Niobium oxychloride

Niobium oxychloride

Names
IUPAC name Niobium (V) Oxychloride
Other names Niobium oxytrichloride
Identifiers
CAS Number	13597-20-1 Y
Properties
Chemical formula	Cl3NbO
Molar mass	215.26 g·mol−1
Appearance	white crystals
Melting point	sublimes above 200 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Niobium oxychloride is the inorganic compound with the formula NbOCl₃. It is a white, crystalline, diamagnetic solid. It is often found as an impurity in samples of niobium pentachloride, a common reagent in niobium chemistry.

Structure

In the solid state the coordination sphere for niobium is a distorted octahedron. The Nb-O bonds and Nb-Cl bonds are unequal. This structure can be described as planar Nb₂Cl₆ core connected by O-Nb-O bridges. In this way, the compound is best described as a polymer, consisting of a double stranded chain.^[1][2]

In the gas phase above 320 °C the Raman spectrum is consistent with a pyramidal monomer containing a niobium oxygen double bond.^[3]

Upon being evaporated NbOCl₃ is a tetrahedral molecule (Nb=O double bond is an artifact).

Synthesis

Niobium oxychloride is prepared by treating the pentachloride with oxygen:^[4]

NbCl₅ + 1/2 O₂ → NbOCl₃ + Cl₂

This reaction is conducted at about 200 °C. NbOCl₃ also forms as a major side-product in the reaction of niobium pentoxide with various chlorinating agents such as carbon tetrachloride and thionyl chloride.^[4][5]

2 Nb₂O₅ + 6 CCl₄ → 4 NbOCl₃ + 6 COCl₂

References

1. ↑ Ströbele, Markus; Meyer, Hans-Jürgen (2002). "Neubestimmung der Kristallstruktur von NbOCl₃". Zeitschrift für anorganische und allgemeine Chemie 628: 488–491. doi:10.1002/1521-3749(200202)628:2<488::AID-ZAAC488>3.0.CO;2-B. 
2. ↑ Beck, Johannes; Bordinhão, Jairo (2005). "Polar [NbOCl₃]_2n and [NbOX₄⁻]_n (X = Cl, Br) Chains in the Structures of NbOCl₃ and the Thallium-Halogenooxoniobates Tl[NbOCl₄] and Tl[NbOBr₄] - Synthesis, Crystal Structures and Optical Second Harmonic Generation". Zeitschrift für anorganische und allgemeine Chemie 631 (6–7): 1261–1266. doi:10.1002/zaac.200500041. 
3. ↑ Greenwood, N.N. (January 1, 1970). "Chapter 5: Vibrational Spectra". Spectroscopic Properties of Inorganic and Organometallic Compounds. Royal Society of Chemistry. p. 196. ISBN 9780851860237. 
4. 1 2 "Niobium Oxytrichloride" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 2. pp. 1307.
5. ↑ Jena, P. K.; Brocchi, E. A.; Garcia, R. I. (1997). "Kinetics of chlorination of niobium pentoxide by carbon tetrachloride". Metallurgical and Materials Transactions B 28: 39–45. doi:10.1007/s11663-997-0125-0. .