Chemistry of pentaborane(9)

Abstract

Pentaborane(9), B5H9, has been known for 50 years1 and its structure was determined over 20 years ago,2 but its unusual and interesting chemical properties have been extensively studied only during the last half-dozen years. This Account will summarize the more important reactions of B5H9 and its conjugate base, the octahydropentaborate(l-) anion, BgHg-.In the laboratory BgHg has been handled almost exclusively in high vacuum apparatus3 because of its toxicity, its unpredictable combustibility, and its propensity to detonate unexpectedly in air.4-6 Pentaborane(9) has been commercially prepared by pyrolysis of diborane( 6),5 while laboratory quantities are

[(2-3)Pentaboran(9)yl](triphenylphosphine)gold(I), [Au(B5H8)(C18H15P)]

“…It is well known that pentaborane(9), BsH 9, can be deprotonated with bases such as the hydride ion to yield the BsH ~ anion (Gaines, 1973, and references therein). Reaction of this species with metal halide derivatives leads to complexes where the metal is often inserted into the B 5 framework system (Greenwood & Kennedy, 1982).…”

2,3,4-Tricarba-nido-hexaboranes(7) with a Bridging B−Ethyl−B Moiety

“…in the case of nido-pentaborane (9) derivatives. [12] NMR Spectroscopic Results: The 1 H-, 11 B-and 13 C-NMR data of 7 (Table 1 and Experimental Section) are fully consistent with a 2,3,4-tricarba-nido-hexaborane (7) cage bearing terminal ethyl groups at all boron atoms, a hydrogen at C(4) and a methyl or a ethyl group at C(2) or C(3). There was no indication of the initially expected BϪHϪB group, either in the 1 H-NMR spectra (with or without 11 B decoupling) or in the 11 B-NMR spectra (with and without 1 H decoupling); this evidence definitely precludes the structures 10 and 10Ј.…”

Substitution on Metallaboranes at Boron. Syntheses of closo-1-X-[2,3,4-(η5-C5Me5)3(μ-H)2Co3B2H], X = Cl and OH, and closo-1,5-Cl2-[2,3,4-(η5-C5Me5)3(μ-H)2Co3B2] from closo-[2,3,4-(η5-C5Me5)3(μ-H)2Co3B2H2]

“…Nature of the Chloride-Substitution Reactions. Main group and transition metal halides have been used extensively to catalyze the halogenation and alkylation of borane and carborane cages. ,, A systematic study of the nature of metal halide catalyzed alkylations of pentaborane(9) details the factors important in one class of these reactions …”