Beryllium hydride | |
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Identifiers | |
CAS number | 7787-52-2 |
PubChem | 139073 |
ChemSpider | 17215712 |
ChEBI | CHEBI:33787 |
Jmol-3D images | Image 1 |
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Properties | |
Molecular formula | BeH2 |
Molar mass | 11.03 g mol−1 |
Appearance | amorphous white solid[1] |
Density | 0.65 g/cm3 |
Melting point |
250 °C with decomp.[1] |
Solubility in water | decomposes |
Related compounds | |
Other cations | lithium hydride, calcium hydride, boron hydrides |
Related compounds | beryllium fluoride |
(verify) (what is: / ?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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Infobox references |
Beryllium hydride, BeH2, is a chemical compound of beryllium and hydrogen commonly used in rocket fuel.[2] Unlike the ionically bonded hydrides of the heavier Group 2 elements, beryllium hydride is covalently bonded.[1]
BeH2 was first synthesised in 1951 by reacting dimethylberyllium, Be(CH3)2, with lithium aluminium hydride, LiAlH4.[3]
Purer BeH2 forms from the pyrolysis of di-tert-butylberyllium, Be(C(CH3)3)2 at 210 °C.[4]
The purest beryllium hydride is obtained by the reaction of triphenylphosphine, PPh3, with beryllium borohydride, Be(BH4)2[1]:
Note that unlike the other elements in group 2 where the hydride can be prepared by reaction of the elements, the reaction of the metal with hydrogen to produce beryllium hydride has not proved possible.[5]
BeH2 is usually formed as an amorphous white solid, but a hexagonal crystalline form with a higher density (~0.78 g cm−3) was reported,[6] prepared by heating amorphous BeH2 under pressure, with 0.5-2.5% LiH as a catalyst.
A more recent investigation found that crystalline beryllium hydride has a body-centred orthorhombic unit cell, containing a network of corner-sharing BeH4 tetrahedra, in contrast to the flat, hydrogen-bridged, infinite chains previously thought to exist in crystalline BeH2.[7]
Studies of the amorphous form also find that it consists of a network of corner shared tetrahedra.[8]
Molecular BeH2 has been confirmed in a recent study as linear with a Be-H bond length of 133.376 pm. [9]
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