Co-polymerization of propylene oxide and CO2 using early transition metal (groups IV and V) metallocalix[n]arenes (n = 4, 6, 8)

Wang, Zhong Yu; Sun, Yong Chang; He, Zhen Hong; Xing, Tian; Wang, Zhong‐Yu; Sun, Yong‐Chang; He, Zhen‐Hong; Wang, Kuan; Liu, Zhao Tie; Elsegood, Mark R.J.; Bedwell, Elizabeth V.; Redshaw, Carl

Abstract

A number of metallocalix[n]arenes, where n = 4, 6, or 8, of titanium and vanadium have been screened for their ability to act as catalysts for the co‐polymerization of propylene oxide and CO2 to form cyclic/polycarbonates. The vanadium‐containing catalysts, namely [VO(L1Me)] (1), [(VO2)L2H6] (2), [Na(NCMe)6]2[(Na[VO]4L2)(Na(NCMe))3]2 (3), [VO(μ‐OH)L3/H2]2∙6CH2Cl2 (4), {[VO]2(μ‐O)L4[Na(NCMe)2]2} (5), {[V(Np‐tolyl)]2L4} (6) and [V(Np‐RC6H4)Cl3] (R = Cl (7), OMe (8), CF3 (9)), where L1H3 = methylether‐p‐tert‐butylcalix[4]areneH3, L2H8 = p‐tert‐butylcalix[8]areneH8, L3H4 = p‐tert‐butylthiacalix[4]areneH4, L4H6 = p‐tert‐butyltetrahomodioxacalix[6]areneH6, performed poorly, affording, in the majority of cases, TONs less than 1 at 90°C over 6 h and low molecular weight oligomeric products (Mn ≤ 1665). In the case of the titanocalix[8]arenes, {(TiX)2[TiX(NCMe)]2(μ3‐O)2(L2)} (X = Cl (10), Br (11), I (12)), which all adopt a similar, ladder‐type structure, the activity under the same conditions is somewhat higher (TONs >6) and follows the trend Cl > Br > I; by comparison the non‐calixarene species [TiCl4(THF)2] was virtually inactive. In the case of 10, it was observed that the use of PPNCl (bis[triphenylphosphine]iminium chloride) as co‐catalyst significantly improved both the polymer yield and molecular weight (Mn 3515). The molecular structures of the complexes [HNEt3]2[VO(μ‐O)L3H2]2∙3CH2Cl2 (4∙3CH2Cl2), [VO(μ‐OH)L3/H2]2∙6CH2Cl2 (4/) (where L3/H2 is a partially oxidized form of L3H4) and {(TiCl)2[TiCl(NCMe)]2(μ3‐O)2(L2)}·6.5MeCN (10·6.5MeCN) are reported.

Citation

Sun, Y. C., He, Z. H., Wang, Z. Y., Xing, T., Wang, Z., Sun, Y., He, Z., Wang, K., Liu, Z. T., Elsegood, M. R., Bedwell, E. V., & Redshaw, C. (in press). Co-polymerization of propylene oxide and CO2 using early transition metal (groups IV and V) metallocalix[n]arenes (n = 4, 6, 8). Journal of Applied Polymer Science, Article 50513. https://doi.org/10.1002/app.50513

• Journal Article Type: Article
• Acceptance Date: Jan 10, 2021
• Online Publication Date: Jan 26, 2021
• Deposit Date: Jan 26, 2021
• Publicly Available Date: Jan 27, 2022
• Journal: Journal of Applied Polymer Science
• Print ISSN: 0021-8995
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Article Number: 50513
• DOI: https://doi.org/10.1002/app.50513
• Keywords: Catalysts; Non‐polymeric materials and composites; X‐ray
• Public URL: https://hull-repository.worktribe.com/output/3700687
• Publisher URL: https://onlinelibrary.wiley.com/doi/10.1002/app.50513