Thermal reactions of N,N-Dimethyl-1,2-ethanediamine complexes of nickel (II) in the solid state

Abstract

Complexes [NiL₂(H₂O)X]X•nH₂O (L = N,N-dimethyl-1,2-ethanediamine; n = 0 when X = BF₄; n = 1 when X = Br; n = 3 when X = Cl), [NiL₂(H₂O)Y]•nH₂O (n = 2 when Y = SeO₄; n = 5 when Y = SO₄), [NiL₂(H₂O) ₂](NO₃)₂•H₂O and [NiL₂] (ClO₄)₂ have been synthesized and investigated thermally in the solid state. The complexes [NiL₂(H₂O)Cl]Cl•3H₂O, [NiL₂(H₂O)Br]Br•H₂O, [NiL₂(H₂O)(SO₂)]•5H₂O and [NiL₂(H₂O(SeO₄)]•2H₂O possess trans octahedral geometry and undergo deaquation-anation associated with trans→cis isomerization upon heating in the solid state whereas on deaquation the complex [NiL₂(H₂O) ₂](NO₃)₂•H₂O retains its trans octahedral configuration. The complex [NiL₂(H₂O)(BF₄)](BF₄) possesses cis octahedral geometry and on thermal deaquation it transforms to a square planar complex. The complex [NiL₂](ClO₄)₂ is square planar and undergoes a yellow → red thermochromic phase transition on heating (203–216°C; ΔH = 6.9 kJ mol⁻¹). The red isomer is also square planar. The species [NiLCl₂], [NiL(SO₄)] and NiL_0.33Cl₂ have been synthesized pyrolytically in the solid state from their corresponding parent diamine complexes. The complexes [NiLCl₂] and [NiL(SO₄)] possess octahedral geometry. NiL_0.33Cl₂ possesses an unusually high magnetic moment (4.1 BM at 28°C).