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Diborane Basic information

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Diborane Chemical Properties

Melting point:
Boiling point:
Flash point:
colorless gas
Repulsive odor detectable at 1.8 to 3.5 ppm
Water Solubility 
Exposure limits
TLV-TWA 0.11 mg/m3 (0.1 ppm) (ACGIH and OSHA); IDLH 40 ppm (NIOSH).
NIST Chemistry Reference
EPA Substance Registry System
Diborane (19287-45-7)

Safety Information

Hazard Codes 
Risk Statements 
Safety Statements 
UN 1911/1953
Autoignition Temperature
38 to 52 °C
Hazardous Substances Data
19287-45-7(Hazardous Substances Data)
LC50 inhal (rat) 50 ppm (4 h)
PEL (OSHA) 0.1 ppm
TLV-TWA (ACGIH) 0.1 ppm

Diborane Usage And Synthesis

Chemical Properties

Diborane is a compressed, colorless, and flam- mable gas. It has a nauseating, sickly sweet odor.


Diborane is used as a rocket propellant, in thevulcanization of rubber, as a polymerizationcatalyst, as a reducing agent, in the synthesisof trialkyl boranes, and as a doping agent(Merck 1996).


As catalyst for olefin polymerization; as rubber vulcanizer; as reducing agent; as flame-speed accelerator; in rocket propellants; in intermediate in preparation of the boron hydrides; in conversion of olefins to trialkylboranes and primary alcohols; as a doping gas.

Air & Water Reactions

Highly flammable. Ignites spontaneously in moist air (forms hydrogen and boric acid), [Haz. Chem. Data (1966)]. Oxygen and Diborane form spontaneously explosive mixtures, [J. Amer. Chem. Soc. 76, 1997(1954)].

Reactivity Profile

Diborane is a colorless, air and moisture-sensitive gas, highly toxic. Diborane ignites in air. Diborane is very explosive when exposed to heat or flame, on contact with moisture Diborane produces hydrogen gas. Explosive reaction with benzene vapor, chlorine, nitric acid and tetravinyllead [Bretherick, 5th ed., 1995, p. 77]. Explosive reaction with dimethyl sulfoxide [Shriver, 1969, p. 209], violent reaction with halocarbon liquids used as fire extinguishants (e.g., carbon tetrachloride). Reaction with Al or Li produces complex hydrides that may ignite spontaneously in air [Haz. Chem. Data, 1975, p. 114].

Health Hazard

Boranes are highly toxic by inhalation, skin absorption or ingestion. They may produce acute or chronic poisoning. Diborane is an irritant to the lungs and kidneys. The primary effect of Diborane poisoning is lung congestion caused by local tissue irritation produced by the exothermic reaction of hydrolysis.

Health Hazard

Inhalation of diborane gas results in irritation of the respiratory tract and may result in headache, cough, nausea, difficulty in breathing, chills, fever, and weakness. The odor of diborane cannot be detected below the permissible exposure limit, so this substance is considered to have poor warning properties. Overexposure to diborane can cause damage to the central nervous system, liver, and kidneys. Death can result from pulmonary edema (fluid in the lungs) and/or from lack of oxygen. Exposure to diborane gas has not been found to have significant effects on the skin and mucous membranes, but high concentrations can cause eye irritation, and contact with the liquid can cause burns. Chronic exposure to low concentrations of diborane may cause headache, lightheadedness, fatigue, weakness in the muscles, and tremors. Repeated exposure may produce chronic respiratory distress, particularly in susceptible individuals. An existing dermatitis may also be worsened by repeated exposure to the liquid. Diborane has not been shown to have carcinogenic or reproductive or developmental effects in humans.

Health Hazard

Animal studies indicate that exposure todiborane results in irritation and possibleinfection in respiratory passage. In additionto the acute poisoning of the lungs, this gasmay cause intoxication of the central nervoussystem. A 4-hour exposure to 60 ppm maybe lethal to mice, resulting in death frompulmonary edema.

Fire Hazard

Diborane is a flammable gas that ignites spontaneously in moist air at room temperature and forms explosive mixtures with air from 0.8% up to 88% by volume. Diborane reacts with halogenated hydrocarbons, and fire extinguishing agents such as Halon or carbon tetrachloride are therefore not recommended. Carbon dioxide extinguishers should be used to fight diborane fires. Fires involving diborane sometimes release toxic gases such as boron oxide smoke.

Fire Hazard

Diborane will ignite spontaneously in moist air at room temperature. Also, Diborane reacts violently with vaporizing liquid-type extinguishing agents. Diborane hydrolyzes in water to hydrogen and boric acid. Incompatible with air, halogenated compounds, aluminum, lithium, active metals, oxidized surfaces, chlorine, fuming nitric acid, nitrogen trifluoride, oxygen, and phosphorus trifluoride. Avoid moist air, electrical sparks, open flames or any other heat source. Hazardous polymerization may occur.

Flammability and Explosibility

Diborane is a flammable gas that ignites spontaneously in moist air at room temperature and forms explosive mixtures with air from 0.8% up to 88% by volume. Diborane reacts with halogenated hydrocarbons, and fire extinguishing agents such as Halon or carbon tetrachloride are therefore not recommended. Carbon dioxide extinguishers should be used to fight diborane fires. Fires involving diborane sometimes release toxic gases such as boron oxide smoke.

Safety Profile

Poison by inhalation. An irritant to skin, eyes, and mucous membranes comparable to chlorine, fluorine, arsine, and phosgene. The liquid causes local inflammation, blisters, redness, and swelling. Injuries to central nervous system, liver, and hdneys have also been produced in experimental animals. Sirmlar observations have been reported in humans, resulting at times in a reaction resembling metal fume fever. Human exposure to pentaborane has produced signs of severe central nervous system irritation such as drowsiness, dlzziness, visual disturbances, muscle twitching, and in severe cases, painful muscle spasm. Dangerously flammable when exposed to heat or flame or by chemical reaction. On contact with moisture, hydrogen is usually evolved. Highly explosive when exposed to heat or flame. Explosive reaction with air, tetravinyllead, O2 above 165℃, octanol oxime + sodium hydroxide, benzene vapor, HNO3Cl2. Violent reaction with halocarbon liquids. Other boron hydrides evolve H2 upon contact with moisture or can propagate a flame rapidly enough to cause an explosion. Heat can cause these materials to decompose violently or at least to evolve H2. They also react with water or steam to evolve hydrogen. Reaction with Al or Li forms complex hydrides that may ignite spontaneously in air. Powerful oxidlzing agents, such as chlorine gas, etc., can react violently with boron hydrides. Pentaborane (stable) is spontaneously flammable in air. See also BORANES and HYDRIDES.

Potential Exposure

Diborane is used as the source of boron in the semiconductor industry; as a catalyst for olefin polymerization; a rubber vulcanizer; a reducing agent; a flame-speed accelerator; a chemical intermediate for other boron hydrides; as a doping agent; in rocket propel- lants, and in the conversion of olefins to trialkyl boranes and primary alcohols.


diborane should be used only in a fume hood free of ignition sources and should be stored in a cold, dry, wellventilated area separated from incompatible substances and isolated from sources of sparks and open flames.


UN1911 Diborane, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 2.1-Flammable gas Inhalation Hazard Zone A. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.


A strong reducing agent. Unstable above 8 C. The presence of contaminants may lower the autoigni- tion temperature; ignition may take place at, or below, room temperature. Diborane can polymerize, forming liquid pentaborane (See P:0190). It ignites spontaneously in moist air; and on contact with water, hydrolyzes exothermically forming hydrogen and boric acid. Contact with halogenated compounds (including fire extinguishers) may cause fire and explosion. Contact with aluminum, lithium and other active metals form hydrides which may ignite spontane- ously. Incompatible with aluminum, carbon tetrachloride; nitric acid; nitrogen trifluoride and many other chemicals. Reacts with oxidized surfaces. Attacks some plastics, rubber or coatings.

Waste Disposal

Return refillable compressed gas cylinders to supplier. Incineration with aqueous scrub- bing of exhaust gases to remove B2O3 particulates.

Diborane Preparation Products And Raw materials

Preparation Products

Raw materials



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