Approach for Introducing a Single Metal Complex into a Polymer Chain: Metallo-Chain Transfer Agents in CO₂ or COS/Epoxide Copolymerization Processes

Abstract

We have designed and synthesized poly­(monothiocarbonate)­s containing a single well-defined metal complex in the polymers’ backbone via the immortal copolymerization of carbonyl sulfide and propylene oxide in the presence of chain transfer agents (CTAs). Our initial studies in this area have involved the utilization of metal carbonyl diols, which serve as CTAs. Included in this investigation are the metal complexes ()­Cr­(CO)3 and ()­Re­(CO)3Br. Because of the electron-withdrawing abilities of the metal carbonyl fragments, the CTA afforded catalyst-alkoxide bonds are not sufficiently nucleophilic to react with CO2; hence, the more reactive carbonyl sulfide analog was employed. As anticipated, the molecular weights of the resulting copolymers decreased with increasing quantities of added metal complexes. The incorporation of the metal complexes directly into the polymers’ backbone was noted by νco infrared and 1H NMR spectroscopies. Estimates of metal loading were obtained using calibration curves of the pure metal complexes based on νco infrared or electronic spectra. Thermal decomposition of the copolymers occurred above 180 °C.

Placing Single-Metal Complexes into the Backbone of CO2-Based Polycarbonate Chains, Construction of Nanostructures for Prospective Micellar Catalysis

“…Unlike the unsuccessful immortal copolymerization of propylene oxide and CO 2 using complex 1 as CTA, the analogous process in the presence of complex 2 readily affords the triblock copolymer as indicated in eq Derivatives of (bipy)­Re­(CO) 3 Br were chosen for our preliminary studies because of their stability and importance to the CO 2 reduction process. , The X-ray structure of the chloride analog of complex 2 is illustrated in Figure .…”

Amphiphilic Polycarbonate Micellar Rhenium Catalysts for Efficient Photocatalytic CO2 Reduction in Aqueous Media

“…Recently, Darensbourg et al. designed a series of CO 2 ‐based amphiphilic block polycarbonates through a living polymerization process and subsequent thiol‐ene click reaction [45–47] . Based on this inspiration, the hydrophilic block can increase solubility of the catalyst in aqueous media so as to enhance the mass transfer among the catalyst and the solutes (sacrificial electron donor and CO 2 ) in water from the point of view of photocatalysis.…”

Progress in the catalytic reactions of CO2 and epoxides to selectively provide cyclic or polymeric carbonates

“…More recently, Darensbourg and coworkers have used metal carbonyl containing diols or dicarboxylic acids as metallo-chain transfer agents during the immortal copolymerization of epoxides and CO 2 to form metallopolymers. 72 Thus, upon employing dicarboxylic acid CTAs which contain discrete metal binding sites, these researchers have synthesized polycarbonate copolymers with a single-metal complex present in each polymer chain. In these ways, the (bipy)Re(CO) 3 Br and (arene)Cr(CO) 3 have been incorporated into the polycarbonate backbone covalently.…”