Magnesium complexes incorporated by sulfonate phenoxide ligands as efficient catalysts for ring‐opening polymerization of ε‐caprolactone and trimethylene carbonate

Abstract

Two novel sulfonate phenol ligands—3,3′‐di‐tert‐butyl‐2′‐hydroxy‐5,5′,6,6′‐tetramethyl‐biphenyl‐2‐yl 4‐X‐benzenesulfonate (XCF3, LCF3‐H, and XOCH3, LOMe‐H)—were prepared through the sulfonylation of 3,3′‐di‐tert‐butyl‐5,5′,6,6′‐tetramethylbiphenyl‐2,2′‐diol with the corresponding 4‐substituted benzenesulfonyl chloride (1 equiv.) in the presence of excess triethylamine. Magnesium (Mg) complexes supported by sulfonate phenoxide ligands were synthesized and characterized structurally. The reaction of MgnBu2 with L‐H (2 equiv.) produces the four‐coordinated monomeric complexes (LCF3)2Mg (1) and (LOMe)2Mg (2). Complexes 1 and 2 are efficient catalysts for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and trimethylene carbonate (TMC) in the presence of 9‐anthracenemethanol; complex 1 catalyzes the polymerization of ε‐CL and TMC in a controlled manner, yielding polymers with the expected molecular weights and narrow polydispersity indices (PDIs). In ε‐CL polymerization, the activity of complex 1 is greater than that of complex 2, likely because of the greater Lewis acidity of Mg2+ metal caused by the electron‐withdrawing substitute trifluoromethyl (CF3) at the 4‐position of the benzenesulfonate group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3564–3572, 2010

Ring-opening polymerization of cyclic esters by phenoxy-thioether complexes derived from biocompatible metals

“…could be explained by considering that also the homoleptic complex 6 is a dimeric species, in which two of the four ligands bridge the two metallic centers. [38][39][40] The molecular mass estimated from DOSY experiments strongly supported this hypothesis (see Table 1).…”

Alkaline-Earth Metal Complexes in Homogeneous Polymerization Catalysis

“…Inspired by these results, Ko and coworkers subsequently obtained the directly related homoleptic, discrete complexes supported by biphenol-derived benzenesulfonate monoanionic ligands bearing a CF 3 (57) or a OMe (58) substituent in para position of the sulfonate aromatic ring [74] (Fig. 17).…”

Polymerization mechanism of trimethylene carbonate carried out with zinc(II) acetylacetonate monohydrate

“…Such initiators include, among others, zinc compounds. Obviously, compounds and complexes of this metal have been and are still the object of studies, as in many cases, they proved excellent initiators of polymerization and copolymerization of lactides, lactones, and cyclic carbonates 1–3. However, most often these are complexes with a complicated structure, difficult to synthesize, hygroscopic compounds, and easily undergo hydrolysis, and thus, highly problematic in practical and industrial applications.…”