Synthesis, characterisation and solid state thermal behaviour of nickel (II) diamine complexes

[NiL2X2] (L = N,N′-dimethyl-1,2-ethanediamine; X = Cl−, CF3CO2−, CC13CO2− and CBr3CO2−), [NiL2C2O4] • H2O and [NiL2X2] • 2 H2O (X = Br−, 0.5 SO42− and 0.5 SeO4−) have been synthesised and their thermal studies carried out. Thermally induced phase transition phenomena are noticed in [NiL2X2] (X = CF3CO2− and CCl3CO2−) and their probable mechanisms are described. [NiL2X2] (X = Br−, 0.5 SO42− and 0.5 SeO42−) and [NiLX2] (X = Cl−, 0.5 C2O42− and 0.5 SO42−) have been prepared by solid state pyrolysis from the respective parent diamine complexes. [NiL2X2] have been made in solid state by temperature arrest technique from [NiL2 (CX3CO2)2] (X = Cl− and Br−)