Niobium chalcogenide halides

Although not yet published in a journal, according to thesis work, the vanadium compounds VSCl (11), VSBr, and VSI (208) seem to exist. Numerous niobium chalcogenide halides have been reported, and among these are the best characterized examples of Group VB (see Table X). Only two tantalum compounds, TaSjCU (361) and TaSCls (13) have thus far been described in the literature. 

Just as, in Group VB, niobium, so, in this Group, molybdenum provides most of the examples of the chalcogenide halides. The occurrence and preparation of such compounds are described in numerous publications. In most cases, they have been obtained as powders, with the composition based on chemical analyses only. The presence of defined, homogeneous phases is, therefore, in many cases doubtful. In addition, some published results are contradictory. A decision is possible where a complete structure analysis has been made. As will be shown later, the formation of metal-metal bonds (so-called clusters), as in the case of niobium, is the most characteristic building-principle. Such clusters... 

The alkali metal rhenium- and technetium chalcogenide clusters described in Section 5.6 are also octahedral.These clusters have M6Es units with eight face-capping anions on the octahedral faces in contrast to the niobium halide or oxide clusters. The A4M6S14 (A = alkali metal, M — Re, Tc), Cs6Rc6Si2, and... 

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