Metal Ion and Metal‐to‐Ligand Ratio Regulated Construction of Cu(II) and Co(II) Coordination Polymers as Efficient Catalysts for Ring‐Opening Polymerization of L‐Lactide

Abstract

Three new coordination polymers (CPs), {[Cu(NDC)(Fbtx)(H2O)]·1.5H2O}n (1), {[Co(NDC)(Fbtx)(H2O)2]·0.5Fbtx}n (2), and [Co2(NDC)2(Fbtx)]n (3), were synthesized by employing acid‐base mixed ligands of rigid 1,4‐naphthalenedicarboxylic acid (H2NDC) and flexible bis(1,2,4‐triazole‐1‐ylmethyl)‐2,3,5,6‐tetrafluorobenzene (Fbtx) under both hydrothermal and microwave‐assisted reaction conditions. Single‐crystal structure analysis establishted that both compounds 1 and 2 exhibit two‐dimensional (2D) layered structures, while compound 3 features a three‐dimensional (3D) complicated framework. The geometries of metal ions vary from square pyramidal (in 1 and 3) to distorted octahedral (in 2). Topological strudy showed that compounds 1 and 2 have exposed common 4‐connected 44‐sql net, while compound 3 has made a novel 4,5‐connected net with point symbol of (43·62·7)(43·64·72·8). The catalytic performance of the three complexes for the solvent‐free ring‐opening polymerization of L‐lactide has been investigated. The results indicated that compound 3 with coordinatively unsaturated cobalt(II) sites showed very high activity and the molecular weight of the polymer obtained was also high. Moreover, the complex 3 catalyst could be recycled up to five times with the retention of both catalytic activity and crystal structure.