Titanium tetrabromide

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]

Titanium tetrabromide
Names
IUPAC name
Titanium(IV) bromide
Other names
Titanium tetrabromide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.029.259
EC Number
  • 232-185-0
UNII
Properties
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)
hydrolyses
Solubility in other solvents chlorocarbons, benzene
Structure
cubic, Pa3, Z = 8
Tetrahedral
0 D
Hazards
Main hazards corrosive
R-phrases (outdated) 14-34
S-phrases (outdated) 26-36/37/39-45
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
0
3
1
Flash point Non-flammable
Related compounds
Other anions
 Titanium(IV) chloride
Titanium(IV) fluoride
Titanium(IV) iodide
Related compounds
 Titanium(III) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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

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

TiBr4 hydrolyzes rapidly, potentially dangerously, to release hydrogen bromide, otherwise known as hydrobromic acid.

References
  1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. Colin S. Creaser & 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 & 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 & 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.
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