Hydrazine-mono- and -bisborane

The preparations described below represent a balance among the several rate factors, the availability of starting materials, and the over-all convenience of the procedure. In particular, the use of sodium tetrahydroborate instead of lithium tetrahydroborate eliminates both the handling of a pyrophor and the contamination of the products with ether-soluble lithium salts. 

Caution. The products are shock-sensitive and flammable materials. Shielding should be used in following the procedures for both Parts A and B, 

Although good results may be obtained by conducting the preparation in the open with reagents and solvents as received from the supplier, a product of enhanced stability is obtained if the reagents are dried in vacuo (sodium tetra-hydroborate at 100°, hydrazinium chloride at room temperature), the solvent is dried with calcium hydride, and the entire procedure is carried out under dry nitrogen. The use of an excess of the hydrazine salt also leads to a more stable product. 

The product may also be isolated by precipitation in a large volume of pentane, but this can lead to oiling out, a phenomenon common with low-melting solids. 

Caution, Hydrazine-hishorane does not melt up to 100° and may explode violently if heated rapidly much beyond 100°. The hisborane may also be detonated by impact. Both the monoborane and the bisborane are extremely flammable but not pyrophoric. Shielding and remote-control manipulation are recommended. 

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Diamminedihydroboron(l-I-) tetrahydroborate, synthesis 2 Trimethylamine-borane, (dimethylamino)borane, and N,N, JV"-trimethylborazine, synthesis 3 Hydrazine-mono- and -bisborane, synthesis 4 Diphenylphosphine and dimeric (diphenylphosphino)boranes, S3mthesis 6... 

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