Alcohol electrooxidation catalysts from degraded polyanionic chelating ligand complexes. The uncertainty for catalyst identification that accompanies a decomposing catalytic system

Abstract

Electrooxidation of trans-Os(eta/sup 4/-CHBA-Et)(py)/sub 2/, H/sub 4/CHBA-Et = 1,2-bis(3,5-dichloro-2-hydroxybenzamido)ethane, in the presence of alcohols led to the discovery of several catalytic systems for the electrooxidation of alcohols. The catalytic systems are formed via the oxidative and hydrolytic degradation of the ethylene unit of the polyanionic chelating (PAC) ligand (eta/sup 4/-CHBA-Et)/sup 4 -/ in a sequence that involves 15 observable species. The principal species in the catalytically active solutions have been identified. The uncertainty for catalyst identification that is inherent with decomposing catalyst systems is discussed. At high alcohol concentrations, primary alcohols are oxidized to aldehydes. Pure aldehydes are not oxidized. However, it has not been possible to study the catalytic oxidations at high concentrations of both primary alcohols and aldehydes. Cyclohexanol is oxidized to cyclohexanone. All the species in the degradation sequence are closely related. It is suggested that the principal species in the catalytic solutions might be able to carry out rapid inner-sphere oxidations of alcohols because of a higher affinity for alcohols than the noncatalysts in the degradation sequence. 12 references, 4 figures, 3 tables.