The coordination chemistry of carbon dioxide and its relevance for catalysis: A critical survey

The ability of carbon dioxide to act as a ligand in transition metal complexes is now well documented and several coordination modes of CO2 have been described. Spectroscopic methodologies allowing the characterization of CO2 complexes even if crystallographic data are not available have now been developed. The binding of CO2 to a metal centre generally leads to ''activation'' of the CO2 molecule, and various reactions of coordinated CO2 are known. However, activation by coordination is not a necessary prerequisite for catalytic conversion of carbon dioxide to useful chemicals. Recent theoretical and experimental work suggests that only weak interactions between CO2 and the active metal centre are sufficient to bring about catalytic reactions involving the formal insertion of CO2 in an M-X bond as a key step.