Study on Catalytic Activity of Synthetic Cobalt, Nickel and Copper Complexes due to Preferred Structures Determined by X‐Ray Crystallography for Methyl Methacrylate Polymerization

Abstract

We have designed and synthesized two novel pyridyl‐quinoxaline ligands, L1 and L2, as well as twelve cobalt, nickel, and copper complexes, 1–6 and 1 a–6 a. Unexpectedly, high regularities in the synthesis of both ligands and complexes were found. Further X‐ray diffraction analyses revealed that the two ligands had similar geometrical configurations, and the structures of twelve complexes were regularly divided into two categories: binuclear and mononuclear, which would be beneficial for elucidating structure‐activity relationships of metal catalysts. In addition, the experimental results showed significant variations in the catalytic performance of methyl methacrylate polymerization with different catalysts. Under the optimum reaction conditions, the mononuclear copper complex 3 a displayed a remarkably high catalytic activity of 2.76×105 g ⋅ mol−1 h−1, generating Poly(methyl methacrylate) with molecular weight of Mn=8.55×105 g ⋅ mol−1 and molecular weight distribution of Đ=1.67.This outcome suggested that copper had the potential to serve as a promising catalytic metal center.