Mercury(I) hydride

Mercury(I) hydride
Names
	IUPAC name Mercury(I) hydride
	Other names Dimercurane; Mercurous hydride; Mercury monohydride
Identifiers
CAS Number	13966-62-6;
3D model (JSmol)	Interactive image;
PubChem CID	57348259;
	InChI InChI=1S/Hg.H Key: DJSHOLCMNYJYSS-UHFFFAOYSA-N;
	SMILES [Hg][H];
Properties
Chemical formula	HHg
Molar mass	201.600 g·mol−1
Related compounds
Related compounds	Cadmium hydride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Mercury(I) hydride (systematically named mercury hydride) is an inorganic compound with the empirical chemical formula HgH. It has not yet been obtained in bulk, hence its bulk properties remain unknown. However, molecular mercury(I) hydrides with the formulae HgH and Hg
₂H
₂ have been isolated in solid gas matrices. The molecular hydrides are very unstable toward thermal decomposition. As such the compound is not well characterised, although many of its properties have been calculated via computational chemistry.

Molecular forms

History

In 1979 and 1985, Swiss chemical physicists, Egger and Gerber, and Soviet chemical physicists, Kolbycheva and Kolbychev, independently, theoretically determined that it is feasible to develop a mercury(I) hydride molecular laser.

Chemical properties

Mercury(I) hydride is an unstable gas[1] and is the heaviest group 12 monohydride. The composition of mercury(I) hydride is 0.50% hydrogen and 99.50% mercury. In mercury(I) hydride, the formal oxidation states of hydrogen and mercury are −1 and +1, respectively, because of the electronegativity of mercury is lower than that of hydrogen. The stability of metal hydrides with the formula MH (M = Zn-Hg) increases as the atomic number of M increases.

The Hg-H bond is very weak and therefore the compound has only been matrix isolated at temperatures up to 6 K.[2][3] The dihydride, HgH₂, has also been detected this way.

A related compound is bis(hydridomercury)(Hg—Hg) with the formula Hg
₂H
₂, which can be considered to be dimeric mercury(I) hydride. It spontaneously decomposes into the monomeric form.

Radicality

The mercury centre in mercury complexes such as hydridomercury can accept or donate a single electron by association:

HgH + R → HHgR

Because of this acceptance or donation of the electron, hydridomercury has radical character. It is a moderately reactive monoradical.

References

"Mercury hydride". Chemistry WebBook. USA: National Institute of Standards and Technology. Retrieved 14 October 2012.
Aldridge, Simon; Downs, Anthony J. (2001). "Hydrides of the Main-Group Metals: New Variations on an Old Theme". Chemical Reviews. 101 (11): 3305–65. doi:10.1021/cr960151d. PMID 11840988.
Knight, Lon B. (1971). "Hyperfine Interaction, Chemical Bonding, and Isotope Effect in ZnH, CdH, and HgH Molecules". The Journal of Chemical Physics. 55 (5): 2061–2070. Bibcode:1971JChPh..55.2061K. doi:10.1063/1.1676373.

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[1] "Mercury hydride". Chemistry WebBook. USA: National Institute of Standards and Technology. Retrieved 14 October 2012.

[2] Aldridge, Simon; Downs, Anthony J. (2001). "Hydrides of the Main-Group Metals: New Variations on an Old Theme". Chemical Reviews. 101 (11): 3305–65. doi:10.1021/cr960151d. PMID 11840988.

[3] Knight, Lon B. (1971). "Hyperfine Interaction, Chemical Bonding, and Isotope Effect in ZnH, CdH, and HgH Molecules". The Journal of Chemical Physics. 55 (5): 2061–2070. Bibcode:1971JChPh..55.2061K. doi:10.1063/1.1676373.