Synthesis, characterization, and catalytic behavior of copper complexes with fluorosubstituted β‐ketoimine ligands

Abstract

ABSTRACT A series of β‐ketoimine ligands with various fluorine substitutions on the N ‐aryl ring and the corresponding copper complexes were synthesized. The fluorosubstituents exerted significant effects on the structures and catalytic activities of the copper complexes. X‐ray diffraction revealed that the copper(II) central ions were coordinated by two trans‐oriented β‐ketoimino ligands with delocalized double bonds. Complex 2b (with mono‐ o ‐fluorosubstitution on the N ‐aryl moiety) adopted a central symmetric square planar structure, whereas complex 2f (with bis‐ o ‐fluorosubstitution) had a distorted square planar structure with a dihedral angle of 28.2°. The CuN bond length in 2f was appreciably shorter than that in 2b . When activated by modified methylaluminoxane, the copper complexes effectively polymerized methyl acrylate. Furthermore, substitution with more fluorine atoms resulted in a higher activity. The catalytic activity of the pentafluorosubstituted complex 2h reached 57.5 kg (mol of Cu) −1 ·h −1 under optimized conditions; this was the highest value reported up to this point for copper complexes in acrylic monomer polymerization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131 , 41178.