Metal-catalyzed hydrocarbon oxygenations in solutions: The dramatic role of additives: a review

This review describes examples of remarkable acceleration of metal-catalyzed oxidation reactions by certain additives. In some cases, reactions proceed 2 or 10 times more rapidly in comparison with the process in the additive's absence, in other cases, reactions become possible only in the presence of the additive. Varying ligands at the metal center or additives, one can not only dramatically improve yields of oxygenates but also control the selectivity of the reaction. Understanding mechanisms of the additive's action is very important for search of new efficient catalysts and catalytic systems. Additives considered in the review can play roles of the ligands at metal ion or proton or electron transfer reagents and they mimic certain enzymes (the active center or its environment). Often the mechanism of the effect of additives on the reaction rate and the product yield is unknown, and the main aim of the review is to attract investigator's attention in creating new efficient catalytic systems, which contain not only a metal ion but also a necessary "additive". (C) 2002 Elsevier Science B.V. All rights reserved.