Zirconium(IV) chloride

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Zirconium(IV) chloride
Zirconium-tetrachloride-3D-balls-A.png
Zirconium-tetrachloride-3D-balls-B.png
Identifiers
CAS number 10026-11-6 YesY
ChemSpider 23202 YesY
EC number 233-058-2
ChEBI CHEBI:77566 N
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 (sublimes)
Solubility in water hydrolysis
Solubility soluble in alcohol, ether, concentrated HCl
Structure
Crystal structure Monoclinic, mP10
Space group P12/c1, No. 13
Thermochemistry
Specific
heat capacity
C
125.38 J K−1 mol−1
Std molar
entropy
So298
181.41 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
−980.52 kJ/mol
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
Related compounds Zirconium(II) chloride, Zirconium(III) chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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.

Structure[edit]

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: TiCl
4
is distillable, but ZrCl
4
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]

Synthesis[edit]

This conversion entails treatment of the oxide with carbon as the oxide "getter" and chlorine.

ZrO2 + 2 C + 2 Cl2 → ZrCl4 + 2 CO

A laboratory scale process uses carbon tetrachloride in place of carbon and chlorine:[2]

ZrO2 + 2 CCl4 → ZrCl4 + 2 COCl2

Applications[edit]

Precursor to Zr metal[edit]

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

Other uses[edit]

ZrCl4 is the most common precursor for chemical vapor deposition of zirconium dioxide and zirconium diboride.[3]

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.[4] It is also used to make water-repellent treatment of textiles and other fibrous materials.

Properties and reactions[edit]

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.[5] 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.[6] NaC5H5 reacts with ZrCl4(THF)2 to give zirconocene dichloride, ZrCl2(C5H5)2, a versatile organozirconium complex.[7] 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.[8]

The log (base 10) of the vapor pressure of zirconium tetrachloride (from 480 to 689 K) is given by the equation: log10(P) =−5400/T +11.766; where the pressure is measured in torr and temperature in kelvin. The log (base 10) of the vapor pressure of solid zirconium tetrachloride (from 710 to 741 K) is given by the equation log10(P) =−3427/T +9.088. The pressure at the melting point is 14,500 torr.[9]

References[edit]

  1. ^ N. N. Greenwood & A. Earnshaw, Chemistry of the Elements (2nd ed.), Butterworth-Heinemann, Oxford, 1997.
  2. ^ Hummers, W. S.; Tyree, S. Y.; Yolles, S. (1953). "Zirconium and Hafnium Tetrachlorides". Inorganic Syntheses IV. McGraw-Hill Book Company, Inc. p. 121. doi:10.1002/9780470132357.ch41. 
  3. ^ Randich, E. (1 November 1979). "Chemical vapor deposited borides of the form (Ti,Zr)B2 and (Ta,Ti)B2". Thin Solid Films 63 (2): 309–313. doi:10.1016/0040-6090(79)90034-8. 
  4. ^ Bora U. (2003). "Zirconium Tetrachloride". Synlett (7): 1073–1074. doi:10.1055/s-2003-39323. 
  5. ^ Ilan Marek, ed. (2005). New Aspects of Zirconium Containing Organic Compounds. Topics in Organometallic Chemistry 10. Springer: Berlin, Heidelberg, New York. doi:10.1007/b80198. ISBN 978-3-540-22221-7. ISSN 1436-6002. 
  6. ^ L. E. Manzer, Joe Deaton (1982). "Tetrahydrofuran Complexes of Selected Early Transition Metals". Inorganic Syntheses. Inorganic Syntheses 21: 135–140. doi:10.1002/9780470132524.ch31. ISBN 978-0-470-13252-4. 
  7. ^ Wilkinson, G.; Birmingham, J. G. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–4284. doi:10.1021/ja01646a008. 
  8. ^ 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. 
  9. ^ Palko, A. A.; Ryon, A. D.; Kuhn, D. W. (March 1958). "The Vapor Pressures of Zirconium Tetrachloride and Hafnium Tetrachloride". J. Phys. Chem. 62: 319–322. doi:10.1021/j150561a017.