Isolation and some properties of the borane B 16 H 20 are described, obtained by pyrolysis of B 9 H 13 S(CH 3 h· .Even when boranes have been known for more than 60 years, only about 15 species have been isolated and fairly characterized 1 ,2, some of which possess only restricted stability. Most of the boranes are formed by stepwise addition of smaller borane fragments (from Bl to Bs) which imposes limitation, reached usually with the Bl OH14 borane; the latter borane reacts with lower boranes under formation of polymerized species; thus, the method fails to afford higher boranes in isolable quantities. The synthesis of boranes having more than 10 boron atoms in their molecule must followingly be based on principles that will allow a direct addition of fragments or boranes, which have been prepared prior to the actual addition (formation ofBlSH22 (see 3 ) and B 20 H 16 (see 4 ,s), or, on principles of degradation of their derivatives (formation of BlSH22 and i-BlSH22 in the solvolysis 6 of B 20 His)'The first alternative has seemed to be rather attractive, i.e., the addition of higher frag~ents, or their addition compounds with Lewis bases. Recently, we have described 3 pyrolysis of B9H13S(CH3h (I), from which a mixture of boranes was isolated, comprising Bl0H14 (II) and B1SH22 (III), and a small amount of some other crystalline substance, which could not be identified owing to the small quantity obtained. The IR spectrum of this substance, however, pointed towards a borane, and the X-ray powder difraction pattern simultaneously indicated that if this be the case, it can not be any borane previously known. Now, we have managed to ascertain the reaction conditions, under which the species is formed in fair yields, and to establish the fact that the species is novel: eikosahydro-hexadecaborane (IV).
