Copolymerization of Phthalic Anhydride with Epoxides Catalyzed by Amine-Bis(Phenolate) Chromium(III) Complexes

Abstract

The effect of ligand structure on the catalytic activity of amine-bis(phenolate) chromium(III) complexes in the ring-opening copolymerization of phthalic anhydride and a series epoxides was studied. Eight complexes differing in the donor-pendant group (R1) and substituents (R2) in phenolate units were examined as catalysts of the model reaction between phthalic anhydride and cyclohexane oxide in toluene. They were used individually or as a part of the binary catalytic systems with nucleophilic co-catalysts. The co-catalyst was selected from the following organic bases: PPh3, DMAP, 1-butylimidazole, or DBU. The binary catalytic systems turned out to be more active than the complexes used individually, and DMAP proved to be the best choice as a co-catalyst. When the molar ratio of [PA]:[epoxide]:[Cr]:[DMAP] = 250:250:1:1 was applied, the most active complex (R1-X = CH2NMe2, R2 = F) allowed to copolymerize phthalic anhydride with differently substituted epoxides (cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, phenyl glycidyl ether, propylene oxide, butylene oxide, and epichlorohydrin) within 240 min at 110 °C. The resulting polyesters were characterized by Mn up to 20.6 kg mol−1 and narrow dispersity, and they did not contain polyether units.

Ring opening polymerization and copolymerization for polyester and polycarbonate formation by a diamino-bis(phenolate) chromium(iii) catalyst

“…They observed that in the absence of a co-catalyst the Cr complex itself gave only 2% conversion of PA to polyester with a high degree of ether linkages. 26 However, upon addition of Lewis bases such as triphenylphosphine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1-butylimidazole or DMAP, PA to polyester conversions up to 42% were obtained using equimolar amounts of catalyst to Lewis base and equimolar amount of PA to CHO in 0.5 mL of toluene at 110 °C and 1 h reaction time. 26 Reaction times of 4 h for the Cr complex with DMAP gave higher PA conversions of 95% with low ether linkages, molar masses up to 12.6 kg mol −1 and dispersities of 1.21.…”

“…26 However, upon addition of Lewis bases such as triphenylphosphine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1-butylimidazole or DMAP, PA to polyester conversions up to 42% were obtained using equimolar amounts of catalyst to Lewis base and equimolar amount of PA to CHO in 0.5 mL of toluene at 110 °C and 1 h reaction time. 26 Reaction times of 4 h for the Cr complex with DMAP gave higher PA conversions of 95% with low ether linkages, molar masses up to 12.6 kg mol −1 and dispersities of 1.21. Comparing these results to our catalyst system (Table 2, entry 2) the use of PPNCl obtains full conversion of PA to polyester within the same time frame with a M n of 8.1 kg mol −1 and Đ of 1.12.…”

“…24 Others have used Cr(III) catalysts for the ROCOP of epoxides such as CHO with PA. [25][26][27] Bester and co-workers used amino-bis( phenolate) Cr(III) complexes with 4-(dimethylamino)pyridine (DMAP) as a co-catalyst. 26 Boggioni used (salen)MCl catalysts, where M = Cr, Al, and Mn, and determined that formation of high molar mass and T g polymers required a pre-contact step between the catalyst and external nucleophilic co-catalyst. 25,28 Others have shown the importance of a pre-contact step between Cr catalysts and various co-catalysts.…”

“…23 Ko and co-workers were able to catalyze the synthesis of polycarbonates and cyclic carbonates using a variety of monomers with dinuclear Ni and Co complex catalytic systems, respectively. 24 Others have used Cr( iii ) catalysts for the ROCOP of epoxides such as CHO with PA. 25–27 Bester and co-workers used amino-bis(phenolate) Cr( iii ) complexes with 4-(dimethylamino)pyridine (DMAP) as a co-catalyst. 26 Boggioni used (salen)MCl catalysts, where M = Cr, Al, and Mn, and determined that formation of high molar mass and T g polymers required a pre-contact step between the catalyst and external nucleophilic co-catalyst.…”

Ring Opening Polymerization and Copolymerization for Polyester and Polycarbonate Formation by a Diamino-bis(phenolate) Chromium(III) Catalyst

“…24 Others have used Cr(III) catalysts for the ROCOP of https://doi.org/10.26434/chemrxiv-2023-sc5dl ORCID: https://orcid.org/0000-0001-8205-4130 Content not peer-reviewed by ChemRxiv. License: CC BY-NC-ND 4.0 epoxides such as CHO with PA. [25][26][27] Bester and co-workers used amino-bis(phenolate) Cr(III) complexes with 4-(dimethylamino)pyridine (DMAP) as a co-catalyst. 26 Boggioni used (salen)MCl catalysts, where M = Cr, Al, and Mn, and determined that formation of high molecular weight and Tg polymers required a pre-contact step between the catalyst and external nucleophilic co-catalyst was required.…”