Thermochemical and spectrophotometrical study of Ni(II) Complexes with Thiadiamines

Ni(II) complexes of some linear tridentates with one sulphur and two nitrogen donors have been studied in aqueous solution at 25°C in 0.5 M (K)NO 3 medium by means of the calorimetric and spectrophotometric technique. It is shown that the percentage facial isomer in the NiL 2+ complexes becomes more important with increasing substitution on the nitrogen or sulphur donor atoms. The NiL 2 2+ complexes most probably have a trans‐facial tetragonally distorted structure with four equatorially bound nitrogen donors and in axial position the sulphide donors. The same {Ni‐(N 4 S 2 )} 2+ cation was also present in the NiL 2 (NO 3 ) 2 solid state compounds.