A One-Component Iron Catalyst for Cyclic Propylene Carbonate Synthesis

The development of a new tetraamine-iron complex as a catalyst for the cyclization of propylene oxide with carbon dioxide to form propylene carbonate is reported. The structure of the complex was confirmed by X-ray crystallography. The molecule exhibited an exceptionally long iron-chlorine bond and a high catalytic activity even without the addition of an activator. However, kinetic studies showed a second-order dependence on catalyst concentration. By using iron, we provide an ecologically as well as economically favourable alternative to the preferentially used toxic metals cobalt and chromium. On the basis of the kinetics and other experimental data, the catalytic cycle deduced as well as an understanding of the high activities.