Niobium pentaiodide
{{Chembox
| ImageFile = Nb2I10.svg
| ImageSize =
| ImageAlt =
| IUPACName =
| OtherNames = Niobium(V) iodide
|Section1={{Chembox Identifiers
| CASNo = 13779-92-5
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 6YYE4L5XPW
| PubChem = 83728
| ChemSpiderID = 75550
| EC_number = 237-422-1
| DTXSID = DTXSID1065633
| StdInChI=1S/5HI.Nb/h5*1H;/q;;;;;+5/p-5
| StdInChIKey = FWIYBTVHGYLSAZ-UHFFFAOYSA-I
| SMILES = [Nb](I)(I)(I)(I)I
}}
|Section2={{Chembox Properties
| Formula = Nb2I10
| MolarMass = 1475
| Appearance = yellow solid
| Density = 5.30 g/cm3
| MeltingPtC = 543
| MeltingPt_notes = sublimes
| BoilingPt =
| Solubility = }}
|Section7={{Chembox Hazards
| GHSPictograms = {{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
| Section9 = {{Chembox Related
| OtherCompounds = Tantalum pentaiodide
}}
}}
Niobium pentaiodide is the inorganic compound with the formula Nb2I10. Its name comes from the compound's empirical formula, NbI5.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford: Butterworth-Heinemann. {{ISBN|0-7506-3365-4}}. It is a diamagnetic, yellow solid that hydrolyses readily. The compound adopts an edge-shared bioctahedral structure, which means that two NbI5 units are joined by a pair of iodide bridges. There is no bond between the Nb centres.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. Niobium(V) chloride, niobium(V) bromide, tantalum(V) chloride, tantalum(V) bromide, and tantalum(V) iodide, all share this structural motif.
Preparation
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.{{cite book|author=G. Braurer|chapter=Niobium(V) Iodide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=1315}}
Properties
Niobium(V) iodide forms of dark, brassy, extremely moisture-sensitive needles or flakes. Its crystallises in the monoclinic crystal system with space group P21/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.{{Cite journal |last=Littke |first=W. |last2=Brauer |first2=G. |date=Oct 1963 |title=Darstellung und Kristallstruktur von Niobpentajodid |url=https://onlinelibrary.wiley.com/doi/10.1002/zaac.19633250304 |journal=Zeitschrift für anorganische und allgemeine Chemie |language=en |volume=325 |issue=3-4 |pages=122–129 |doi=10.1002/zaac.19633250304 |issn=0044-2313|url-access=subscription }} 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.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. This structure is isotypic with that of triclinic niobium(V) bromide.
References
{{niobium compounds}}
{{iodides}}