Decahydrodecaborate dianion

Azo coupling reactions with the polyhedral boron hydride decahydrodecaborate dianion B10Hio"" (12.164, Fig. 12-9) were discovered by Hawthorne and Olsen (1964, 1965). 

Fig. 12-9. Stereochemical structure of the decahydrodecaborate dianion (B10H o, 12.164 after Dobrott and Lipscomb, 1962).

Here, we discuss the diazoboranes. They were discovered in Muetterties group. In their first paper (Knoth et al., 1964), they described the reaction of the diammonium salt of decahydrodecaborate dianion (3.10) with excess nitrous acid (10-12 equiv.) in aqueous solution (3-16). A brown solid precipitate was obtained that was very difficult to handle because it detonated extremely readily. Yet, it rapidly forms the bis-diazonium inner salt 3.11 when reduced with sodium borohydride. 

The decahydrodecaborate dianion (3.10) displays a close, bicapped, Archimedian anti-prismatic framework (Fig. 3-1), confirmed by X-ray crystallography (Dobrott and Lipscomb, 1962). Reactions take place at the apical sites first. 

---