Placing Single-Metal Complexes into the Backbone of CO<sub>2</sub>-Based Polycarbonate Chains, Construction of Nanostructures for Prospective Micellar Catalysis
Gulzar A. Bhat, Ahmed Z. Rashad, Tucker M. Folsom, Donald J. Darensbourg
Abstract
The copolymerization of CO2 and epoxides in the presence of chain-transfer agents (CTAs) has provided a well-controlled route to polycarbonate polyols. Upon employing dicarboxylic acid CTAs which contain discrete metal-binding sites, it is possible to synthesize polycarbonates with a single-metal complex present in the main chain, either during the copolymerization process or in a postpolymerization procedure. In these ways, the (bipy)Re(CO)3Br complex has been incorporated into the polycarbonate backbone. Furthermore, in a one-pot, two-step synthesis, a second epoxide containing a vinyl substituent can be introduced to afford a triblock ABA polycarbonate, where the metal is contained in the B block. Subsequent to the thiol–ene click chemistry of HS∧COOH and deprotonation, the resulting anionic polymer is shown to self-assemble in deionized water to provide rather uniform, spherical micelles. Since this procedure is modular, it is applicable to a wide variety of CTAs containing metal complexes or metal-binding sites, thereby providing a pathway to synthesize a wide range of micellar catalysts for pursuing organometallic transformations in water.