Alternating copolymerization of carbon dioxide and cyclohexene oxide catalyzed by salen CoIII(acetate) complexes

Abstract

A series of CoIII carboxylate based upon N,N,O,O-tetradentate Schiff base ligand framework have been prepared. X-ray diffraction analysis confirms that these Schiff base CoIII carboxylate are all monomeric species with a six-coordinated central Co in their solid structures. The activities and polycarbonate selectivity of these complexes toward the copolymerization of epoxide (cyclohexene oxide and propylene oxide) and carbon dioxide have been investigated in the presence of bis(triphenylphosphine)iminium chloride. Copolymerization experiments indicate that [bis(α-methyl-3,5-di-tertbutyl-salicylaldehyde) ethylenediiminato] CoIIIOOCH3 exhibits the highest activity and polycarbonate selectivity among these CoIII carboxylate. The resultant copolymer contained almost 100 % carbonate linkages with the molecular weight up to 71.8 kg mol−1 as well as narrow polymer dispersity index (polymer dispersity index = 1.5). The substituents and the mode of the bridging part between the two nitrogen atoms both exert significant influences upon the progress of the copolymerizations, influencing both the polycarbonate selectivity and the rate of copolymerization.

Green polycarbonates prepared by the copolymerization of CO2 with epoxides

“…MALDI‐ToF MS also provides information about the molecular weight of the polymer, though the higher molecular weight fraction is generally not observed with this technique . In the MALDI‐ToF mass spectra of CO 2 –epoxide copolymers, consecutive mass losses corresponding to the epoxide and CO 2 can be observed . The observed m/z values correspond to polymers masses expressed as n M repeating unit + M terminal groups .…”

“…27,43 In the MALDI-ToF mass spectra of CO 2 -epoxide copolymers, consecutive mass losses corresponding to the epoxide and CO 2 can be observed. 68 The observed m/z values correspond to polymers masses expressed as nM repeating unit 1 M terminal groups . 27,64 The terminal groups are typically -OH groups or the nucleophile that started the reaction by ring opening of the epoxide (Figure 9).…”

Copolymerization of carbon dioxide and propylene oxide by several metallosalen‐based bifunctional catalysts

“…Furthermore, much research demonstrated that salen–metal complexes show higher catalytic activity and selectivity . The special features of these complexes are that the molecular weight of the polymers can be controlled and polymers can be separated on the basis of the distribution of molecular weight …”

“…[8] The special features of these complexes are that the molecular weight of the polymers can be controlled and polymers can be separated on the basis of the distribution of molecular weight. [9] In the present paper, we have designed and synthesized a new salen ligand bearing quaternary ammonium salts (Scheme 2). Based on the previous results, the research focused on 2,4-dinitrophenoxy as both the axial anion X and the counter anion Y in this ligand.…”

Copolymerization of Carbon Dioxide and Propylene Oxide by Binary Cobalt Salen Complexes with Various Anion Groups

“…Through slight changes of the catalyst structures, the copolymerization can be tuned to favor the formation of the desired product. Among of them, metal–salen complexes has gained considerable attention over the past decade, which is due to their advantages of simple preparation, high catalytic activity, and easy‐to‐change structure. More recently, functional metal–salen‐complex‐based catalysts have received much attention, especially using single‐component bifunctional metal–salen complexes instead of binary catalysts.…”