Thermal studies of bis(2-aminoethyl)methylamine complexes of nickel(II) inthe solid state

[NiL2]X-2. nH(2)O (where L is bis(2-aminoethyl)methylamine, and n = 0 when X is Cl-, Br-, SCN- and CF3COO-, n = 3 when X is 0.5SO(4)(2-) and 0.5SeO(4) (2-)) and NiLX2. nH(2)O (n = 0 when X is Cl-, Br-, NO3-, n = 1 when X is CF 3COO(-) and n = 3 when X is 0.5SO(4)(2-) and 0.5SeO(4)(2-)) have been synth esized and investigated thermally in the solid state. All the bis, as well as monotriamine complexes possess octahedral geometry. [NiI2](SCN)(2) upon heating undergoes irreversible phase transition (155-180 degrees C; Delta H = 5.6 kJ mol(-1)) yielding an isomeric species which on further heating sh ows reversible phase transition (182-205 degrees C for heating, Delta H = 2 .8 kJ mol(-1); 170-200 degrees C for cooling, Delta H = -2.8 kJ mol(-1)) an d [NiL2]SO3. 3H(2)O undergoes an endothermic phase transition after deaquat ion 172-200 degrees C; Delta H = 6.8 kJ mol(-1)). Nil(NO3)(2) also shows a phase transition (195-220 degrees C; Delta H = 8.9 kJ mol(-1)). The phase t ransitions are proposed to be due to the conformational change in the chela te rings of the triamine. NiLAO(4). 3H(2)O (A = S or Se) exhibit thermochro mism, blue-to-greenish-blue for elimination of two molecules of water and g reenish-blue-to-light-green for elimination of the residual water molecule. The effect of methyl substitution in N-2-position of bis(2-aminoethyl)amin e is not noticeable with respect to thermal stability of the complexes, but is pronounced in the case of thermally induced solid-state isomerization. (C) 1999 Elsevier Science B.V. All rights reserved.