Bifunctional cobalt Salen complex: a highly selective catalyst for the coupling of CO₂ and epoxides under mild conditions

Abstract

A bifunctional cobalt Salen complex containing a Lewis acid metal center and two covalent bonded Lewis bases on the ligand was designed and used for the coupling of CO 2 and epoxides under mild conditions. The complex exhibited excellent activity (turnover frequency = 673/h) and selectivity (no less than 97%) for polymer formation in the copolymerization of propylene oxide (PO) and CO 2 at an appropriate combination of all variables. High molecular weight of 110 200 and yield 99% were achieved at a higher [PO]/[complex] ratio of 6000 : 1. The complex also worked satisfactorily for the terpolymerization of CO 2 , PO and cyclohexene oxide (CHO), without formation of cyclic carbonate or ether linkages to give the polycarbonate. High cyclohexene carbonate unit content in the CO 2 /PO/CHO terpolymers resulted in enhanced thermal stability.

Recent progress in catalytic conversions of carbon dioxide

“…18). 25 The copolymerization of CO 2 with propylene oxide selectively produced the alternating copolymer. In addition, the terpolymerization of CO 2 , propylene oxide and cyclohexene oxide with a high cyclohexene carbonate content was also realized without the formation of cyclic carbonates or ether linkages.…”

Photoluminescence of Zinc Complexes: Easily Tunable Optical Properties by Variation of the Bridge Between the Imido Groups of Schiff Base Ligands

“…[4] Recently, their range of applicability was extended to photopolymerization, [5] and they have the unique ability to photoinitiate the polymerization without coloration of the photoresist film. [6] Various metal cations have been complexed to salicylaldehyde Schiff base ligands, and notable metal chelate complexes have been prepared with iron, [7] copper, [8] zinc, [9] cobalt, [10] nickel, [11] titanium, [12] silicon, [13] scandium, [14] and rhodium [15] as the metal cation. [6] Various metal cations have been complexed to salicylaldehyde Schiff base ligands, and notable metal chelate complexes have been prepared with iron, [7] copper, [8] zinc, [9] cobalt, [10] nickel, [11] titanium, [12] silicon, [13] scandium, [14] and rhodium [15] as the metal cation.…”

Functional Polycarbonates from Carbon Dioxide and Tailored Epoxide Monomers: Degradable Materials and Their Application Potential

“…As expected for a terpolymer, the properties of the two theoretical copolymers were combined ( Figure ) . Several other groups also observed the adjustability of the glass‐transition temperature and described enhanced thermal stability due to an increase of the cyclohexene carbonate content . Furthermore, Darensbourg et al described mechanistic aspects of the terpolymerization of alicyclic and aliphatic epoxides with CO 2 in toluene solution and in neat epoxides in the presence of a (salen)CrCl/onium salt catalyst system …”