Cadmium(II) complexes containing N′-substituted N,N-bispyrazolyl ligands: The formation of 4- and 5-coordinated monomers versus 6-coordinated dimer

Novel Cd(II) bromide complexes [LaCdBr2], [LbCdBr2] and [LcCd(μ-Br)Br]2 have been synthesized and characterized. [LaCdBr2] and [LbCdBr2] were distorted tetrahedral and trigonal bipyramidal geometry around metal, respectively, depending on the coordination of the nitrogen atom of N′-substituted amine moiety and the cadmium center. However, [LcCd(μ-Br)Br]2 reveals a bromo-bridged 6-coordinated dimeric species. Specifically, the catalytic activity of [LbCdBr2] (1.13 × 105 g PMMA/mol Cd·h) in the polymerization of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) at 60 °C was higher than that of [LaCdBr2] (5.03 × 104 g PMMA/mol Cd·h) and reference complex [CdCl2] (3.53 × 104 g PMMA/mol Cd·h).