Coordination catalysts for the selective hydrogenation of polymeric unsaturation

The selective hydrogenation of poly-1,4-butadiene in the presence of poly-1,4-isoprene is described. Both of these polydienes are hydrogenated more easily than polystyrene. The catalysts which effect these selective hydrogenations are made by the reaction of organoaluminum or lithium compounds with transition metal salts of 2-ethylhexanoic acid.