Editing Titanium (section)

=== Oxides, sulfides, and alkoxides ===
The most important oxide is TiO<sub>2</sub>, which exists in three important [[polymorphism (materials science)|polymorphs]]; anatase, brookite, and rutile. All three are white diamagnetic solids, although mineral samples can appear dark (see [[rutile]]). They adopt polymeric structures in which Ti is surrounded by six [[oxide]] ligands that link to other Ti centers.<ref name="Greenwood1997p961">{{harvnb|Greenwood|Earnshaw|1997|p=961}}</ref>

The term ''[[titanate]]s'' usually refers to titanium(IV) compounds, as represented by [[barium titanate]] (BaTiO<sub>3</sub>). With a perovskite structure, this material exhibits [[piezoelectric]] properties and is used as a transducer in the interconversion of [[sound]] and [[electricity]].<ref name="TICE6th" /> Many minerals are titanates, such as ilmenite (FeTiO<sub>3</sub>). [[Star sapphire (jewel)|Star sapphires]] and [[ruby|rubies]] get their [[asterism (gemmology)|asterism]] (star-forming shine) from the presence of titanium dioxide impurities.<ref name="Emsley2001p453" />

A variety of reduced oxides ([[suboxide]]s) of titanium are known, mainly reduced [[stoichiometry|stoichiometries]] of titanium dioxide obtained by [[atmospheric plasma spraying]]. Ti<sub>3</sub>O<sub>5</sub>, described as a Ti(IV)-Ti(III) species, is a purple semiconductor produced by [[reduction (chemistry)|reduction]] of TiO<sub>2</sub> with hydrogen at high temperatures,<ref>{{cite journal |last1=Liu |first1=Gang |last2=Huang |first2=Wan-Xia |last3=Yi |first3=Yong |title=Preparation and Optical Storage Properties of λTi<sub>3</sub>O<sub>5</sub> Powder |journal=Journal of Inorganic Materials |date=26 June 2013 |volume=28 |issue=4 |pages=425–430|doi=10.3724/SP.J.1077.2013.12309|doi-broken-date=1 November 2024 }}</ref> and is used industrially when surfaces need to be vapor-coated with titanium dioxide: it evaporates as pure TiO, whereas TiO<sub>2</sub> evaporates as a mixture of oxides and deposits coatings with variable refractive index.<ref>{{cite journal |last1=Bonardi |first1=Antonio |last2=Pühlhofer |first2=Gerd |last3=Hermanutz |first3=Stephan |last4=Santangelo |first4=Andrea |year=2014 |title=A new solution for mirror coating in {{mvar|γ}}-ray Cherenkov Astronomy |journal=Experimental Astronomy |volume=38 |issue=1–2 |pages=1–9 |doi=10.1007/s10686-014-9398-x |bibcode=2014ExA....38....1B |s2cid=119213226 |arxiv=1406.0622}}</ref> Also known is [[titanium(III) oxide|Ti<sub>2</sub>O<sub>3</sub>]], with the [[corundum]] structure, and [[titanium(II) oxide|TiO]], with the [[rock salt structure]], although often [[nonstoichiometric]].{{sfn|Greenwood|Earnshaw|1997|p=962}}

The [[alkoxide]]s of titanium(IV), prepared by treating TiCl<sub>4</sub> with [[Alcohol (chemistry)|alcohol]]s, are colorless compounds that convert to the dioxide on reaction with water. They are industrially useful for depositing solid TiO<sub>2</sub> via the [[sol-gel process]]. [[Titanium isopropoxide]] is used in the synthesis of chiral organic compounds via the [[Sharpless epoxidation]].<ref>{{cite journal |author1=Ramón, Diego J. |author2=Yus, Miguel |year=2006 |title=In the arena of enantioselective synthesis, titanium complexes wear the laurel wreath |journal=Chem. Rev. |volume=106 |issue=6 |pages=2126–2308 |doi=10.1021/cr040698p |pmid=16771446}}</ref>

Titanium forms a variety of sulfides, but only [[titanium disulfide|TiS<sub>2</sub>]] has attracted significant interest. It adopts a layered structure and was used as a cathode in the development of [[lithium batteries]]. Because Ti(IV) is a [[HSAB theory|"hard cation"]], the sulfides of titanium are unstable and tend to hydrolyze to the oxide with release of [[hydrogen sulfide]].<ref>{{cite book | last1 = McKelvy | first1 = M.J. | last2 = Glaunsinger | first2 = W.S. | year = 1995 | title = Inorganic Syntheses | chapter = Titanium Disulfide | volume = 30 | pages = 28–32 | doi = 10.1002/9780470132616.ch7 | isbn = 978-0-470-13261-6 }}</ref>