Thermally induced isomerization and decomposition of N-(2-aminoethyl)-1,3-propanediamine complexes of nickel(II) in the solid state

Abstract

[Ni(aepn) 2]X 2 · nH 2O, Ni(aepn)Y 2 · nH 2O and [Ni(aepn)Z 2] (where aepn is N-(2-aminoethyl)-1,3-propanediamine; n = 0 when X is Cl, Br, NO 3 and ClO 4; n = 4 when X or Y is 0.5SO 4 or 0.5SeO 4 and Z is Cl, Br and NO 3) have been synthesized and investigated thermally in the solid state. [Ni(aepn) 2]X 2 (X is 0.5SO 4 or 0.5SeO 4) undergoes exothermic irreversible phase transitions on heating (238–261°C and 220–244°C for [Ni(aepn) 2]SO 4 and [Ni(aepn) 2]SeO 4 respectively, Δ H = −7.3kJ mol −1 for [Ni(aepn) 2]SeO 4); and [Ni(aepn) 2](ClO 4) 2 shows an endothermic irreversible phase transformation on heating (228–240°C, Δ H = 4.2kJ mol −1). All the complexes possess octahedral geometry and the latter transformation is explained in terms of conformational changes of the individual chelate ring.