Niobium halide complexes

In addition to their applications in organic synthesis, all of the niobium halide complexes described here serve as convenient precursors to a variety of known coordination complexes of niobium(III) and (IV) as well as organo-metallic compounds. ... 

Ligand Exchange in Metal Halide Clusters. Rhenium, molybdenum, tantalum and niobium halides are high-valence metal clusters that formally behave as Lewis acids towards halide ions forming anionic complexes that retain the structure of the original cluster. 

The reactions of 1,2,5-triphenylphosphole (tpp)(46), 1,2,5-triphenylphosphole oxide (tppO), sulphide (tppS), and selenide (tppSe), with niobium(v) and tan-talum(v) halides in dry, oxygen-free organic solvents have been studied. The complexes formed were characterized by i.r. and X-ray spectroscopy. The... 

A further identification of the niobium (IV) halide-pyridine complexes was provided by x-ray powder pattern data, as shown in Table V. The values obtained from these measurements corresponded closely to those found for NbBr4 py2 and NbCl4 py2 (12). 

Niobium(III) halides are known, notably the chloride, NiCl3. which is of particular interest because its solution has been shown to contain Nb + ions (in equilibrium with NbCl, 3- complex 10ns),... 

Hala, J. Halides, Oxyhalides and Salts of Halogen Complexes of Titanium, Zirconium, Hafnium, Vanadium, Niobium and Tantalum, Vol, 40, Elsevier Science, New York, NY, 1989. 

In addition to the bimetallic complexes of rhenium and alkaline metals formed as byproducts in the exchange reactions of rhenium halids with alkali alkoxides (such as, for example, LiReO(OPr )5 xLiCl(THF)2 [519]) there has been recently prepared a number ofbimetallic complexes ofrhenium and molybdenum, rhenium and tungsten, and rhenium and niobium [904, 1451]. The latter are formed either due to the formation of a metal-metal bond, arising due to combination of a free electron pair on rhenium (V) and a vacant orbital of molybdenum (VI) atom or via insertion of molybdenum or tungsten atoms into the molecular structure characteristic of rhenium (V and VI) oxoalkox-ides. The formation of the compounds with variable composition becomes possible in the latter case. 

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