in the catalysis are reported. The influence of two chelating phosphine ligands and several olefins on the elemental steps of the catalysis is shown. The work focusses on the formation of intermediate olefin complexes, lactoneformation and base induced elimination of the lactone. The direct carboxylation of olefins is possible using nickel catalysts