Synthesis, characterization and crystal structures of Cd(II) and Zn(II) complexes with 2,2′-biimidazole |
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| Authors: | Letitia M Gruia André L Beauchamp |
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| Institution: | a Département de Chimie, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Que., Canada H3C 3J7
b Département de Chimie, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, Que., Canada H3C 3P8 |
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| Abstract: | The reactions of zinc and cadmium salts with 2,2′-biimidazole (H2biim) yielded a series of compounds in which the ligand is coordinated in the chelating bidentate mode. ZnCl2 and Ag(H2biim)](NO3) in methanol in a 2:1 proportion produced Zn(H2biim)Cl2, in which the metal has a distorted tetrahedral coordination. A 1:2 ratio led to Zn(H2biim)2(CH3OH)2](NO3)2, containing an octahedrally coordinated Zn(II) center with the O-bonded methanol ligands occupying trans positions. The corresponding Cd(H2biim)2(CH3OH)2](NO3)2 compound was obtained from CdCl2. By starting with Cd(NO3)2 and Cd(ClO4)2 in aqueous media, the related octahedral bis-chelate compounds Cd(H2biim)2(NO3)(H2O)](NO3) and Cd(H2biim)2(ClO4)2, respectively, were isolated, the apical positions being filled by perchlorate oxygens in the latter case. With Cd(BF4)2, the glass container participated in the reaction and a tris-chelate complex Cd(H2biim)3]2(SiF6)(BF4)2 · 6EtOH was isolated. The Cd(H2biim)3]2+ and  ions define an extended hydrogen-bonded network, in which  ions surrounded by disordered ethanol molecules occupy large cavities. The two free N-H groups provide H2biim with a unique ability to form hydrogen bonds and their interactions with counter anions or other acceptors play a determining role in controlling molecular packing. The IR spectra of all compounds are discussed. |
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| Keywords: | Zinc Cadmium Biimidazole Supramolecular Crystal structure IR Hydrogen bonding |
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