Solid state thermal studies of nickel(II) diamine complexes

Abstract

The complexes [Ni(eten) 3]X 2·H 2O (eten = N-ethyl-1,2-ethanediamine; X = Cl, Br), [Ni(eten) 3]X 2 (X = BF 4, NO 3, 0.5SO 4, 0.5SeO 4), [Ni(eten) 2X 2·2H 2O (X = Cl, Br) and [Ni(meen) 3]X 2·2H 2O (meen = N-miethyl-1,2-ethanediamine; X = 0.5SO 4, 0.5SeO 4) have been synthesized from solution and their thermal investigation carried out in the solid state. [Ni(eten) 3]Br 2 [Ni(eten) 2X 2] (X = Cl, Br, 0.5SO 4, 0.5SeO 4), [Ni(eten)Cl 2], Ni(eten) 0.5Cl 2 and [Ni(meen) 2X 2] (X = 0.5SO 4, 0.5SeO 4) were isolated in the solid state from their corresponding parent complexes by a pyrolytic technique. Upon heating, [Ni(eten) 2X 2] (X = Cl, Br) and [Ni(eten) 3](BF 4) 2 undergo endothermic, kinetically irreversible phase transition, whereas [Ni(meen) 3]SeO 4 undergoes exothermic irreversible phase transition. The phase transition phenomena are assumed to be due to conformational changes in the diamine chelate rings. All the complexes except Ni(eten) 0.5Cl 2 have octahedral geometry. Ni(eten) 0.5 Cl 2 has an unusually high magnetic moment.