Titanium tetrabromide

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Titanium tetrabromide
Titanium tetrabromide
Ball-and-stick model of the titanium tetrabromide molecule
Identifiers
CAS number 7789-68-6 YesY
PubChem 123263
EC number 232-185-0
Jmol-3D images Image 1
Properties
Molecular formula TiBr4
Molar mass 367.483 g/mol
Appearance brown crystals
hygroscopic
Density 3.25 g/cm3
Melting point 39 °C (102 °F; 312 K)
Boiling point 230 °C (446 °F; 503 K)
Solubility in water decomposition
Solubility in other solvents chlorocarbons, benzene
Structure
Crystal structure cubic, Pa3, Z = 8
Coordination
geometry
Tetrahedral
Dipole moment 0 D
Hazards
R-phrases 14-34
S-phrases 26-36/37/39-45
Main hazards corrosive
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions TiCl4
TiI4
Other cations VCl4
Related compounds TiCl3
VBr3
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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.[1]

Preparation and structure[edit]

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[edit]

Titanium tetrabromide forms adducts such as TiBr4(THF)2 and [TiBr5]-.[2] 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.[3]

TiBr4 has been used as a Lewis-acid catalyst in organic synthesis.[4]

The tetrabromide and tetrachlorides of titanium react to give a statistical mixture of the mixed tetrahalides, TiBr4-xClx (x = 0-4). The mechanism of this redistribution reaction is uncertain. One proposed pathway invokes the intermediacy of dimers.[5]

Safety[edit]

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

References[edit]

  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ Colin S. Creaser and J. Alan Creighton (1975). "Pentachloro- and pentabromo-titanate(IV) ions". J. Chem. Soc., Dalton Trans. (14): 1402–1405. doi:10.1039/DT9750001402. 
  3. ^ Hensen, K.; Lemke, A.; Bolte, M. (2000). "Tetrabromo(2-methylpyridine-N)-titanate(IV)". Acta Crystallographica C56 (12): e565 – e566. doi:10.1107/S0108270100015407. 
  4. ^ B. Patterson, S. Marumoto and S. D. Rychnovsky (2003). "Titanium(IV)-Promoted Mukaiyama Aldol-Prins Cyclizations". Org. Lett. 5 (17): 3163–3166. doi:10.1021/ol035303n. PMID 12917007. 
  5. ^ S. P. Webb and M. S. Gordon (1999). "Intermolecular Self-Interactions of the Titanium Tetrahalides TiX4 (X = F, Cl, Br)". J. Am. Chem. Soc. 121 (11): 2552–2560. doi:10.1021/ja983339i.