Triisobutylaluminium (TiBA) is an organoaluminium compound with the formula Al(CH2CH(CH3)2)3. This colorless pyrophoric liquid is mainly used to make linear primary alcohols and α-olefins.[2]

Triisobutylaluminium

Monomeric form
Names
IUPAC name
Triisobutylaluminum
Other names
Aluminumtriisobutanide; TIBA
Identifiers
3D model (JSmol)
ECHA InfoCard 100.002.643 Edit this at Wikidata
EC Number
  • 202-906-3
UNII
UN number 3394 3051
  • InChI=1S/3C4H9.Al/c3*1-4(2)3;/h3*4H,1H2,2-3H3;
    Key: MCULRUJILOGHCJ-UHFFFAOYSA-N
  • CC(C)C[Al](CC(C)C)CC(C)C
Properties[1]
C12H27Al
Molar mass 198.330 g·mol−1
Appearance Colorless liquid
Density 0.786 g/mL at 25 °C
Melting point 4 to 6 °C (39 to 43 °F; 277 to 279 K)
Boiling point 86 °C (13 hPa)
Hazards
GHS labelling:
GHS02: FlammableGHS05: Corrosive
Danger
H250, H260, H314
P210, P222, P223, P231+P232, P260, P264, P280, P301+P330+P331, P302+P334, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P335+P334, P363, P370+P378, P402+P404, P405, P422, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure

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Triisobutylaluminium exists in equilibrium with its dimer. The equilibrium constant, KD, is 3.810 at 20 °C.[3]

2 Al(CH2CH(CH3)2)3   [Al(CH2CH(CH3)2)3]2

In the dimer, the bridging carbon-aluminium bond is elongated and exhibits evidence of restricted rotation. For the sake of simplicity, TiBA is written as the monomer in this article.

Synthesis

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Trialkylaluminium compounds are available industrially through the reactions of aluminium powder, hydrogen gas, and the desired alkenes. The synthesis of TiBA requires two steps; the first step produces diisobutylaluminium hydride (written as a monomer):

4 CH2=C(CH3)2 + 2 Al + 3 H2 → 2 HAl(CH2CH(CH3)2)2

In the second step isobutylene adds to the diisobutylaluminium to give TiBA:

CH2=C(CH3)2 + HAl(CH2CH(CH3)2)2 → Al(CH2CH(CH3)2)3

Reactions

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α-olefins are readily eliminated from β-branched trialkylaluminium compounds. Trialkylaluminium compounds are used in the industrial production of polymers. In the most common of these compounds, TIBA, a substantial level of Al – H bonds are present at equilibrium. The greater stability of unbranched trialkylaluminium compounds relative to branched trialkylaluminium compounds in TIBA forms the basis for a general synthesis of triethyl- and higher linear trialkylaluminium materials from triisobutylaluminium.

Al(CH2CH(CH3)2)3 + 3 RCH=CH2 → Al(CH2CH2R)3 + 3 CH2=C(CH3)2

Safety

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Like most organoaluminium compounds, TiBA reacts violently with water and air.[1]

References

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  1. ^ a b Sigma-Aldrich. "Triisobutylaluminum". MilliporeSigma. Merck Group. Retrieved 2021-03-15.
  2. ^ Michael J. Krause, Frank Orlandi, Alfred T. Saurage, Joseph R. Zietz Jr. "Aluminum Compounds, Organic" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_543
  3. ^ Smith, Martin B. (1970). "The Monomer-Dimer Equilibria of Liquid Ammonium Alkyls II Triisobutylaluminum". Journal of Organometallic Chemistry. 22 (2): 273–281. doi:10.1016/S0022-328X(00)86043-X.

Further reading

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  • Keisuke Suzuki, Tetsuya Nagasaws, Encyclopedia of Reagents for Organic Synthesis, Triisobutylaluminum, 2009