tert-Butylamine borane
[CAS# 7337-45-3]

Identification

• Classification: Chemical reagent >> Organic reagent >> Borane
• Name: tert-Butylamine borane
• Molecular Formula: C₄H₁₁N.BH₃
• Molecular Weight: 86.97
• CAS Registry Number: 7337-45-3
• EC Number: 230-851-5
• SMILES: [B].CC(C)(C)N

Properties

• Melting point: 96-101 °C (dec.)

Safety Data

• Hazard Symbols: GHS06;GHS09 Danger
• Risk Statements: H301+H311,H315,H319,H411
• Safety Statements: P264-P273-P280-P301+P310-P302+P352+P312-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	3	H301
Skin irritation	Skin Irrit.	2	H315
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	3	H311
Specific target organ toxicity - single exposure	STOT SE	3	H335
Flammable solids	Flam. Sol.	2	H228
Flammable solids	Flam. Sol.	1	H228

• Transport Information: UN 2811

Discovery and Applications

tert-Butylamine borane is an organoboron compound consisting of a tert-butylamine moiety coordinated to a borane (BH3) group, forming a stable adduct. Its molecular formula is C4H13NB. The compound is typically a colorless to pale yellow solid or crystalline material that is soluble in polar organic solvents such as tetrahydrofuran, ethanol, or dichloromethane. The adduct formation between the tertiary amine and borane stabilizes the reactive BH3 unit, allowing safer handling compared to free borane.

The discovery and development of amine-borane adducts, including tert-butylamine borane, stem from the need for stable, easily handled sources of borane for use in organic synthesis and reduction chemistry. Borane itself is highly reactive and pyrophoric, but coordination to a Lewis base such as tert-butylamine produces a solid or liquid complex that retains the reducing properties of BH3 while being much safer to store and handle. These adducts have been extensively studied since the mid-20th century for applications in hydroboration, reduction, and hydrogen storage.

Synthesis of tert-butylamine borane is typically performed by direct reaction of tert-butylamine with borane in an inert solvent under controlled conditions. A common method involves bubbling diborane (B2H6) or using a commercially available borane–tetrahydrofuran solution into a cooled solution of tert-butylamine. The reaction proceeds spontaneously with the formation of a stable dative bond between the nitrogen lone pair and the boron atom. The product can be isolated by crystallization or distillation under reduced pressure to remove unreacted reagents and solvent.

Chemically, tert-butylamine borane functions as a mild and selective reducing agent due to the BH3 moiety. The boron atom can transfer hydride ions to electrophilic centers such as carbonyl compounds, imines, and certain unsaturated systems, resulting in the reduction of ketones, aldehydes, and imines to the corresponding alcohols or amines. The sterically bulky tert-butyl group provides some protection to the boron, modulating its reactivity compared to less hindered amine-borane adducts. The compound is stable under dry, inert conditions but can release hydrogen or decompose upon exposure to moisture, acids, or high temperatures.

In practical applications, tert-butylamine borane is employed in organic synthesis as a selective reducing agent for the reduction of aldehydes, ketones, and imines under mild conditions. Its stability and ease of handling make it suitable for laboratory-scale reactions, particularly when controlled delivery of borane is required. In addition, tert-butylamine borane and related amine-borane adducts are studied as potential hydrogen storage materials due to their high hydrogen content and ability to release hydrogen upon thermal or catalytic activation.

Physically, the compound is generally stable when stored as a solid in airtight containers under an inert atmosphere, away from moisture and heat. Handling precautions include gloves, eye protection, and proper ventilation, as exposure to water or acids can release flammable hydrogen gas. It is also sensitive to strong oxidizers and should be stored away from reactive chemicals.

Overall, tert-butylamine borane is a useful organoboron compound that combines the reducing power of BH3 with the stability imparted by a bulky amine. Its controlled reactivity, ease of handling, and versatility in reduction reactions make it a valuable reagent in synthetic organic chemistry, with potential applications in hydrogen storage and related fields.

References

2016. Novel stereoselective bufadienolides reveal new insights into the requirements for Na(+), K(+)-ATPase inhibition by cardiotonic steroids. Scientific Reports.
DOI: 10.1038/srep29155