THERMAL-DECOMPOSITION REACTIONS OF NICKEL(II) COMPLEXES UNDER QUASI-EQUILIBRIUM CONDITIONS .6. THERMOCHEMICAL INVESTIGATION OF NICKEL(II)-NICOTINAMIDE-SOLVENT INTERACTIONS IN SOLID HALOGENO AND THIOCYANATO COMPLEXES

Stoichiometries of thermal decompositions have been studied for the fo llowing Ni(II) nicotinamide (NA) complexes: Ni(NA)(2)Cl-2 . 2H(2)O (I) , Ni(NA)(3)Br-2 . 4H(2)O (II), Ni(NA)(4)I-2 . 4H(2)O (III) and Ni(NA)( 4) (NCS)(2) . 2C(2)H(5)OH (IV). Heating the compounds first results in a release of solvent molecules and desolvated compounds I'-IV' are fo rmed. NA molecules are released in two steps for complexes I', II', an d III', and in one step for complex IV'. Magnetic and spectral propert ies, as well as thermochemical data (quasi-equilibrium decomposition t emperatures, DSC data) indicate an octahedral monomeric structure for complexes III, IV, III' and IV', and a polymeric structure for complex es I,II,I' and II', with adsorbed (I) and crystal water (II, III) or e thanol (IV).