FROM STOICHIOMETRY TO CATALYSIS - ELECTROREDUCTIVE COUPLING OF ALKYNES AND CARBON-DIOXIDE WITH NICKEL BIPYRIDINE COMPLEXES - MAGNESIUM-IONS AS THE KEY FOR CATALYSIS

The incorporation of carbon dioxide into nonactivated alkynes catalyzed by electrogenerated nickel-bipyridine complexes affords alpha,beta-unsaturated acids in moderate to good yields. The electrocarboxylation reaction was undertaken on a preparative scale in the presence of a sacrificial magnesium anode: the formation of acids from alkynes is stoichiometric with respect to the nickel complex if performed in a two-compartment cell but can be made catalytic in a single-compartment cell. An intermediate nickelacycle was isolated from the reaction with 4-octyne. The cleavage of this metallacycle by magnesium ions is the key step to explain catalysis.