- Beryllium hydride
Chembox new
Name = Beryllium hydride
ImageFile = Beryllium-hydride-3D-balls.png
ImageName =
Section1 = Chembox Identifiers
CASNo = 7787-52-2
Section2 = Chembox Properties
Formula = BeH2
MolarMass = 11.03 g mol−1
Appearance = amorphous white solidGreenwood&Earnshaw, p. 115]
Density = 0.62-0.65 g cm−3, solid
Solubility =
MeltingPt = 250 °C with decomp.
Section3 = Chembox Structure
Structure =
Section8 = Chembox Related
OtherCations =lithium hydride ,calcium hydride , boron hydrides
OtherCpds =beryllium fluoride Beryllium hydride, BeH2, is a
chemical compound ofberyllium andhydrogen . Unlike the ionically bondedhydride s of the heavier Group 2 elements, beryllium hydride is covalently bonded.Synthesis
BeH2 was first synthesised in 1951 by reacting dimethylberyllium, Be(CH3)2, with
lithium aluminium hydride , LiAlH4 [ cite journal | author = Glenn D. Barbaras, Clyde Dillard, A. E. Finholt, Thomas Wartik, K. E. Wilzbach, and H. I. Schlesinger | year = 1951 | title = The Preparation of the Hydrides of Zinc, Cadmium, Beryllium, Magnesium and Lithium by the Use of Lithium Aluminum Hydride | journal = J. Am. Chem. Soc. | volume = 73 | issue = 10 | pages = 4585–4590 | doi = 10.1021/ja01154a025 ] .Purer BeH2 forms from the
pyrolysis of di-tert-butylberyllium, Be(C(CH3)3)2 at 210 °C [ cite journal | author = G. E. Coates and F. Glockling | year = 1954 | title = Di-tert.-butylberyllium and beryllium hydride | journal = J. Chem. Soc. | pages = 2526–2529 | doi = 10.1039/JR9540002526 ] .The purest beryllium hydride is obtained by the reaction of
triphenylphosphine , PPh3, with beryllium borohydride, Be(BH4)2::Be(BH4)2 + 2PPh3 → 2Ph3PBH3 + BeH2
Structure
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 cite journal | author = G. J. Brendel, E. M. Marlett, and L. M. Niebylski | year = 1978 | title = Crystalline beryllium hydride | journal = Inorg. Chem. | | volume = 17 | issue = 12 | pages = 3589–3592 | doi = 10.1021/ic50190a051 ] , 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 [ cite journal | author = Gordon S. Smith, Quintin C. Johnson, Deane K. Smith, D. E. Cox, Robert L. Snyder, Rong-Sheng Zhou and Allan Zalkin | year = 1988 | title = The crystal and molecular structure of beryllium hydride | journal =Solid State Communications | volume = 67 | issue = 5 | pages = 491–494 | doi = 10.1016/0038-1098(84)90168-6 ] .References
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