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.[3]
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.[4] 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.[3][5] 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.
^ abG. 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.
