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Issue 42, 2014
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Novel (cyanamide)ZnII complexes and zinc(II)-mediated hydration of the cyanamide ligands

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The cyanamides NCNR2 (R2 = Me2, Ph2, C5H10) react with ZnX2 (X = Cl, Br, I) in a 2 : 1 molar ratio at RT, giving a family of zinc(II) complexes [ZnX2(NCNR2)2] (R2 = Me2, X = Cl 1, X = Br 2, X = I 3; R2 = C5H10, X = Cl 4, X = Br 5; X = I 6; R2 = Ph2, X = Cl 7, X = Br 8, X = I 9; 75–92% yields). Complexes 7 and 8 undergo ligand redistribution in wet CH2Cl2 solutions giving the [Zn(NCNPh2)4(H2O)2][Zn2(μ-X)2X4] (X = Cl 10, Br 11) species that were characterized by 1H NMR, HRESI-MS, and X-ray diffraction. Halide abstraction from 1–3 by the action of AgCF3SO3 or treatment of Zn(CF3SO3)2 with NCNR2 (R2 = Me2, C5H10) leads to labile complexes [Zn(CF3SO3)2(NCNR2)3] (R2 = Me2, 12; C5H10, 13). Crystallization of 12 from wet CH2Cl2 or from the reaction mixture gave [Zn(NCNMe2)3(H2O)2](SO3CF3)2 (12a) or [Zn(CF3SO3)2(NCNMe2)2] (12b), whose structures were determined by X-ray diffraction. The ZnII-mediated hydration was observed for the systems comprising ZnX2 (X = Cl, Br, I), 2 equiv. NCNR2 (R2 = Me2, C5H10, Ph2) and ca. 40-fold excess of water and conducted in acetone at 60 °C (R2 = Me2, C5H10) or 80 °C (R2 = Ph2) in closed vials, and it gives the urea complexes [ZnX2{OC(NR2)NH2}] (R2 = Me2, X = Cl 13, X = Br 14, X = I 15; R = C5H10, X = Cl 16, X = Br 17; X = I 18; R2 = Ph2, X = Cl 19, X = Br 20, X = I 21; 57–81%). In contrast to the ZnII-mediated hydration of conventional nitriles, which proceeds only in the presence of co-catalyzing oximes or carboxamides, the reaction with cyanamides does not require any co-catalyst. Complexes 1–9, 12–19 were characterized by 1H, 13C{1H} NMR, IR, HRESI-MS, and X-ray crystallography (for 1–3, 8, 9, 13–15, and 17), whereas 20 and 21 were characterized by HRESI+-MS and 1H and 13C{1H} NMR (for 20). The structural features of the cyanamide complexes 1, 2, 7, and 8 were interpreted by theoretical calculations at the DFT level.

Graphical abstract: Novel (cyanamide)ZnII complexes and zinc(ii)-mediated hydration of the cyanamide ligands

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The article was received on 17 Jun 2014, accepted on 22 Aug 2014 and first published on 22 Aug 2014

Article type: Paper
DOI: 10.1039/C4DT01812E
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Citation: Dalton Trans., 2014,43, 15798-15811
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    Novel (cyanamide)ZnII complexes and zinc(II)-mediated hydration of the cyanamide ligands

    A. S. Smirnov, E. S. Butukhanova, N. A. Bokach, G. L. Starova, V. V. Gurzhiy, M. L. Kuznetsov and V. Yu. Kukushkin, Dalton Trans., 2014, 43, 15798
    DOI: 10.1039/C4DT01812E

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