Formation of Complexes from Azobenzenes and Cyclopentadienyl Cobalt Derivatives

New complexes (III) have been found to be formed in the reaction between aromatic azo compounds and cyclopentadienyl cobalt derivatives. The same complexes have also been obtained from the reaction of o-quinonediimine or o-phenylenediamine derivatives with cyclopentadienyl cobalt dicarbonyl. These complexes reacted with carbon monoxide to yield benzimidazolone derivatives, and with hydrogen to give o-phenylenediamine derivatives. The structure of the complexes has been formulated on the basis of the infrared spectra, the proton magnetic resonance, and chemical evidence.