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Beryllium borohydride

From Wikipedia, the free encyclopedia
Beryllium borohydride

  Beryllium
  Boron
  Hydrogen
Names
IUPAC name
Beryllium borohydride
Other names
Beryllium tetrahydroborate(1−), Beryllium tetrahydroborate(III)
Identifiers
3D model (JSmol)
UNII
  • InChI=1S/2BH4.Be/h2*1H4;/q2*-1;+2
    Key: ONQXRAXVSQRPSX-UHFFFAOYSA-N
  • [Be+2].[BH4-].[BH4-]
Properties
Be[BH4]2
Molar mass 38.70 g·mol−1
Appearance white crystals
Density 0.604 g/cm3
Melting point 91.3 °C (196.3 °F; 364.4 K)
Boiling point 123 °C (253 °F; 396 K) decomposes
reacts
Solubility soluble in benzene, diethyl ether
Structure
tetragonal
I41cd, No. 110
Thermochemistry
−108 kJ/mol
Hazards
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 0.002 mg/m3
C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be)[1]
REL (Recommended)
Ca C 0.0005 mg/m3 (as Be)[1]
IDLH (Immediate danger)
Ca [4 mg/m3 (as Be)][1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Beryllium borohydride is an inorganic compound with the chemical formula Be[BH4]2.[2]

Preparation

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Beryllium borohydride is formed by the reaction of beryllium hydride with diborane in an ether solution.

It can also be formed by the reaction of beryllium chloride and lithium borohydride in a sealed tube at 120 °C:[2]

BeCl2 + 2 Li[BH4] → Be[BH4]2 + 2 LiCl

Structure

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The chemical formula of beryllium borohydride can be written as Be2+([BH4])2. The crystal structure is made up of a helical polymer of BH4Be and BH4 structure units.[2][3] The borohydride ions, [BH4], adopt a tetrahedral geometry.[3] Beryllium is 6-coordinate and adopts a distorted trigonal prismatic geometry.[2]

Application

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The purest beryllium hydride is obtained by the reaction of triphenylphosphine, PPh3, with beryllium borohydride, Be[BH4]2 at 180 °C:[2]

Be[BH4]2 + 2 PPh3 → 2 Ph3P+BH3 + BeH2

References

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  1. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0054". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b c d e Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 115–116. ISBN 978-0-08-037941-8.
  3. ^ a b Marynick, Dennis S.; Lipscomb, William N. (1 April 1972). "Crystal structure of beryllium borohydride". Inorg. Chem. 11 (4): 820–823. doi:10.1021/ic50110a033.