Thermal Studies of N-phenylethane-1,2-diamine Complexes of Nickel(II) in the Solid State

[NiL3]X2 (where L=N-phenylethane-1,2-diamine and X=I− and ClO4−), [NiL2X2] (X is Cl−, Br−, NCS−, 0.5SO42− or 0.5SeO42−) and [NiL2(H2O)2](NO3)2 have been synthesized from solution and their thermal study has been carried out in the solid phase. [NiL2Cl2] upon heating undergoes irreversible endothermic phase transition (142–152°C, ΔH=0.35 kJ mol−1) without showing any visual colour change. This phase transition is assumed to be due to conformation changes of the diamine chelate rings. NiLCl2 and NiL2.5I2 have been prepared pyrolytically from [NiL2Cl2] and [NiL3]I2 respectively in the solid state. [NiL2(H2O)2](NO3)2 upon heating undergoes deaquation-anation reaction without showing any visual colour change. [NiL2X2] (X is Cl−, Br−, NCS−), [NiL2(H2O)2](NO3)2 and [NiL2(NO3)2] possess trans-octahedral configuration, whereas, [NiL2X2] (X is 0.5SO42− or 0.5SeO42−) are having cis-octahedral configuration. Amongst the complexes, only NiLCl2 shows unusually high (5.1 BM at 27°C) magnetic susceptibility value.