beryllium borohydride
{{Chembox
| ImageFile1 = Beryllium-borohydride-chain-from-xtal-3D-bs-17.png
| ImageFile2 = Beryllium-borohydride-xtal-packing-3D-bs-17.png
| ImageCaption2 = {{legend|chartreuse|Beryllium}}{{legend|pink|Boron}}{{legend|white|Hydrogen}}
| IUPACName = Beryllium borohydride
| OtherNames = Beryllium tetrahydroborate(1−), Beryllium tetrahydroborate(III)
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo = 17440-85-6
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4GV25JT031
| PubChem = 6101896
| ChemSpiderID = 4809792
| SMILES = [Be+2].[BH4-].[BH4-]
| StdInChI = 1S/2BH4.Be/h2*1H4;/q2*-1;+2
| StdInChIKey = ONQXRAXVSQRPSX-UHFFFAOYSA-N
}}
| Section2 = {{Chembox Properties
| Formula = {{chem2|Be[BH4]2}}
| Be=1|B=2|H=8
| Appearance = white crystals
| Density = 0.604 g/cm3
| MeltingPtC = 91.3
| BoilingPtC = 123
| BoilingPt_notes = decomposes
| Solubility = reacts
| SolubleOther = soluble in benzene, diethyl ether
}}
| Section3 = {{Chembox Structure
| CrystalStruct = tetragonal
| SpaceGroup = I41cd, No. 110
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = −108 kJ/mol
}}
| Section5 =
| Section6 =
| Section7 = {{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
| REL = Ca C 0.0005 mg/m3 (as Be){{PGCH|0054}}
| PEL = TWA 0.002 mg/m3
C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be)
}}
}}
Beryllium borohydride is an inorganic compound with the chemical formula {{chem2|Be[BH4]2|auto=1}}.{{Greenwood&Earnshaw2nd|pages=115–116}}
Preparation
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:
:{{chem2|BeCl2 + 2 Li[BH4] → Be[BH4]2 + 2 LiCl}}
Structure
The chemical formula of beryllium borohydride can be written as {{chem2|Be(2+)([BH4]−)2}}. The crystal structure is made up of a helical polymer of {{chem2|BH4Be}} and {{chem2|BH4}} structure units.{{cite journal | first1 = Dennis S. | last1 = Marynick | first2 = William N. | last2 = Lipscomb | authorlink2 = William Lipscomb | title = Crystal structure of beryllium borohydride | journal = Inorg. Chem. | date = 1 April 1972 | volume = 11 | issue = 4 | pages = 820–823 | doi = 10.1021/ic50110a033}} The borohydride ions, {{chem2|[BH4]−}}, adopt a tetrahedral geometry. Beryllium is 6-coordinate and adopts a distorted trigonal prismatic geometry.
Application
The purest beryllium hydride is obtained by the reaction of triphenylphosphine, {{chem2|PPh3}}, with beryllium borohydride, {{chem2|Be[BH4]2}} at 180 °C:
:{{chem2|Be[BH4]2 + 2 PPh3 → 2 Ph3P+\s−BH3 + BeH2}}
References
{{reflist}}
{{Beryllium compounds}}
{{Inorganic-compound-stub}}