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, [Zn2(Dach)4(CN)][Zn2(CN)7]·2CH3OH

Publication date: 5 October 2018
Source:Journal of Molecular Structure, Volume 1169
Author(s): Muhammad Monim-ul-Mehboob, Tobias Rüffer, Heinrich Lang, Wiktor Zierkiewicz, Abdul Rauf, Muhammad Amin, Anvarhusein A. Isab, Omar Ajouyed, Saeed Ahmad
A zinc(II)-cyanide complex of cis-1,2-diaminocyclohexane (Dach) containing two dinuclear units, [Zn2(Dach)4(CN)][Zn2(CN)7]·2CH3OH (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 [Zn2(Dach)4(CN)]³⁺ and anionic [Zn2(CN)7]^3- and two non-coordinating molecules of methanol. The Zn atoms in [Zn2(Dach)4(CN)]³⁺ cation adopt a square-pyramidal environment with CN ligand occupying the apical position, while the Zn atoms in [Zn2(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 ¹³C 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.

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