Iron-Catalyzed Polymerization of Isoprene and Other 1,3-Dienes

摘要

Iron is the most abundant transition metal in the Earth's crust. As such, it is potentially useful for catalysts that can be employed in high-volume processes, like the Haber-Bosch process that functions with iron oxide as the precatalyst. Maintaining the economic and environmental benefit of iron catalysis, well-defined molecular iron catalysts provide the opportunity to also control selectivity, such as stereoselectivity, during catalysis, if the ligands employed are appropriately selected. Here we report on the iron-catalyzed polymerization of 1,3-dienes to afford elastomers with catalyst content as low as 0.02 mol %. Iminopyridine ligands, as part of the catalyst and made in one step from commercially available chemicals in the case of catalyst 1, can control and invert the stereoselectivity of the polymerization.