Triisobutylaluminium

Triisobutylaluminium

Monomeric form
Names
IUPAC name Triisobutylaluminum
Other names Aluminumtriisobutanide; TIBA
Identifiers
CAS Number	100-99-2
3D model (JSmol)	Interactive image
ECHA InfoCard	100.002.643
CompTox Dashboard (EPA)	DTXSID0026670
SMILES CC(C)C[Al](CC(C)C)CC(C)C
Properties
Chemical formula	C12H27Al
Molar mass	198.330 g·mol−1
Appearance	Colorless liquid
Density	0.786 g/mL at 25°C
Boiling point	86 °C (187 °F; 359 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Triisobutylaluminium (TiBA) is is a colorless solution and is mainly used to make linear primary alcohols and αあるふぁ-olefins.

Structure

Triisobutylaluminium was thought to be monomeric, however, it was discovered to exist in equilibrium with its dimer form. To allow for the dimer to form, there is an appreciable increase in the length of the bonds between Al and the bridging alkyl ligand. There is also evidence of restricted rotation of the bridging isobutyl groups. The equilibrium constant, K_D, is 3.810 at 20 °C.

Synthesis

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 by this route.

6 iBu₃ + 2 Al + 3 H₂ → 6 iBu₂AlH

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

6 iBu₂AlH + 6 (C₄H₈) → 6 iBu₃Al

Reactions

αあるふぁ-olefins are readily eliminated from βべーた-branched trialkylaluminium compounds. Trialkylaluminium compounds are used to industrially produce 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.

(iC₄H₉)₃Al + 3RCH=CH₂ →(RCH₂CH₃)3Al + 3iC₄H₈

Like most organoaluminium compounds, TiBA reacts violently with water and must be handled with care.

References

1. Michael J. Krause, Ullmans Encyclopedia of Industrial Chemistry, Aluminum Compounds, Organic, 2005
2. Martin B. Smith, Journal of Organometallic Chemistry, The Monomer-Dimer Equilibria of Liquid Ammonium Alkyls II Triisobutylaluminum, 1969
3. Keisuke Suzuki, Tetsuya Nagasaws, Encyclopedia of Reagents for Organic Synthesis, Triisobutylaluminum, 2009