Niobium V bromide

When a sample of the niobium (V) chloride-pyridine or niobium(V) bromide-pyridine reaction mixture was dissolved in dilute acid, filtered to remove precipitated niobium oxides, and treated with concentrated sodium hydroxide solution, the same set of spectra were observed for the resulting solution as for the l-(4-pyridyl) pyridinium dihalides. The spectra before and after heating the solutions from the reaction mixtures are shown in Figure 2. Here also the peaks occurred at 432 and 365 m/x, with the 432-m, peak absent after heating. 

Samples of the niobium (V) chloride or niobium (V) bromide-pyridine reaction mixtures were hydrolyzed in concentrated hydrochloric acid. Aliquots were diluted and neutralized with sodium carbonate to a pH of approximately 8. Sodium tetraphenylborate(III) solution then was added and a precipitate of l-(4-pyridyl) pyridinium tetraphenylborate(III) was produced. The precipitate was filtered and extracted with concentrated hydrochloric acid. The ultraviolet absorption spectrum of the extract is shown in Figure 3 for comparison with the spectrum of a known sample of l-(4-pyridyl) pyridinium dichloride in dilute hydrochloric acid. 

It was thus shown that the tetrahalodi(pyridine)niobium(IV) complexes were the reduction products of the reactions of niobium(V) chloride and niobium (V) bromide with pyridine. 

These three procedures left little doubt that l-(4-pyridyl) pyridinium ion was the major oxidized product of the reaction of niobium(V) bromide and chloride with pyridine. 

Similarly, it was concluded that in the reduction reaction of niobium(V) bromide with pyridine the major products were tetrabromodi (pyridine )niobium-(IV), pyridinium bromide, and l-(4-pyridyl) pyridinium bromide. Oxidation-reduction titrations indicated approximately 90% reduction. The remaining 10% of niobium was assumed to be present as pentabromo(pyridine)niobium(V). The over-all reaction was indicated to be ... 

This apparatus has been successfully used in the preparation of niobium(V) bromide, tantalum(V) bromide, tungsten(YI) chloride, and molybdenum(V) chloride. ... 

Niobium(V) bromide (2 g.) is dissolved in anhydrous acetonitrile (10 ml.) and excess solvent removed in vacuo at room temperature to leave the dark-red solid complex (yield 100%). 

Niobium(V) bromide Niobium(V) chloride Niobium(V) fluoride Niobium(V) iodide Niobium nitride Niobium(II) oxide Niobium(IV) oxide Niobium(V) oxide Nitric acid Nitric oxide Nitrogen... 

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