Copolymerization of carbon dioxide and cyclohexene oxide with zinc/β-ketoiminato complexes:: Investigating the influence of the electron structure of zinc/β-ketoiminato complexes on the catalytic activity and resultant copolymer properties

A series of LZnX zinc/beta-ketoiminato complexes [L = CH3(OH)=C(CH2 CH=CH2)C)CH3)=NAr (L-1), CH3C(OH)=C(CH2CH2CN)C(CH3)=NAr (L-2), CH3C(OH)=C(CH2C6H5)C(CH3)=NAr (L-3), or CH3C(OH)=CHC(CH3)=NAr (L-4); Ar = 2,6-(Pr2C6H3)-Pr-i; and initiation group X = alcoholate or acetate (for L-1) or alcoholate (for L-2-L-4)] were synthesized, and their activities toward the copolymerization of carbon dioxide with cyclohexene oxide were determined. The 3-position substituents on the beta-ketoiminato ligand backbone of the zinc/beta-ketoiminato complexes played an important role not only in the catalytic activity but also in the intrinsic viscosity, chemical composition, and refined microstructure of the resultant copolymers. The order of the catalytic activity of L1ZnX with different initiation groups (X = OMe, (OPr)-Pr-i, or OAc) was L1Zn ((OPr)-Pr-i) > L1Zn (OMe) > L1Zn (OAc), being the opposite of the order of the leaving ability of the initiation groups. (c) 2006 Wiley Periodicals, Inc.