Thermal studies of N,N′-diethylethane-1,2-diarnine complexes of nickel(II) in the solid state

Article abstract of DOI:10.1016/0040-6031(95)02664-9

NiL₂X₂·nH₂O (where L = N,N′-diethylethane-1,2-diamine; n = 2 when X is Cl^-, Br^-, I^-, NO₃^-, 0.5SO₄^2-, 0.5SeO₄^2- or CF₃SO₃^-; n = 0 when X is CF₃CO₂^- or CCl₃CO₂^-) have been synthesised from solution and investigated by TG-DTA and DSC in the solid state. All the hydrated complexes have trans octahedral geometry and on heating undergo dehydration-anation reactions. The dehydrated complexes are also trans octahedral, except NiL₂X₂ (X is NO₃^-, 0.5SO₄^2- or 0.5SeO₄^2-) for which cis octahedral geometry is proposed. [NiL₂(H₂O)₂]X₂ (X is Br^- or CF₃SO₃^-) shows thermochromism (blue → green) upon dehydration. NiL₂X₂ (X is Cl^-, Br^-, 0.5SO₄^2- or 0.5SeO₄^2-) yield mono-diamine species in the solid state on heating. NiL₂SO₄ undergoes a reversible phase transition (heating cycle, 178-193°C, ΔH = - 4.0k J mol^-1; cooling cycle, 186-172°C; ΔH = 4.0kJ mol^-1) without a visual colour change.