Bimetallic Nickel Complexes as Effective and Versatile Catalysts for Copolymerization of Epoxides with Carbon Dioxide or Phthalic Anhydride: Catalysis and Kinetics

Abstract

This study reported three novel structurally wellcharacterized dihalide dinuclear nickel complexes containing benzotriazole-based 1,3-diamine-linked bisphenolate ligands, which were highperformance catalysts for ring-opening copolymerization (ROCOP) of cyclohexene oxide (CHO) and carbon dioxide (CO 2 ). The dinickel diiodo 3 was shown to catalyze CO 2 copolymerization of CHO with high activity (turnover frequency up to 2250 h −1 ), excellent selectivity (>99% polycarbonates, >99% carbonate repeated units), and good molecular weight controllability. Apart from CO 2 /CHO copolymerization, the most active complex 3 was found to effectively catalyze ROCOP of CHO with phthalic anhydride (PA). Not only has the controllable manner of 3 for PA/CHO copolymerization been proven but also a broad substrate scope for PA copolymerization of epoxides by the same complex has been achieved. Diverse terminal or internal epoxides were demonstrated to copolymerize PA by 3, producing the corresponding semiaromatic polyesters with good activity and excellent product selectivity. Kinetic studies for CHO copolymerization of CO 2 or PA mediated by 3 were systematically investigated. For kinetics of PA/CHO copolymerization, it allowed us to propose the rate equation of −d[CHO]/dt = k p [3] 1 [PA] 0 [CHO] 1 , and such catalysis displayed a first-order dependence on both dinickel complex and CHO concentrations as well as a zero order for PA. This work offers a bimetallic dihalide nickel complex as an efficient and versatile catalyst for two different types of copolymerization catalysis.

Bimetallic nickel complexes containing imidazole-based phenolate ligands as efficient catalysts for the copolymerization of carbon dioxide with epoxides

“…These results indicated that not only did the acetate moiety initiate the polymer chain growth, but also the chain transfer copolymerization took place because of the presence of protic species during the catalytic process. 33,47 For comparison of catalytic performances for nickel complex-mediated CO 2 /CHO copolymerization, structurally-related dicarboxylate dinickel complexes containing various N-heterocycle-based 1,2-diamine-bisphenolate ligands were chosen, as shown in Scheme S2 †. These selected binickel complexes ( A–C and 1 ) include ligand scaffolds that contain benzotriazole, pyrazolyl, benzothiazole or imidazole groups as the pendant heterocycle donor.…”

“…Recently, the development of the binickel-complex-catalyzed copolymerization of CO 2 with alicyclic epoxides by nitrogen-containing heterocycle-derived phenolate derivatives has been achieved by our group. 28–33 The ligand frameworks in these bimetallic Ni complexes are mainly attributed to N-heterocycle-based bis(iminophenolate) and bis(aminophenolate) derivatives, which can take part in O 2 N 4 -hexadentate chelation for the construction of dinuclear nickel complexes. Among these ligand scaffolds, several different N-involving heterocyclic moieties, such as benzotriazole, pyrazolyl and benzothiazole groups, were successfully bonded to diamine-bisphenolates, as exhibited by types A–C in Chart 1, and the corresponding dinickel complexes could be synthesized to evaluate their catalytic performances for the ROCOP of CHO with CO 2 .…”

High-Activity and High-Selectivity Air-Stable Nickel and Copper Complexes for Copolymerization of Epoxides with Anhydrides

“…Thus, we found that different acid–base conditions resulted in the synthesis of diverse structures. All nickel and copper complexes were characterized through UV–vis spectra (Figure S1), elemental analysis, and single-crystal X-ray crystallography …”

Ring Opening Copolymerization of Epoxides with CO2 and Organic Anhydrides Promoted by Dinuclear [OSSO]‐type Metal Complexes

“…[4][5][6] In addition, the resulting copolymers (bearing esters and carbonate functionalities) possess, in principle, cleavable bonds with the possibility of obtaining hydrolyzable polymeric materials. [7][8][9][10] Indeed, ROCOP is usually catalyzed by metal complexes with various ligand frameworks [11][12][13] able to activate the ring opening of the epoxides and the alternating insertion of the cyclic anhydride or CO 2 following the reaction pathways depicted in Scheme 1.…”