Deactivation in Homogeneous Transition Metal Catalysis: Causes, Avoidance, and Cure

Active catalysts typically have labile sites that are in principle much more sensitive to all the species present in the reaction medium as well as to the ambient conditions than is a stable complex in solution. The effects of changing solvents, additives, and conditions may therefore have big effects. Avoiding impurities in the solvent or substrate can also be a help, big or small depending on the case. The relevance of the topic is not limited to catalyst chemists. Many researchers, not themselves specialists in the field, apply a homogeneous catalyst taken from the literature in the hope of obtaining a needed organic product or bringing about some desired transformation. These efforts sometimes go astray from neglect of some unstated assumption in the original work or from a change either in the substrate structure or in the conditions used in the prior reports.