Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes.

Yo Hiranoi,Koji Nakano

doi:10.3762/bjoc.14.255

Abstract

The alternating copolymerization of epoxides with cyclic anhydrides (CAs) is a highly diverse synthetic method for polyesters as the polymers’ architectures and properties can be easily controlled depending on the combination of two monomers. Thus, a variety of catalyst designs has been reported to prepare the desired copolymers efficiently. We herein report dinuclear cobalt–salen complexes with a benzene ring as a linker and their activities in copolymerization reactions. The dinuclear cobalt complexes showed a higher catalytic activity for the copolymerization of propylene oxide with phthalic anhydride than the corresponding mononuclear cobalt–salen complex and achieved one of the highest turnover frequencies ever reported. A variety of epoxides and CAs were also found to be copolymerized successfully by the dinuclear cobalt complex with a high catalytic activity.

Highlights

Aliphatic polyesters have received significant attention owing to their good biocompatibility and biodegradability [1,2,3,4]
The substituents at the 5-positions and the axial ligand of mononuclear cobalt–salen complexes were proven to have a great impact on the catalytic activity [15]
We reported the alternating copolymerization of epoxides with cyclic anhydrides using dinuclear cobalt–salen complexes with a benzene linker

Summary

Introduction

Aliphatic polyesters have received significant attention owing to their good biocompatibility and biodegradability [1,2,3,4]. In 2013, Lu and co-workers reported that the dinuclear chromium–salan complex showed a much higher catalytic activity than the corresponding mononuclear chromium–salan complex in the copolymerization of epoxides with maleic anhydride (MA) [31]. During the course of our study, the dinuclear cobalt–salen complex (R,R,S,S)-1 was found to exhibit a high catalytic activity for the alternating copolymerization of propylene oxide (PO) with phthalic anhydride (PA, Figure 1).

Results

Conclusion