Muhammad Yusuf, Nova Pratiwi Indriyani, Arifin, Aditya Wibawa Sakti, Hiromi Nakai, I. Made Arcana, Muhamad Abdulkadir Martoprawiro, Yessi Permana
A series of zirconium β-diketonates, i.e., tris(acetylacetonato)zirconium(IV) chloride (1), tris(benzoylacetonato)zirconium(IV) chloride (2), tris(dibenzoylmethanato)zirconium(IV) chloride (3), and tris(benzoyltrifluoroacetonato)zirconium(IV) chloride (4) work as efficient catalysts in the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) to generate poly(ε-CL) with repeating unit up to 68. The activity of the complexes was in the order of 2 > 4 > 1 > 3, with more Lewis acidic complexes 2 and 4 gave higher catalytic activity. DFT calculations showed that a trifluoromethyl moiety in the ligand decreases the oxygen nucleophilicity at intermediate complexes, and thus inhibiting the propagation process. Three possible states of the complex before ε-CL coordination in the ROP were proposed as follows: (i) dissociation of one ligand; (ii) dissociation of one coordinated-oxygen of the ligand from zirconium and (iii) direct insertion of sp2-oxygen of ε-CL into Zr (no change of the complex geometry). The thermodynamic analysis via the Gibbs energy calculations at DFT level revealed that a direct insertion of sp2-oxygen of ε-CL into zirconium is the most plausible pathway for the ROP. © 2023 Elsevier B.V.
Department of Chemistry, Universitas Negeri Medan, Jl. Willem Iskandar, Medan, 20221, Indonesia; Inorganic & Physical Chemistry Research Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung, 40132, Indonesia; Institute of Transformative Bio-Molecules, Nagoya University, 464-8602, Japan; Global Center for Science and Engineering, Waseda University, 169-8555, Japan; Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 189-8555, Japan; Waseda Research Institute for Science and Engineering, Waseda University, 189-8555, Japan
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