Octahydrotriborate is the boron hydride B₃H₈⁻. It forms a variety of salts that are colorless and air-stable. The

tetrabutylammonium Tetrabutylammonium is a quaternary ammonium cation with the formula (C4H9)4sup>+. It is used in the research laboratory to prepare lipophilic salts of inorganic anions. Relative to tetraethylammonium derivatives, tetrabutylammonium salts are more ...

salt is soluble in organic solvents such as

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

and

methylene chloride Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with ...

. The anion is an intermediate is the synthesis of various higher boron hydrides, such as

pentaborane(9) Pentaborane(9) is an inorganic compound with the formula B5H9. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity toward oxygen, it was once evaluated as rocket or jet fue ...

. B₃H₈⁻ can be viewed as the

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

of triborane B₃H₉.

Preparation

Octahydrotriborate is prepared by partial oxidation of

borohydride Borohydride refers to the anion , which is also called tetrahydroborate, and its salts. Borohydride or hydroborate is also the term used for compounds containing , where ''n'' is an integer from 0 to 3, for example cyanoborohydride or cyanotrihyd ...

with iodine or boron trifluoride: :3BH₄⁻ + I₂ → B₃H₈⁻ + 2H₂ + 2I⁻ :5BH₄⁻ + 4BF₃O(C₂H₅)₂ → 2B₃H₈⁻ + 2H₂ + 4O(C₂H₅)₂ + 3BF₄⁻

Structure and reactions

As shown by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

of various salts, B₃H₈⁻ consists of a distorted triangle of three BH₂ vertices. Two edges of the triangle are occupied by bridging hydrides. It is converted to the bromide B₃H₇Br⁻ using HBr (illustrating its hydridic character): :B₃H₈⁻ + HBr → B₃H₇Br⁻ + H₂

Pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...

of this bromide gives

. :5 B₃H₇Br⁻ → 3 B₅H₉ + 5 Br⁻ + 4 H₂ Also consistent with its basicity, B₃H₈^_ functions as a

bidentate ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

in a variety of

coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

es, e.g. Cr(B₃H₈)₂.{{cite journal , doi=10.1021/ja046906c, title=A New Class of CVD Precursors to Metal Borides: Cr(B₃H₈)₂ and Related Octahydrotriborate Complexes, year=2004, last1=Goedde, first1=Dean M., last2=Girolami, first2=Gregory S., journal=Journal of the American Chemical Society, volume=126, issue=39, pages=12230–12231, pmid=15453732

References

Borohydrides