The Cobalt-Catalyzed Ketene Formation from Diazoalkanes

Various carbonyl cobalt complexes were found to be suitable catalyst precursors for the selective transformation of aliphatic primer diazoalkanes into the corresponding ketenes. Stable ketene such as (trimethylsilyl) ketene was isolated from the reaction mixtures in high yield. Highly reactive ketene such as ethoxycarbonylketene was isolated as its dimer or in the presence of proper reactants as in situ addition products in high yields. In the ethoxycarbonylketene formation intermediate cobalt complexes were identified and characterized. Their role in the catalytic carbonylation reaction was verified by spectroscopic and kinetic investigations. Results of theoretical calculations revealed details of the suggested mechanism.