Title: Diborane(6)
CAS Registry Number: 19287-45-7
Additional Names: Boroethane; diboron hexahydride
Molecular Formula: B2H6
Molecular Weight: 27.67
Percent Composition: B 78.14%, H 21.86%
Literature References: Review of methods of prepn: Adams in Borax to Boranes, Advances Chem. Ser. No. 32 (American Chemical Society, 1961) pp 60-68. Review of structure and properties: Campell, Jr. in Progress in Boron Chemistry vol. 1, Steinberg, McCloskey, Eds. (Macmillan, New York, 1964) pp 167-184. Reviews of reaction chemistry: Schenker, Angew. Chem. 73, 81-107 (1961); Long in Adv. Inorg. Chem. Radiochem. 16, 201-296 (1974). Review of toxicity: see Decaborane(14). General reviews: Stock, Hydrides of Boron and Silicon (Cornell Univ. Press, Ithaca, 1933), passim; Siegel, Mack, J. Chem. Educ. 34, 314-317 (1957); Major, Chem. Eng. Prog. 54(3), 49-54 (1958); Mikhailov, Usp. Khim. 31, 417-451 (1962); Russian Chem. Rev. (Eng. Ed.) 31, 224-235 (1962); Adams, Boron, Metallo-Boron Compounds and Boranes (Interscience, New York, 1964) pp 555-605; Lipscomb, Boron Hydrides (Benjamin, New York, 1963) passim; Long, Prog. Inorg. Chem. 15, 1-99 (1972); Greenwood in Comprehensive Inorganic Chemistry vol. 1, J. C. Bailar, Jr., et al., Eds. (Pergamon Press, Oxford, 1973) pp 763-783.
Properties: Colorless, flammable gas; repulsive, sickly-sweet odor. mp -165°; bp -92.5°. d-112 0.447; d-29.6 0.33; d15.0 0.210. Critical temp 16.7°; critical press. 39.5 atm; Cp at 25°: 13.60 cal/mole/°C. Dec at red heat to B + H2, at lower temps to H2 and other boron hydrides. Spontaneous ignition temp in air about 40-50°; presence of contaminants may lower the temp limit so that ignition or detonation of diborane(6)-air mixtures may occur at or below room temp. Hydrolyzes in water to H2 + H3BO3. Sol in CS2. Reacts with NH3 to form diborane diammoniate; reacts slowly with Br2 and explosively with Cl2 to form boron halides; reacts with hydrocarbons or organoboron compds to give alkyl- or arylboron compds; reacts with metal alkyls to form metal borohydrides; reacts with strong electron pair donors to form borane addn compds.
Melting point: mp -165°
Boiling point: bp -92.5°
Density: d-112 0.447; d-29.6 0.33; d15.0 0.210
CAUTION: Potential symptoms of overexposure are tightening of chest, precordial pain, shortness of breath, nonproductive cough and nausea; headache, lightheadedness, vertigo, chills, fever, fatigue, weakness, tremor and muscle fasciculation. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 92. See also Patty's Industrial Hygiene and Toxicology vol. 2B, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 3rd ed., 1981) pp 2987, 2990-2992.
Use: As catalyst for olefin polymerization; as rubber vulcanizer; as reducing agent; as flame-speed accelerator; in rocket propellants; in intermediate in prepn of the boron hydrides; in conversion of olefins to trialkylboranes and primary alcohols; as a doping gas. |