Abstract
Since the prominent application of the Wilkinson complex to the hydrogenation of olefins, many organic reactions catalyzed by rhodium complexes and iridium analogs have been reported. In this review, the preparative methods, properties of rhodium compounds and their applications to organic synthesis as well as those of iridium compounds are described. Rhodium and iridium compounds are generally prepared starting from their water-soluble halogeno compounds such as RhCl3·3H2O or IrCl3H2O. The oxidation state of the compounds obtained is strongly dependent on the nature of the ligands. Low-valent (from -3 to zero) complexes are stabilized by carbon monoxide which behaves as a strong π-acceptor. Uni-valent complexes are coordinated by olefins, dienes, carbon monoxide, phosphines, arsines or amines. Most of low-valent complexes are air-sensitive and should be handled under inert atmosphere. They easily undergo the oxidative addition reaction and catalyze organic reactions, such as hydrogenation, hydrosilylation, hydroformylation, oligomerization, isomerization, carbonylation, decarbonylation, etc.
