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Dalton transactions (Cambridge, England : 2003)

Novel (cyanamide)Zn(II) complexes and zinc(ii)-mediated hydration of the cyanamide ligands.


PMID 25220287

Abstract

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 , X = Br , X = I ; R2 = C5H10, X = Cl , X = Br ; X = I ; R2 = Ph2, X = Cl , X = Br , X = I ; 75-92% yields). Complexes and undergo ligand redistribution in wet CH2Cl2 solutions giving the [Zn(NCNPh2)4(H2O)2][Zn2(μ-X)2X4] (X = Cl , Br ) species that were characterized by (1)H NMR, HRESI-MS, and X-ray diffraction. Halide abstraction from 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, ; C5H10, ). Crystallization of from wet CH2Cl2 or from the reaction mixture gave [Zn(NCNMe2)3(H2O)2](SO3CF3)2 () or [Zn(CF3SO3)2(NCNMe2)2]∞ (), whose structures were determined by X-ray diffraction. The Zn(II)-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 , X = Br , X = I ; R = C5H10, X = Cl , X = Br ; X = I ; R2 = Ph2, X = Cl , X = Br , X = I ; 57-81%). In contrast to the Zn(II)-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 , were characterized by (1)H, (13)C{(1)H} NMR, IR, HRESI-MS, and X-ray crystallography (for , , , , and ), whereas and were characterized by HRESI(+)-MS and (1)H and (13)C{(1)H} NMR (for ). The structural features of the cyanamide complexes , , , and were interpreted by theoretical calculations at the DFT level.