B2H6. Tetraborane

Interest in the photochemistry of boron compounds dates back as far as 1913 when Alfred Stock investigated the effects of light from a mercury vapor lamp on diboran 6) and on tetraboran 10). In the case of diborane(6) he commented UV light will also decompose B2H6. The volume of a sample in a quartz tube increased by 1/6 after 24 hours exposure to a mercury-arc lamp, and a pale yellow crystalline substance appeared. Stock also observed that B4H q decomposition to B2H is not noticeably influenced by sunlight. 

Heating B2H6 above 100°C leads to pyrolysis and generates a variety of more complex boranes of which tetraborane(lO) B4H10 and decabomae(14) B10H14 are the most stable. Other reactions can lead to anionic species, such as the icosahedral dodecahydrodecaborate (2-) [BI2H12]2-, prepared at 180°C ... 

The actual chemical structures of boron hydrides remained a mystery for decades. The obvious analogy of the formula of diborane(6), B2H6, to ethane and of tetraborane(lO), B4H10, to butane tempted speculation that the structures were also analogous. In fact, electron diffraction studies appeared to bear this out for B2H6, whieh was incorrectly reported to have the ethane structure. 

The n = 4 case results in the even less well known tetraborane(12)—four borons want but 10 hydrogens. That the stoichiometries of two of the earliest known boron hydrides, B2H6 and B4H10, are so familiar from hydrocarbon chemistry, and the formulas of other boron hydrides even more distinct, no doubt added to considering even these boron compounds as exotic. The simplest structure for diborane(6), long known to be wrong, is that of an... 

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