Synthesis, Structure of Zinc Complexes Containing Sulfonylated Binaphtholate Ligands and Their Catalytic Activities towards Ring‐Opening Polymerization of Lactide and ε‐Caprolactone

Abstract

Reaction of sulfonylated binaphthol [2-hydroxy-2'-tosyloxy-1,1-binaphthyl (1a, Ts-Binol) or 2-hydroxy-2'-(phenylsulfonyloxy)-1,1-binaphthyl (1b, Ps-Binol)] with 1 equiv. of ZnEt 2 afforded zinc complexes [(Ts-Binol)ZnEt] 2 (2a) and [(Ps-Binol)ZnEt] 2 (2b). Further reaction of zinc complexes 2a and 2b with benzyl alcohol (BnOH) gave the zinc benzyloxide [(Ts-Binol) 2 Zn 2 (OBn) 2 ] 2 (3a) and [(Ps-Binol) 2 Zn 2 (OBn)2] 2 (3b). Alternatively, the zinc benzyloxides 3a and 3b could also be obtained by reaction of compound 1a or 1b with Zn(OBn) 2 (in situ reaction of ZnEt 2 and BnOH). The complexes were fully characterized by elemental analyses and spectroscopic analyses, and complexes 2a, 2b and 3a were further characterized by single-crystal X-ray analyses. The catalytic activities of these zinc complexes towards ring-opening polymerization of ε-caprolactone and D,L-lactide were studied.