ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Isomerism of octahedral thiosemicarbazide nickel(II) complexes

A. Sirota, T. Šramko, and J. Gažo

Department of Inorganic Chemistry, Slovak Technical University, SSO 37 Bratislava

Abstract: Solid nickel(II) complexes with thiosemicarbazide, CH₅N₃S (tsc), of the type [Ni(tsc)₃]X₂ were prepared, X being NO₃ (monohydrate and anhydrous), CI (anhydrous), Br^-(anhydrous), I^- (dihydrate and anhydrous   α and ß isomer), and СlO₄ (dihydrate and anhydrous). Their spectral, magnetic, and thermal properties were investigated. The above complexes are paramagnetic and show electronic absorption spectra typical of octahedral nickel(II) complexes. Thiosemicarbazide molecules were proved to be bidentate ligands, forming NiN₃S₃ environment around the central atom. Infrared absorption spectra allowed to separate the complexes under investigatio into two groups: 1. nitrates, Perchlorates, and iodides (dihydrate and anhydrous a isomer), 2. anhydrous chloride, bromide, and iodide (ß isomer). Differences found in electronic absorption spectra were in good agreement with those observed in infrared spectra. Splitting of absorption bands as well as the crystal structure analysis results known for [Ni(tsc)₃](NO₃)₂ . H₂O and [Ni(tsc)₃](N0₃)₂, make it possible to come to the conclusion that the complexes of the first group have 1,2,3-arrangement of ligands (cis), while those of the second group are most probably trans isomers with 1,2,6-arrangement. The anhydrous α  and ß forms of iodide (green or blue, respectively) are considered to be geometrical isomers. Method for preparation of both isomers and their mutual interconversions are given in the present paper. It has been found that the ß isomer is thermodynamically more stable.

Full paper in Portable Document Format: 301a90.pdf

Chemical Papers 30 (1) 90–99 (1976)