A borohydride is a compound containing the tetrahydridoborate(III) ion, B

Boron

Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...

H₄

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

⁻. Borohydride is a term also used for compounds containing BH₃CN^- (cyanotrihydroborate) and BH(C₂H₅)₃^- (triethylborohydride). Such compounds are mainly used as reducing agent

Reducing agent

A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...

s in organic synthesis

Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

. The most important borohydride is sodium borohydride

Sodium borohydride

Sodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are...

, but other salts are well known (see Table).

Coordination complexes

Borohydrides are excellent ligands for metal ions. In most such compounds, the BH₄^- ligand is bidentate. The binary borohydrides containing only BH₄^- ligands are often fairly volatile. One example is uranium borohydride

Uranium borohydride

Uranium borohydride U4 is a volatile uranium complex with borohydride. This green-coloured compound is polymeric in the solid but evaporates to a tetrahedral monomer.-Preparation:...

.

Selected Properties of Various Borohydride Salts

Hydride CAS registry number	Mol.Wt.	Hydrogen Density	Density g/cm3	m.p. (°C)	solubility in water (g/100 mL, 25 °C)	solubility in CH3OH (g/100 mL, 25 °C)	solubility in ether (g/100 mL, 25 °C)	solubility in THF (g/100 mL, 25 °C)
LiBH4 Lithium borohydride Lithium borohydride is a tetrahydroborate and known in organic synthesis as a reducing agent for esters. Although less common than the related sodium borohydride, the lithium salt offers some advantages of being highly soluble in ethers and being a stronger reducing agent but still safer to... [16949-15-8]	21.78	18.5	0.66	280	20.9	decomp. (44 in EtOH)	4.3	22.5
NaBH4 Sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are... [16940-66-2]	37.83	10.6	1.07	505	55	16.4 (20 °C)	insol.	0.1 (20 °C)
NaBH3CN Sodium cyanoborohydride Sodium cyanoborohydride is the inorganic compound with the formula NaBH3. This colourless salt is widely used in organic synthesis for the reduction of imines.-Preparation and use:... [25895-60-7]	62.84	6.4	1.20	240 with deccomp.	deccomp.	217	insol.	36
KBH4 [13762-51-1]	53.94	7.4	1.17	585 (under H2)	19	insol.	insol.	insol.
LiBH(C2H5)3 Lithium triethylborohydride Lithium triethylborohydride , commonly abbreviated to LiTEBH or Superhydride, is a powerful and selective reducing agent used in inorganic and organic chemistry. LiTEBH is far more powerful than lithium borohydride and more powerful than lithium aluminium hydride in many cases... [22560-16-3]	105.94	0.95	unknown	unknown	decomp.	decomp.	na	high (supplied commercially)