Synthesis, structural features, and methyl methacrylate polymerisation of binuclear zinc(II) complexes with tetradentate pyrazolyl ligands

•The bispyrazole-containing binuclear and tetrahedral Zn(II) complexes are synthesized.•The Zn(II) complexes were active toward polymerization of MMA.•The activity increased by two-fold compared to the monomeric Zn(II) complex.

The reaction of ZnCl2 with ancillary ligands, including 1,4-bis-(N,N-di-(1H-pyrazolyl-1-methyl)amine)benzene (L1) and 4,4′-bis-(N,N-di(1H-pyrazolyl-1-methyl)phenyl)methane (L2), in ethanol yields Zn(II) chloride complexes, i.e., 1,4-bis-(N,N-di-(1H-pyrazolyl-1-methyl)amine)benzene(dichloro)Zn(II) [L1Zn2Cl4] and 4,4′-bis-(N,N-di-(1H-pyrazolyl-1-methyl)phenyl)methane(dichloro)Zn(II) [L2Zn2Cl4]. The X-ray crystal structures of Zn(II) complexes revealed that they are binuclear, and each zinc atom has a distorted tetrahedral geometry which involves a nitrogen atom from two pyrazole groups and two chloro ligands. The catalytic activity of [L1Zn2Cl4] and [L2Zn2Cl4] for the polymerisation of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) increased by twofold compared to the corresponding monomeric Zn(II) complex, N,N-bis(1H-pyrazolyl-1-methyl)aniline(dichloro)Zn(II) [LZnCl2], at 60 °C.

Graphical abstractThe bispyrazole-containing binuclear and tetrahedral zinc (II) complexes, [L1Zn2Cl4] and [L2Zn2Cl4] have been structurally characterised. The catalytic activity of Zn(II) complexes toward the polymerisation of MMA in the presence of MMAO increased by two-fold compared to the corresponding monomeric Zn(II) complex, [LZnCl2] at 60 °C.Figure optionsDownload full-size imageDownload as PowerPoint slide