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

•[LnCdBr2]m (Ln = L1, L2, L3, m = 1, 2) with N’-substituted N,N-bispyrazolyl are reported.•The molecular structures of [LnCdBr2]m were determined.•[LnCdBr2]m proved to be active for MMA polymerisation with syndiotacticity of ca. 0.70.

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).

Graphical abstractNovel Cd(II) bromide complexes [LaCdBr2], [LbCdBr2], and [LcCd(µ–Br)Br]2 have been synthesized. [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.Figure optionsDownload full-size imageDownload as PowerPoint slide