Diammoniate of diborane

Amine—Boronium Cations. The most extensively studied boronium cation is the diammoniate of diborane [23777-63-1] (16—18). 

This works well for all nido- and arachno-boranes but not for the c/o o-dianions, which are much less reactive. Reactions of B2H6 with NH3 are complex and, depending on the conditions, yield aminodiborane, H2B(/r-H)(/r-NH2)BH2, or the diammoniate of diborane, [BH2(NH3)2]-[BH4] (p. 165) at higher temperatures the benzene analogue borazine, (HNBH)3, results (see p. 210). 

Shore, S. G., and R. W. Parry Chemical Evidence for the Structure of the Diammoniate of Diborane , III. The Reactions of Borohydride Salts with Eithium Halides and Aluminium Chloride. J. Amer. chem. Soc. 80, 12 (1958). 

The diammoniate of diborane, which was first prepared by Stock and Kuss in 1923, is formed as the sole reaction product on introduction of gaseous diborane, diluted with nitrogen, into liquid ammonia at —78°. While previous methods allowed the preparation of only small amounts of the compound, scaling of the present procedure to yield practically any desired quantity appears to be possible. Of the several laboratory methods available for generating diborane, a procedure adapted from the method of Shapiro and co-workers is described below. 

Discovery of the diammoniate of diborane (B2He, 2NH3) and bor-azene (B3N3H6), better known by its older name of borazole, by Stock (131) indicated that the boron hydrides could be used to prepare interesting boron-nitrogen compounds. This approach to boron chemistry was rapidly extended when the principles discussed in the preceding section were clearly recognized. Thus the compound (CH3)3N BH3, the first borane adduct to be characterized (39), pointed the way to the synthesis of a number of similar substances directly from diborane and amines for exam-... 

Parry, R. W. Shore, S. G., Chemical evidence for the structure of the diammoniate of diborane. III. The reactions of borohydride salts with lithium halides and aluminum chloride, J. Am. Chem. Soc. 1958, 80, 15-20. 

---