Cyclic Carbonate Formation from Carbon Dioxide and Oxiranes in the Presence of Organotin Halide-Complexed Catalysts

Abstract

Catalytic capability of complexes between Bu₃SnI or Bu₂SnI₂ and some ligands such as Ph₃P, Ph₃P=O, Bu₄PI, and Ph₄SbI was examined for the cycloaddition of carbon dioxide to oxiranes. Some complexes showed quite high activity, though the individual component of the complexes did not individually. The combination between tin compounds and ligands was essential. For example, Bu₃SnI-Ph₃P showed quite low activity in contrast to the active Bu₂SnI-Ph₃P complex. Catalytic activity depended strongly on the stability and structure of complexes. In addition, the activities of these complexes were compared with those in the polymerization of trimethylene carbonate. It was revealed that the Lewis acidity of organotin halides was weakened by the complexations, because the polymerization using the complexes, Bu₃SnI-Bu₄PI [E] and Bu₃SnI-Ph₄SbI [G] was remarkably suppressed.
Consequently, both complex [E] and [G] were excellent catalysts, cle arly producing several kinds of carbonates under mild conditions as shown in Table 4.