[NiL2(H2O)2]X2 (L = N,N'-dipropyl-1,2-ethanediamine; X = Cl-, Br-, I-, CF3CO2-, CF3SO3-), [NiL2(NCS)2], [NiL'Cl2] and [NiL'(CF3CO2)2(H2O) 2]· 2H2O (L'=N,N'-diisopropyl-1,2-ethanediamine) have been synthesized from solution and characterized. NiLCl2 has been prepared in the solid state from its parent species by the temperature arrest technique. Upon heating, [NiL2(H2O)2]X2 undergoes deaquation, followed by anion coordination with a change in color: blue-violet to sky blue when X is Cl- and Br-; blue-violet to green when X is I-; and blue-violet to greenish blue when X is CF3CO2- and CF3SO3-. [NiL2X2] revert in two steps; the larger the size of X the lower is the rate of reversion. All the bis-species upon further heating decompose straightaway to unidentified end products with the exception of [NiL2Cl2] and [NiL2Br2], which yield mono diamine species. [NiL2(NCS)2] upon heating exhibits an irreversible endothermic phase transition (82-180°C; ?H= 8.1 kJ mol-1) without showing any visual color change. The configuration of the complexes [NiL2(H2O)2]X2 and [NiL2X2] is proposed to be trans-octahedral on the basis of the electronic spectra in the NIR region. [NiL2(NCS)2] crystallizes in the monoclinic space group P21/c with a = 9.2461(9), b = 9.2633(5), c = 14.4650(8) Å, ß = 92.082(5) and Z = 2. The complex possesses slightly distorted trans-octahedral geometry. [NiL'Cl2] and [NiL'(CF3CO2)2(H2O) 2]·2H2O upon heating decompose without showing any phase transition. © Acta Chemica Scandinavica 1998.
|Number of pages||7|
|Journal||Acta Chemica Scandinavica (1989)|
|Publication status||Published - Jun 1998|