Lithium borohydride

Crystal structure
__ Li + __ H __ B 3+
Crystal system	orthorhombic
Space group	Pnma (No. 62)
Lattice parameters	a = 7.17858 (4) Å, b = 4.43686 (2) Å, c = 6.80321 (4) Å
General
Surname	Lithium borohydride
other names	Lithium boranate Lithium tetrahydroborate Lithium tetrahydridoborate
Ratio formula	LiBH 4
Brief description	hygroscopic light gray solid
External identifiers / databases
CAS number 16949-15-8 EC number 241-021-7 ECHA InfoCard 100.037.277 PubChem 4148881 Wikidata Q427027
properties
Molar mass	21.78 g mol −1
Physical state	firmly
density	0.6660 g cm −3
Melting point	280 ° C
solubility	easily in water (209 g l −1 at 10 ° C, decomposition) soluble in ether (2.5 g l −1 at 19 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 260-301-311-331-314 EUH: 014 P: 223-231 + 232-261-280-370 + 378-422
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Lithium borohydride is a chemical compound from the group of lithium compounds and boranes .

Extraction and presentation

Lithium borohydride can be produced by a metathesis reaction of sodium borohydride and lithium bromide .

${\displaystyle {\ce {NaBH4 + LiBr -> NaBr + LiBH4}}}$

The direct formation from metallic lithium , boron and hydrogen is possible in principle, but requires extreme conditions (150 at hydrogen pressure, 650 ° C).

Production from (intermediate) diborane (for example from lithium hydride with boron trifluoride in diethyl ether ) is also possible.

${\displaystyle {\ce {2LiH + B2H6 -> 2LiBH4}}}$

properties

Lithium borohydride is a flammable, hygroscopic, white to gray solid. It decomposes on contact with water or moist air and forms hydrogen in the process.

${\displaystyle {\ce {LiBH4 + 2H2O -> LiBO2 + 4H2 ^}}}$

The compound crystallizes at room temperature in the space group Pnma (space group no. 62) with the lattice constants a = 7.17858 (4) Å, b = 4.43686 (2) Å, c = 6.80321 (4) Å in one Orthorhombic distorted wurtzite structure . At higher temperatures there is a hexagonal crystal structure in the space group P 6 ₃ mc (space group no.186 ) with the lattice constants a = 4.27631 (5) Å, c = 6.94844 (8) Å.

use

Lithium borohydride is used as a reducing agent for aldehydes , ketones , lactones , epoxides and esters in organic chemistry.

Individual evidence

1. ↑ ^{a b} J-Ph. Soulie, G. Renaudin, R. Cerny, K. Yvon: Lithium borohydride LiBH ₄ : I. Crystal structure . In: Journal of Alloys and Compounds . tape 346 , no. 1– ² , November 18, 2002, pp. 200-205 , doi : 10.1016 / S0925-8388 (02) 00521-2 .
2. ↑ ^{a b c d e f g h} Entry on lithium borohydride in the GESTIS substance database of the IFA , accessed on July 23, 2016(JavaScript required) .
3. ↑ ^{a b} Georg Brauer (Ed.), With the collaboration of Marianne Baudler u a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 793.
4. ↑ Peter Rittmeyer, Ulrich Wietelmann: hydride. In Ullmann's Encyclopedia of Industrial Chemistry . 2002, Wiley-VCH, Weinheim, doi : 10.1002 / 14356007.a13_199 .
5. ↑ ^{a b} Patent DE10302262A1 : Process for the production of lithium borohydride.