Solid state thermal studies of nickel (II) diamine complexes

Abstract

The complexes [Ni(eten)₃]X₂•H₂O (eten = N-ethyl-1,2-ethanediamine; X = Cl, Br), [Ni(eten)₃]X₂ (X = BF₄, NO₃, 0.5SO₄, 0.5SeO₄), [Ni(eten)₂X₂•2H₂O (X = Cl, Br) and [Ni(meen) ₃]X₂•2H₂O (meen = N-miethyl-1,2-ethanediamine; X = 0.5SO₄, 0.5SeO₄) have been synthesized from solution and their thermal investigation carried out in the solid state. [Ni(eten)₃]Br₂ [Ni(eten)₂X₂] (X = Cl, Br, 0.5SO₄, 0.5SeO₄), [Ni(eten)Cl₂], Ni(eten)_0.5Cl₂ and [Ni(meen)₂X₂] (X = 0.5SO₄, 0.5SeO₄) were isolated in the solid state from their corresponding parent complexes by a pyrolytic technique. Upon heating, [Ni(eten)₂X₂] (X = Cl, Br) and [Ni(eten) ₃](BF₄)₂ undergo endothermic, kinetically irreversible phase transition, whereas [Ni(meen)₃]SeO₄ 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)_0.5Cl₂ have octahedral geometry. Ni(eten)_0.5Cl₂ has an unusually high magnetic moment.