A THERMOANALYTICAL APPROACH TO THE INTERPRETATION OF THE PROPOSED ISOMERISM OF SOME NICKEL(II) BENZIMIDAZOLE COMPLEXES

The proposed isomerism of some NiL4Cl2 complexes where L is benzimidazole, is investigated by thermoanalytical techniques coupled with an FT-IR system and supported by spectroscopic techniques. The proposed compounds, unsolvated NiL4Cl2 (two isomers), acetone-solvated NiL4Cl2S and NiL4Cl2S2 (three isomers), where S is aceton, appear to be the same compounds at different solvation levels, where water takes part in the solvation process for one of the six compounds. Reflectance and IR spectra were obtained at room temperature. Analysis of the data obtained supports the hypothesis that two possible main structures are present: (i) a distorted, octahedral, dimeric cationic structure where one chloride acts as a bridge between two nickel ions, the planar field being occupied by four benzimidazole neutral molecules; (ii) a distorted, octahedral, monomeric neutral structure where two chlorides are in both axial sites. The dimeric cationic structure changes to the monomeric neutral structure by a temperature-induced anation reaction, as demonstrated by an exothermic process at 145-degrees-C. The interaction of acetone with the complexes described is also discussed and a new thermal procedure is suggested for obtaining some of the compounds investigated.