Zirconium compounds are compounds formed by the element zirconium (Zr). Like other transition metals, zirconium forms a wide range of inorganic compounds and coordination complexes.[1] In general, these compounds are colourless diamagnetic solids wherein zirconium has the oxidation state +4. Far fewer Zr(III) compounds are known, and Zr(II) is very rare.
Oxides, nitrides, and carbides
editThe most common oxide is zirconium dioxide, ZrO2, also known as zirconia. This clear to white-coloured solid has exceptional fracture toughness (for a ceramic) and chemical resistance, especially in its cubic form.[2] These properties make zirconia useful as a thermal barrier coating,[3] although it is also a common diamond substitute.[2] Zirconium monoxide, ZrO, is also known and S-type stars are recognised by detection of its emission lines.[4]
Zirconium tungstate has the unusual property of shrinking in all dimensions when heated, whereas most other substances expand when heated.[5] Zirconyl chloride is a rare water-soluble zirconium complex with the relatively complicated formula [Zr4(OH)12(H2O)16]Cl8.
Zirconium carbide and zirconium nitride are refractory solids. The carbide is used for drilling tools and cutting edges. Zirconium hydride phases are also known.
Lead zirconate titanate (PZT) is the most commonly used piezoelectric material, with applications such as ultrasonic transducers, hydrophones, common rail injectors, piezoelectric transformers and micro-actuators.
Halides and pseudohalides
editAll four common halides are known, ZrF4, ZrCl4, ZrBr4, and ZrI4. All have polymeric structures and are far less volatile than the corresponding monomeric titanium tetrahalides. All tend to hydrolyse to give the so-called oxyhalides and dioxides.
The corresponding tetraalkoxides are also known. Unlike the halides, the alkoxides dissolve in nonpolar solvents. Dihydrogen hexafluorozirconate is used in the metal finishing industry as an etching agent to promote paint adhesion.[6]
Organic derivatives
edit
Organozirconium chemistry is key to Ziegler–Natta catalysts, used to produce polypropylene. This application exploits the ability of zirconium to reversibly form bonds to carbon. Zirconocene dibromide ((C5H5)2ZrBr2), reported in 1952 by Birmingham and Wilkinson, was the first organozirconium compound.[7] Schwartz's reagent, prepared in 1970 by P. C. Wailes and H. Weigold,[8] is a metallocene used in organic synthesis for transformations of alkenes and alkynes.[9]
Most complexes of Zr(II) are derivatives of zirconocene, one example being (C5Me5)2Zr(CO)2.
See also
editReferences
edit- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ a b "Zirconia". AZoM.com. 2008. Retrieved 2008-03-17.
- ^ Gauthier, V.; Dettenwanger, F.; Schütze, M. (2002-04-10). "Oxidation behavior of γ-TiAl coated with zirconia thermal barriers". Intermetallics. 10 (7): 667–674. doi:10.1016/S0966-9795(02)00036-5.
- ^ Keenan, P. C. (1954). "Classification of the S-Type Stars". Astrophysical Journal. 120: 484–505. Bibcode:1954ApJ...120..484K. doi:10.1086/145937.
- ^ Cite error: The named reference
CRC2008was invoked but never defined (see the help page). - ^ MSDS sheet for Duratec 400, DuBois Chemicals, Inc.
- ^ Wilkinson, G.; Birmingham, J. M. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". Journal of the American Chemical Society. 76 (17): 4281–4284. doi:10.1021/ja01646a008.; Rouhi, A. Maureen (2004-04-19). "Organozirconium Chemistry Arrives". Chemical & Engineering News. 82 (16): 36–39. doi:10.1021/cen-v082n016.p036. ISSN 0009-2347. Retrieved 2008-03-17.
- ^ Wailes, P. C. & Weigold, H. (1970). "Hydrido complexes of zirconium I. Preparation". Journal of Organometallic Chemistry. 24 (2): 405–411. doi:10.1016/S0022-328X(00)80281-8.
- ^ Hart, D. W. & Schwartz, J. (1974). "Hydrozirconation. Organic Synthesis via Organozirconium Intermediates. Synthesis and Rearrangement of Alkylzirconium(IV) Complexes and Their Reaction with Electrophiles". Journal of the American Chemical Society. 96 (26): 8115–8116. doi:10.1021/ja00833a048.