Titanium tetrabromide

Chembox new
Name = Titanium tetrabromide
ImageFile = TiBr4.png ImageName = Titanium tetrabromide
ImageFile1 = Titanium-tetrabromide-3D-balls.png ImageName1 = Ball-and-stick model of the titanium tetrabromide molecule
IUPACName = Titanium tetrabromide
OtherNames = Titanium(IV) bromide
Section1 = Chembox Identifiers
CASNo = 7789-68-6
RTECS =
Section2 = Chembox Properties
Formula = TiBr₄
MolarMass = 367.48 g/mol
Appearance = brown crystals, hygroscopic
Density = 3.25 g/mL at 25 °C, solid
Solubility = decomposition
Solvent = other solvents
SolubleOther = chlorocarbons, benzene
MeltingPt = 38-40 °C
BoilingPt = 230 °C
Section3 = Chembox Structure
Coordination = Tetrahedral
Dipole = 0 D
Section7 = Chembox Hazards
ExternalMSDS =
MainHazards = corrosive
FlashPt = nonflammable
RPhrases = 14-34
SPhrases = 26-36/37/39-45
Section8 = Chembox Related
OtherAnions = TiCl₄
TiI₄
OtherCations = VCl₄
OtherCpds = TiCl₃
VBr₃

Titanium tetrabromide is the chemical compound with the formula TiBr₄. It is the most volatile transition metal bromide. The properties of TiBr₄ are an average of TiCl₄ and TiI₄. Some key properties of these four-coordinated Ti(IV) species are their high Lewis acidity and their high solubility in nonpolar organic solvents. TiBr₄ is diamagnetic, reflecting the d⁰ configuration of the metal centre. [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.]

Preparation and structure

This four-coordinated complex adopts a tetrahedral geometry. It can be prepared via several methods: (i) from the elements, (ii) via the reaction of TiO₂ with carbon and bromine (see Kroll process), and (iii) by treatment of TiCl₄ with HBr.

Reactions

TiBr₄ forms adducts such as TiBr₄(THF)₂ and [TiBr₅] ^-. [cite journal | journal = J. Chem. Soc., Dalton Trans. | year = 1975 | pages = 1402–1405 | doi = 10.1039/DT9750001402 | title =Pentachloro- and pentabromo-titanate(IV) ions | author = Colin S. Creaser and J. Alan Creighton] With bulky donor ligands, such as 2-methylpyridine (2-Mepy), five-coordinated adducts form. TiBr₄(2-MePy) is trigonal bipyramidal with the pyridine in the equatorial plane. [cite journal | author = Hensen, K.; Lemke, A.; Bolte, M. | title = Tetrabromo(2-methylpyridine-N)-titanate(IV) | journal = Acta Crystallographica | year = 2000 | volume = C56 | pages = e565 - e566 | doi = 10.1107/S0108270100015407]

TiBr₄ has been used as a Lewis-acid catalyst in organic synthesis. [cite journal | author = B. Patterson, S. Marumoto and S. D. Rychnovsky | title = Titanium(IV)-Promoted Mukaiyama Aldol-Prins Cyclizations | year = 2003 | journal = Org. Lett. | volume = 5 | issue = 17 | pages = 3163–3166 | doi = 10.1021/ol035303n]

TiBr₄ reacts rapidly with TiCl₄ to give a statistical mixture of the tetrahalides, TiBr_4-xCl_x (x = 0-4). The mechanism of this exchange is a matter of some dispute; a reasonable pathway involves the intermediacy of dimers. [cite journal | author = S. P. Webb and M. S. Gordon | title = Intermolecular Self-Interactions of the Titanium Tetrahalides TiX4 (X = F, Cl, Br) | year = 1999 | journal = J. Am. Chem. Soc. | volume = 121 | issue = 11 | pages = 2552–2560 | doi = 10.1021/ja983339i]

afety

TiBr₄ hydrolyzes rapidly, potentially dangerously, to release hydrogen bromide.

References