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

摘要

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(CH3-COO)2(Bim)]_n contains 1D chains with tetrahedral metal atoms bridged by Bim ligands;[CdBr2(Bim)]_n shows a dense packing with hexacoordinated Cd(II) ions and mu-Br and mu-Bim bridges;at variance,the isomorphous [ZnCI2-(Bim)]_n and [ZnBr2(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:ZnBr2(Bim)2(H2O)3 and [Cd(CH3COO)2(Bim)_2]_n containing cis and trans MN4O2 chromophores,respectively,show 1D polymers built upon M2Bim2 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.