THERMAL INVESTIGATION AND STEREOCHEMICAL STUDIES OF SOME CYCLIC LIGAND COMPLEXES OF NICKEL(II), COPPER(II), ZINC(II) AND CADMIUM(II) IN THESOLID-STATE .1.

Nickel(II), copper(II), zinc(II), and cadmium(II) complexes of N-methy lmorpholine (Mmorph) and N,N'-dimethylpiperazine (DMP), with the compo sitions [Ni(Mmorph)Cl2], [2CuCl2.3Morph], [Zn(Mmorph)Cl2], [Ni(DMP)Cl2 ], [Cu(DMP)Cl2].H2O, [Zn(DMP)Cl2] and [Cd(DMP)Cl2], have been synthesi zed in order to carry out thermal investigations (TGA and DTA) and to study stereochemical changes during their thermal decomposition. Attem pts to prepare a methylmorpholine complex of CdCl2 failed. Some interm ediate complexes were isolated by the temperature arrest technique. Co nfigurational and conformational changes were studied from elemental a nd thermal analyses, IR spectral data, and magnetic moment measurement s. All the complexes of methylmorpholine and dimethylpiperazine appear ed to be tetrahedral, except [2CuCl2.3Morph] which is octahedral and d imeric. The activation energy E(a), and the enthalpy DELTAH and entro py DELTAS changes for the dehydration and decomposition reactions were evaluated with some standard equations and are compared. The order of stability of the complexes with respect to the activation energy is a lso discussed. A linear correlation is found between E(a) and DELTAS for the dehydration and decomposition reactions of the complexes.