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Diisobutylaluminium hydride

Names
IUPAC name Diisobutylaluminum hydride
Other names DIBAH; DIBAL; DiBAlH; DIBAL-H; DIBALH
Identifiers
CAS Number	1191-15-7
3D model (JSmol)	Interactive image
ChemSpider	10430352
ECHA InfoCard	100.013.391
CompTox Dashboard (EPA)	DTXSID4041866
InChI InChI=1S/2C4H9.Al.H/c2*1-4(2)3;;/h2*4H,1H2,2-3H3;;Key: AZWXAPCAJCYGIA-UHFFFAOYSA-N InChI=1/2C4H9.Al.H/c2*1-4(2)3;;/h2*4H,1H2,2-3H3;;/rC8H19Al/c1-7(2)5-9-6-8(3)4/h7-9H,5-6H2,1-4H3Key: AZWXAPCAJCYGIA-DFAADSFOAF
SMILES CC(C)CCC(C)C
Properties
Chemical formula	C16H38Al2 (dimer)
Molar mass	142.22 (monomer)
Appearance	colorless liquid
Density	0.798 g/cm
Melting point	–18 °C
Boiling point	116–118 °C/1 mmHg
Solubility in water	hydrocarbon solvents
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	ignites in air
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Diisobutylaluminium hydride, DIBAL, DIBAL-H or DIBAH, is a reducing agent with the formula (i-Bu₂AlH)₂, where i-Bu represents isobutyl (-CH₂CH(CH₃)₂). This organoaluminium compound was investigated originally as a co-catalyst for the polymerization of alkenes.

Properties

Like most organoaluminum compounds, the compound’s structure is probably more than that suggested by its empirical formula. A variety of techniques, not including X-ray crystallography, suggest that the compound exists as a dimer and a trimer, consisting of tetrahedral aluminium centers sharing bridging hydride ligands. Hydrides are small and, for aluminium derivatives, are highly basic, thus they bridge in preference to the alkyl groups.

DIBAH can be prepared by heating triisobutylaluminium (itself a dimer) to induce beta-hydride elimination:

(i-Bu₃Al)₂ → (i-Bu₂AlH)₂ + 2 (CH₃)₂C=CH₂

Although DIBAH can be purchased commercially as a colorless liquid, it is more commonly purchased and dispensed as a solution in organic solvents such as toluene.

Use in organic synthesis

DIBAH is useful in organic synthesis for a variety of reductions, including converting esters and nitriles to aldehydes. DIBAH efficiently reduces α-β unsaturated esters to the corresponding allylic alcohol. By contrast, LiAlH₄ reduces esters and acyl chlorides to primary alcohols, and nitriles to primary amines . DIBAH reacts slowly with electron-poor compounds, and more quickly with electron-rich compounds. Thus, it is an electrophilic reducing agent whereas LiAlH₄ can be thought of as a nucleophilic reducing agent.

Safety

DIBAH, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to fires.

References

1. K. Ziegler, H. Martin and F. Krupp (1960). "Metallorganische Verbindungen, XXVII Aluminiumtrialkyle und Dialkyl-Aluminiumhydride Aus Aluminiumisobutyl-Verbindungen". Justus Liebigs Annalen der Chemie. 629 (1): 14–19. doi:10.1002/jlac.19606290103.
2. Mark F. Self, William T. Pennington and Gregory H. Robinson (1990). "Reaction of diisobutylaluminum hydride with a macrocyclic tetradentate secondary amine. Synthesis and molecular structure of ₂₂: evidence of an unusual disproportionation of (iso-Bu)2AlH". Inorganica Chimica Acta. 175 (2): 151–153. doi:10.1016/S0020-1693(00)84819-7.
3. Eisch, J. J. Organometallic Syntheses Volume 2, Academic Press: New York, 1981. ISBN 0-12-234950-4.
4. Galatsis, P. “Diisobutylaluminum Hydride” in Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons: New York, 2001. doi:10.1002/047084289X.rd245

External links

• Example use
• Overview of reduction
• DIBAL reduction review

• Organoaluminium compounds
• Metal hydrides
• Reducing agents