Mechanistic Pathways in the Catalysis of Olefin Hydrocarboxylation by Rhodium, Iridium, and Cobalt Complexes

Carboxylic acids can be synthesized by reacting olefins with carbon monoxide and water in the presence of a variety of transition transition metal catalysts: (1) Metals which have been employed as catalysts for this reaction include nickel, as first reported [1] by Reppe for the synthesis of acrylic and propionic acids from acetylene and ethylene, cobalt, iron, rhodium, ruthenium, palladium, and platinum [2]. The earlier studies of this reaction employed nickel, cobalt, and iron catalysts and required rather severe operating conditions, viz., 200-300 atm and 200-300°C. More recently the use of rhodium [3], iridium [4], platinum [5], palladium [6], and pyridine-promoted cobalt [7] catalysts has been reported. These latter systems all function at relatively mild reaction conditions (see Table 1).