Niobium oxohalides

Complex formation between Nb(OH)s and methylamine has been established582 by an n.m.r. study. Two signals are observed in the n.m.r. spectrum of an aqueous solution of methylamine containing Nb(OH)5. One of these is due to the methyl protons of the amine and the other to the rapidly exchanging protons of the OH, NH2, and H20 groups. The i.r. spectra of solutions and precipitates formed by Nb(OH)5 and methylamine or monoethanolamine have been interpreted583 in terms of Nb—N co-ordination. Niobium oxohalide complex formation with tri-n-octylamine has been studied by reverse ebullioscopy.584... 

A growing chemistry of niobium oxide clusters continues to emerge. The reduced niobates and the NbO suboxide are also built up from condensation of Me units through shared vertices, namely, Nb60i2. Although the inner halides within the [MeXi2] + core are relatively inert to substitution, Nbe and Tae oxohalides, such as [Nb6Cli2-mOm]"+ m = 1 —4) and... 

Of the halogens, only the strongly oxidizing fluorine produces a pentahalide of vanadium, and the other vanadium(V) compounds are based on the oxohalides and the pentoxide. The pentoxide also gives rise to the complicated but characteristic aqueous chemistry of the polymerized vanadates (isopolyvanadates) which anticipates the even more extensive chemistry of the poly molybdates and poly tungstates this is only incompletely mirrored by niobium and tantalum. 

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