:Zirconium(IV) chloride

Unlike molecular TiCl₄, solid ZrCl₄ adopts a polymeric structure wherein each Zr is octahedrally coordinated. This difference in structures is responsible for the disparity in their properties: {{chem|TiCl|4}} is distillable, but {{chem|ZrCl|4}} is a solid. 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.N. N. Greenwood & A. Earnshaw, Chemistry of the Elements (2nd ed.), Butterworth-Heinemann, Oxford, 1997.

This conversion entails treatment of zirconium oxide with carbon in the presence of chlorine at high temperature:

:ZrO₂ + 2 C + 2 Cl₂ → ZrCl₄ + 2 CO

A laboratory scale process uses carbon tetrachloride in place of carbon and chlorine:{{cite book |first1=W. S. |last1=Hummers |first2=S. Y. |last2=Tyree |first3=S. |last3=Yolles |chapter=Zirconium and Hafnium Tetrachlorides |title=Inorganic Syntheses |year=1953 |volume=IV |page=121 |doi=10.1002/9780470132357.ch41 |publisher=McGraw-Hill Book Company, Inc.|isbn=978-0-470-13235-7 }}

:ZrO₂ + 2 CCl₄ → ZrCl₄ + 2 COCl₂

ZrCl₄ is an intermediate in the conversion of zirconium minerals to metallic zirconium by the Kroll process. In nature, zirconium minerals usually 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.

ZrCl₄ is the most common precursor for chemical vapor deposition of zirconium dioxide and zirconium diboride.{{cite journal |first=E.|last=Randich |title=Chemical vapor deposited borides of the form (Ti,Zr)B₂ and (Ta,Ti)B₂ |journal=Thin Solid Films |volume=63 |issue=2 |date=1 November 1979 |pages=309–313 |doi=10.1016/0040-6090(79)90034-8|bibcode = 1979TSF....63..309R }}

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.{{cite journal | author= Bora U. | title= Zirconium Tetrachloride | journal= Synlett | year= 2003 | pages= 1073–1074 |doi=10.1055/s-2003-39323 | issue= 7| doi-access= free }} It is also used to make water-repellent treatment of textiles and other fibrous materials.

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.{{cite book |title=New Aspects of Zirconium Containing Organic Compounds |series=Topics in Organometallic Chemistry |volume=10 |editor=Ilan Marek |publisher=Springer: Berlin, Heidelberg, New York |year=2005 |isbn=978-3-540-22221-7 |doi=10.1007/b80198 |issn=1436-6002}} 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.{{cite book |author1=L. E. Manzer |author2=Joe Deaton |chapter=31. Tetragtdrfuran Complexes of Selected Early Transition Metals | title = Inorganic Syntheses | year = 1982 | volume = 21 | pages = 135–140 | doi = 10.1002/9780470132524.ch31 | isbn = 978-0-470-13252-4}} Sodium cyclopentadienide (NaC₅H₅) reacts with ZrCl₄(THF)₂ to give zirconocene dichloride, ZrCl₂(C₅H₅)₂, a versatile organozirconium complex.{{cite journal | author-link=Geoffrey Wilkinson |first1=G. |last1=Wilkinson |first2=J. G. |last2=Birmingham | year = 1954 | title = Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta | journal = J. Am. Chem. Soc. | volume = 76 | issue = 17 | pages = 4281–4284 | doi = 10.1021/ja01646a008}} 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.{{cite journal |author1=Musso, F. |author2=Solari, E. |author3=Floriani, C. |author4=Schenk, K. | title = 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 | journal = Organometallics | year = 1997 | volume = 16 | pages = 4889–4895 | doi = 10.1021/om970438g | issue = 22}}

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 torrs and temperature in kelvins. 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 torrs.{{cite journal |first1=A. A. |last1=Palko |first2=A. D. |last2=Ryon |first3=D. W. |last3=Kuhn |title=The Vapor Pressures of Zirconium Tetrachloride and Hafnium Tetrachloride |journal=J. Phys. Chem. |date=March 1958 |volume=62 |issue=3 |pages=319–322 |doi=10.1021/j150561a017|hdl=2027/mdp.39015086513051 |hdl-access=free}}

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{{Zirconium compounds}}

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Category:Zirconium(IV) compounds

Category:Chlorides

Category:Metal halides

Category:Coordination complexes