Synthesis and structural characterisation of tetrahedral zinc(II) and trigonal bipyramidal cadmium(II) complexes containing N′-cyclohexyl substituted N,N-bispyrazolyl ligand

The bis(pyrazolyl)-based ligands L¹ and L², where L¹ is N,N-bis((1H-pyrazol-1-yl)methyl)cyclohexanamine and L² is N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)cyclohexanamine, reacted with [ZnCl₂] and [CdBr₂·4H₂O], respectively, and resulted in mononuclear [LⁿMX₂] (Lⁿ = L¹ and L²; M = Zn, X = Cl; M = Cd, X = Br) complexes in a facile yield and high purity. The synthesised complexes were characterised spectroscopically and X-ray crystallographically. The molecular structure of 4-coordinate [L¹ZnCl₂] was best described as a distorted tetrahedral, whereas 5-coordinate [L¹CdBr₂] and [L²CdBr₂] exhibited distorted trigonal bipyramidal geometry involving the metal centres. [L¹ZnCl₂] showed the highest catalytic activity for the polymerisation of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) with an activity of 4.40 × 10⁴ g PMMA/molZn h at 60°C and resulted in syndiotactic poly(methylmethacrylate) (PMMA).