Structural and Thermodiffractometric Analysis of Coordination Polymers. Part II:¹ Zinc and Cadmium Derivatives of the Bim ligand [Bim = Bis(1-imidazolyl)methane]

Abstract

New polynuclear coordination species containing the ditopic bis(1-imidazolyl)methane (Bim) ligand have been prepared as microcrystalline powders and structurally characterized by ab initio X-ray powder diffraction methods. [Zn(CH 3 COO) 2 (Bim)] n contains 1D chains with tetrahedral metal atoms bridged by Bim ligands; [CdBr 2 (Bim)] n shows a dense packing with hexacoordinated Cd(II) ions and μ-Br and μ-Bim bridges; at variance, the isomorphous [ZnCl 2 (Bim)] n and [ZnBr 2 (Bim)] n species contain cyclic dimers based on tetrahedral Zn(II) ions. Thermodiffractometric analysis allowed estimation of the linear thermal expansion coefficients and strain tensors derived there from. Bim-rich phases, with 2:1 ligand-to-metal ratio, were also isolated: ZnBr 2 (Bim) 2 (H 2 O) 3 and [Cd(CH 3 COO) 2 (Bim) 2 ] n containing cis and trans MN 4 O 2 chromophores, respectively, show 1D polymers built upon M 2 Bim 2 cycles, hinged on the metal ions. In all species the conformation of the Bim ligands is C s (or nearly so), while in the few sparse reports of similar coordination polymers the alternative C 2 one was preferentially observed.