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Halides

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds. The pentahalides (NbX) feature octahedral Nb centres. Niobium pentafluoride (NbF) is a white solid with a melting point of 79.0 °C and niobium pentachloride (NbCl) is yellow (see image at right) with a melting point of 203.4 °C. Both are hydrolyzed to give oxides and oxyhalides, such as NbOCl. The pentachloride is a versatile reagent used to generate the organometallic compounds, such as niobocene dichloride ((C H) NbCl). The tetrahalides (NbX) are dark-coloured polymers with Nb-Nb bonds; for example, the black hygroscopic niobium tetrafluoride (NbF) and brown niobium tetrachloride (NbCl).

Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is, an intermediate in the separation of Nb and Ta from the ores. This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral:

As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being.