Zirconium(IV) chloride

Zirconium(IV) chloride
IUPAC name

Zirconium tetrachloride
Zirconium(IV) chloride
Identifiers
CAS number 10026-11-6 Y
ChemSpider 23202 Y
EC number 233-058-2
Jmol-3D images Image 1
Properties
Molecular formula ZrCl4
Molar mass 233.04 g/mol
Appearance white crystals
hygroscopic
Density 2.80 g/cm3
Melting point

437 °C (triple point)
Boiling point

331 °C
Solubility in water hydrolysis
Solubility soluble in alcohol, ether, concentrated HCl
Structure
Crystal structure Monoclinic, mP10
Space group P12/c1, No. 13
Thermochemistry
Std enthalpy of
formation ΔfHo298		 −980.52 kJ/mol
Standard molar
entropy So298		 181.41 J K−1 mol−1
Hazards
MSDS MSDS
EU Index Not listed
Flash point Non-flammable
LD50 1688 mg/kg (oral, rat)
Related compounds
Other anions Zirconium(IV) fluoride
Zirconium(IV) bromide
Zirconium(IV) iodide
Other cations Titanium tetrachloride
Hafnium tetrachloride
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Zirconium(IV) chloride, also known as zirconium tetrachloride, (ZrCl4) is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air.

Contents

Structure

Unlike molecular TiCl4, solid ZrCl4 adopts a polymeric structure wherein each Zr is octahedrally coordinated. This difference in structures is responsible for the striking difference in their properties: TiCl4 is distillable, but ZrCl4 is a solid with a high melting point. In the solid state, ZrCl4 adopts a tape-like linear polymeric structure—the same structure adopted by HfCl4. This polymer degrades readily upon treatment with Lewis bases, which cleave the Zr-Cl-Zr linkages.[1]

Kroll process

ZrCl4 is an intermediate in the conversion of zirconium minerals to metallic zirconium by the Kroll process. In nature, zirconium minerals invariably exist as oxides (reflected also by the tendency of all zirconium chlorides to hydrolyze). For their conversion to bulk metal, these refractory oxides are first converted to the tetrachloride, which can be distilled at high temperatures. This conversion entails treatment of the oxide with carbon as the oxide "getter" and chlorine.

ZrO2 + 2 C + 2 Cl2 → ZrCl4 + 2 CO

Chemical reactions

Hydrolysis of ZrCl4 gives the hydrated hydroxy chloride cluster called zirconyl chloride. This reaction is rapid and virtually irreversible, consistent with the high oxophilicity of zirconium(IV). For this reason, manipulations of ZrCl4 typically require air-free techniques.

ZrCl4 is the principal starting compound for the synthesis of many organometallic complexes of zirconium.[2] Because of its polymeric structure, ZrCl4 is usually converted to a molecular complex before use. It forms a 1:2 complex with tetrahydrofuran: CAS [21959-01-3], mp 175-177 °C.[3] NaC5H5 reacts with ZrCl4(THF)2 to give zirconocene dichloride, ZrCl2(C5H5)2, a versatile organozirconium complex.[4] One of the most curious properties of ZrCl4 is its high solubility in the presence of methylated benzenes, such as durene. This solubilization arises through the formation of π-complexes.[5]

ZrCl4 can be reduced with Zr metal to produce zirconium(III) chloride.

Uses

In organic synthesis zirconium tetrachloride is used as a weak Lewis acid for the Friedel-Crafts reaction, the Diels-Alder reaction and intramolecular cyclisation reactions.[6] It is also used to make water-repellent treatment of textiles and other fibrous materials.

References

  1. ^ N. N. Greenwood & A. Earnshaw, Chemistry of the Elements (2nd ed.), Butterworth-Heinemann, Oxford, 1997.
  2. ^ New Aspects of Zirconium Containing Organic Compounds. Topics in Organometallic Chemistry, 10 Edited by Ilan Marek (Technion-Israel Institute of Technology, Haifa). Springer: Berlin, Heidelberg, New York. 2005. x + 176 pp. ISBN 3-540-22221-9.
  3. ^ L. E. Manxzer, Joe Deaton, Paul Sharp, R. R. Schrock (1982). "Tetrahydrofuran Complexes of Selected Early Transition Metals". Inorganic Syntheses. Inorganic Syntheses 21: 135–140. doi:10.1002/9780470132524.ch31. ISBN 9780470132524. 
  4. ^ G. Wilkinson and J.G. Birmingham (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–4284. doi:10.1021/ja01646a008. 
  5. ^ Musso, F.; Solari, E.; Floriani, C.; Schenk, K. (1997). "Hydrocarbon Activation with Metal Halides: Zirconium Tetrachloride Catalyzing the Jacobsen Reaction and Assisting the Trimerization of Alkynes via the Formation of η6-Arene-Zirconium(IV) Complexes". Organometallics 16 (22): 4889–4895. doi:10.1021/om970438g. 
  6. ^ Bora U. (2003). "Zirconium Tetrachloride". Synlett (7): 1073–1074. doi:10.1055/s-2003-39323.