Diborane precautions

CAUTION Diborane is a toxic gas which bums explosively in air. Its handling requires adequate precautions . 

A boron analog - sodium borohydride - was prepared by reaction of sodium hydride with trimethyl borate [84 or with sodium fluoroborate and hydrogen [55], and gives, on treatment with boron trifluoride or aluminum chloride, borane (diborane) [86. Borane is a strong Lewis acid and forms complexes with many Lewis bases. Some of them, such as complexes with dimethyl sulfide, trimethyl amine and others, are sufficiently stable to have been made commercially available. Some others should be handled with precautions. A spontaneous explosion of a molar solution of borane in tetrahydrofuran stored at less than 15° out of direct sunlight has been reported [87]. 

Impure diborane is a hazardous material and may combust explosively on contact with air. Therefore, precautions must be taken to prevent escape from the reaction. 

The addition of a gas to a reaction mixture (commonly the hydrogen halides, fluorine, chlorine, phosgene, boron trifluoride, carbon dioxide, ammonia, gaseous unsaturated hydrocarbons, ethylene oxide) requires the provision of safety precautions which may not be immediately apparent. Some of these gases may be generated in situ (e.g. diborane in hydroboration reactions), some may be commercially available in cylinders, and some may be generated by chemical or other means (e.g. carbon dioxide, ozone). An individual description of the convenient sources of these gases will be found under Section 4.2. 

Precautions Diborane is a highly toxic, flammable, and reactive gas. It is spontaneously combustible in moist air and may burn or explode upon contact with halogenated compounds. It explodes on contact with fluorine, chlorine, halogenated hydrocarbons, fuming nitric acid, and nitrogen trifluoride. It is a very dangerous gas and must be handled and used only in chemical laboratories by experienced and trained professional workers. ... 

The general procedure is given in Section 25-A. The reaction vessel should be covered to exclude light and the mercury manometers closed except when the diborane is measured. These two precautions lessen the chance of extensive product decomposition. 

Diborane is valued as a fuel for use in rocket propellants. Gallery Ghemical Co. developed equipment and procedures for the safe handling of diborane and by 1962 had produced about 5 million pounds of the material. It is offered for shipment in chrome-molybdenum steel cylinders at —80° (minimum order 100 g.), and technical bulletins present information on handling procedures and safety precautions. 

Diborane should be handled using the "basie prudent practices" of Chapter 5.C, supplemented by the additional precautions for work with reactive and explosive compounds described in Chapter 5.G. In particular, diborane should be used only in a fume hood free of ignition sources and should be stored in a cold, dry, weU-ventUated area separated from incompatible substances and isolated from sources of sparks and open flames. 

As Stock noted, some of the simpler boranes are dangerously reactive, and proper precautions must be taken when synthesizing them. Diborane, which results when one might expect BH3, can be prepared from various boron(III) compounds, as shown in Equation (14.20) ... 

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