Synthesis and Pyrolytical Solid‐Phase Structural Transformations of New Oxorhenium(V) Complexes with 2‐Benzoxazolethione

Abstract

Abstract2‐Benzoxazolethione reacts with the parent oxorhenium(V) complex, H2[ReOCl5], to yield either mononuclear or dinuclear complexes depending on the metal: ligand molar ratio and the concentration of hydrochloric acid containing the parent rhenium complex. The mononuclear complexs [ReOLCl(OH2)3]Cl2, [ReOL2(OH2)3]Cl3 and [ReOLCl3(OH2)]; and dinuclear complexes [Re2O3(μ‐L)2Cl4]·2H2O and [Re2O2(μ‐L)L2Cl6]‐2H2O were obtained. Both types of complexes have octahedral configurations. The mononuclear complexes prepared in 6N HCl or in 9N HCl undergo irreversible one‐step solid‐phase thermochromism transformation, thus, the colour of complexes changed from green to brown, black or bluish‐green, upon heating. For the complexes obtained in 6N HCl, this step corresponds to structural changes due to the formation of other types of dinuclear complexes, while the mononuclear complex obtained in 9N HCl changes to another mononuclear complex with different coordination sites. On the other hand, the colour of the dinuclear complexes prepared in 2N HCl changed from brown to black, upon heating, in one step solid‐phase thermochromism transformation corresponding to a change in the mode of coordination sites of the organic ligand. All thermal products obtained have octahedral configurations. The ligand behaves in these complexes either as a neutral, mono‐, bidentate or monoanionic bidentate towards the oxorhenium ions. All complexes and the corresponding thermal products were isolated and their structures were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, 1H NMR and TG‐DTA measurements as well as by mass spectroscopy.