Chromium(II) hydride
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Other names
Chromium dihydride
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3D model (
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PubChem CID
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Properties | |
CrH2 | |
Molar mass | 54.0040 g/mol |
Appearance | brown solid |
Related compounds | |
Related compounds
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chromium(I) hydride Chromium hydride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chromium(II) hydride, systematically named chromium dihydride and poly(dihydridochromium) is pale brown solid inorganic compound with the chemical formula (CrH2)n (also written ([CrH2])n or CrH2). Although it is thermodynamically unstable toward decomposition at ambient temperatures, it is kinetically metastable.
Chromium(II) hydride is the second simplest polymeric chromium hydride (after chromium(I) hydride). In metallurgical chemistry, chromium(II) hydride is fundamental to certain forms of chromium-hydrogen alloys.
Nomenclature
The most common name for chromium(II) hydride is chromium dihydride, following the
Monomer
The chromium(II) hydride monomer, is both thermodynamically and kinetically unstable towards autopolymerization at ambient temperature, and so cannot be concentrated. Nevertheless, molecules of CrH2 and Cr2H4 have been isolated in solid gas matrices.[1]
Cr is the second simplest molecular chromium hydride (after Chromium(I) hydride). In the presence of pure hydrogen, dihydridochromium readily converts to bis(dihydrogen)dihydridochromium, CrH2(H2)2 in an exothermic reaction.[1]
Properties
Structure
In diluted CrH2, the molecules are known to oligomerise forming at least Cr2H4 (
Production
The dimer is produced synthetically by hydrogenation. In this process, chromium and hydrogen react according to the reaction:
- Cr + H2 → HCr(μ-H)2CrH[1]
This process involves atomic chromium as an intermediate, and occurs in two steps. The hydrogenation (step 2) is a spontaneous process.
- Cr (s) → Cr (g)
- Cr (g) + H2 (g) → HCr(μ-H)2CrH (g)
In an inert gas matrix atomic Cr reacts with H2 to make the dihydride when it is irradiated with
History
In 1979 the simplest molecular chromium(II) hydride with the chemical formula CrH2 (systematically named dihydridochromium) was synthesised and identified for the first time. It was synthesised directly from the elements, in a reaction sequence which consisted of simultaneous sublimation of chromium to atomic chromium and thermolysis of hydrogen, and concluded with co-deposition in a cryogenic argon matrix to form dihydridochromium.[3]
In 2003 the dimer with the chemical formula HCr(μ-H)2CrH (systematically named di-μ-hydrido-bis(hydridochromium)) was synthesised and identified for the first time. It was also synthesised directly from the elements, in a reaction sequence which consisted of
References
- ^ .
- ^ .
- doi:10.1063/1.438596.