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Niobium pentaiodide forms from the reaction of niobium with iodine:
2 Nb + 5 I2 → 2 NbI5
The method used for the preparation of tantalum(V) iodide using aluminium triiodide fails to produce pure pentaiodide.
Properties
Niobium(V) iodide forms of dark, brassy, extremely moisture-sensitive needles or flakes. Its crystallises in the monoclinic crystal system with space groupP21/c (space group no. 14), a = 1058 pm, b = 658 pm, c = 1388 pm, β = 109.14°. The crystal structure consists of zigzag chains of corner-sharing NbI6 octahedra. Since so far only twinned crystals of this phase have been obtained, and the structure determination is uncertain. If the reaction of the elements is carried out with an excess of iodine, a triclinic modification is created with the space group P1 (No. 2), a = 759.1 pm, b = 1032.2 pm, c = 697.7 pm, α = 90 .93°, β = 116.17°, γ = 109.07°, which consists of isolated molecules Nb2I10. This structure is isotypic with that of triclinic niobium(V) bromide.
References
Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford: Butterworth-Heinemann. ISBN0-7506-3365-4.
Krebs, Bernt; Sinram, Diethard "Darstellung, Struktur und Eigenschaften einer neuen Modifikation von NbI5 (Preparation, structure and properties of a new modification of NbI5" Zeitschrift fǔr Naturforschung, Teil B: Anorganische Chemie, Organische Chemie 1980, volume 35b, pp. 12-16.
^ G. Braurer (1963). "Niobium(V) Iodide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 1315.
B. Krebs, D. Sinram: Darstellung, Struktur und Eigenschaften einer neuen Modifikation von NbI5. In: Zeitschrift fuer Naturforschung, Teil B. Anorganische Chemie, Organische Chemie, 1980, 35, S. 12–16.
