Synthesis, crystal structure and DFT calculations of a cyanido-bridged dinuclear zinc(II) complex of cis-1,2-diaminocyclohexane (Dach) containing a dinuclear cyanidozincate(II) anion, [Zn_2(Dach)_4(CN)] [Zn_2(CN)_7]·2CH_3OH

摘要

A zinc(II)-cyanide complex of cis-1,2-diaminocyclohexane (Dach) containing two dinuclear units, [Zn_2(Dach)_4(CN)][Zn_2(CN)_7]·2CH_3OH (1) was prepared and characterized by IR and NMR spectroscopy as well as by single crystal X-ray crystallography. Complex 1 is composed of two dinuclear ionic units, cationic [Zn_2(Dach)_4(CN)]~(3+) and anionic [Zn_2(CN)_7]~(3-) and two non-coordinating molecules of methanol. The Zn atoms in [Zn_2(Dach)_4(CN)]~(3+) cation adopt a square-pyramidal environment with CN ligand occupying the apical position, while the Zn atoms in [Zn_2(CN)_7]~(3-) anion exhibit a tetrahedral geometry. The dinuclear units are associated to each other through hydrogen bonding interactions to form a three dimensional network in the solid state. The presence of, a band around 2200 cm~(-1) in IR spectrum and a resonance at 140 ppm in ~(13)C NMR indicated the presence of cyanide in the complex. The structures of 1 and two of its analogues, [Zn(Dach)(CN)_2]_4 (2) and {[Zn(Dach)_2][Zn(CN)_4]}_2 (3) were predicted using theoretical (DFT) method. The DFT calculated values of the Gibbs free energies of the model complexes reveal that 1 is more stable than the analogous predicted complexes, 2 and 3 by 5.16 and 3.47 kcal mol~(-1), respectively.