Preparation and Infrared Characterization of Thioborate Compounds and Polycrystals

Polycrystals and compounds in the series x Na₂S + (1 − x )B₂S₃ have been prepared for the first time in the range 0 x 0.75. Infrared spectroscopy has been used to examine the extent to which the structures of the thioborate systems are similar or dissimilar to their oxide analogues. The complexity of the IR spectra systematically increases and then decreases as the composition is changed away from and then up to another compound. This behavior is used to propose the existence of a new compound in the series, 2Na₂S · B₂S₃, sodium dithioborate. The other known compounds in this series, Na₂S · B₂S₃ and Na₂S · 3B₂S₃, were isolated in this same way. the IR spectra do not suggest the compound Na₂S · 2B₂S₃ forms. Evidence is found, however, for the formation of tetrahedral borons, isolated thioboroxyl rings, and orthoborate triangles. These results are used to conclude that there are significant similarities between the structures and compounds that form in the alkali thioborate and borate systems.