Mercury(II) hydride (systematically named mercurane(2) and dihydridomercury) is an inorganic compound with the chemical formulaHgH 2 (also written as [HgH 2]). It is both thermodynamically and kinetically unstable at ambient temperature, and as such, little is known about its bulk properties. However, it known as a white, crystalline solid, which is kinetically stable at temperatures below −125 °C (−193 °F), which was synthesised for the first time in 1951.[1]
Mercury(II) hydride is the second simplest mercury hydride (after mercury(I) hydride). Due to its instability, it has no practical industrial uses. However, in analytical chemistry, mercury(II) hydride is fundamental to certain forms of spectrometric techniques used to determine mercury content. In addition, it is investigated for its effect on high sensitivity isotope-ratio mass spectrometry methods that involve mercury, such as MC-ICP-MS, when used to compare thallium to mercury.[2]
In solid mercury(II) hydride, the HgH2 molecules are connected by mercurophilic bonds. Trimers and a lesser proportion of dimers are detected in the vapour. Unlike solid zinc(II), and cadmium(II) hydride, which are network solids, solid mercury(II) hydride is a covalently bound molecular solid. This is due to relativistic effects, which also accounts for the relatively low decomposition temperature of -125 °C.[3]
The HgH2 molecule is linear and symmetric in the form H-Hg-H. The bond length is 1.646543 Å. The antisymmetric stretching frequency, ν3 of the bond is 1912.8 cm−1, 57.34473 THz for isotopes 202Hg and 1H.[3] The energy needed to break the Hg-H bond in HgH2 is 70 kcal/mol. The second bond in the resulting HgH is much weaker only needing 8.6 kcal/mol to break. Reacting two hydrogen atoms releases 103.3 kcal/mol, and so HgH2 formation from hydrogen molecules and Hg gas is endothermic at 24.2 kcal/mol.[3]
Biochemistry
Alireza Shayesteh et al conjectured that bacteria containing the flavoprotein mercuric reductase, such as Escherichia coli, can in theory reduce soluble mercury compounds to volatile HgH2, which should have a transient existence in nature.
Production
Mercury(II) chloride reduction
Mercury(II) hydride may be prepared by the reduction of mercury(II) chloride. In this process, mercury(II) chloride and a hydride salt equivalent react to produce mercury(II) hydride according to the following equations, which depend on the stochiometry of the reaction:
2 HgCl 2 + 2 H− → HgCl2− 4 + HgH 2
HgCl 2 + 2 H− → HgH 2 + 2 Cl−
Variations of this method exits where mercury(II) chloride is substituted for its heavier halide homologues.
Direct synthesis
Mercury(II) hydride can also be generated by direct synthesis from the elements in the gas phase or in cryogenic inert gas martices:[3]
Hg → Hg*
Hg* + H 2 → [HgH 2]*
[HgH 2]* → HgH 2
This requires excitation of the mercury atom to the 1P or 3P state, as atomic mercury in its ground-state does not insert into the dihydrogen bond.[3] Excitation is accomplished by means of an ultraviolet-laser,[1] or electric discharge.[3] The initial yield is high; however, due to the product being in an excited state, a significant amount dissociates rapidly into mercury(I) hydride, then back into the initial reagents:
2 [HgH 2]* → 2 HgH + H 2
2 HgH → Hg 2H 2
Hg 2H 2 → 2 Hg + H 2
This is the preferred method for matrix isolation research. Besides mercury(II) hydride, it also produces other mercury hydrides in lesser quantities, such as the mercury(I) hydrides (HgH and Hg2H2).
Reactions
Unpon treatment with a Lewis base, mercury(II) hydride coverts to an adduct. Upon treatment with a standard acid, mercury(II) hydride and its adducts convert either to a mercury salt or a mercuran(2)yl derivative and elemental hydrogen.[citation needed] Oxidation of mercury(II) hydride gives elemental mercury.[citation needed] Unless cooled below −125 °C (−193 °F), mercury(II) hydride decomposes to produce elemental mercury and hydrogen:[4]
HgH 2 → Hg + H2
History
Mercury(II) hydride was successfully synthesized and identified in 1951 by Egon Wiberg and Walter Henle, by the reaction of mercury(II) iodide and lithium tetrahydroaluminate in a mixture of petroleum ether and tetrahydrofuran. In 1993 Legay-Sommaire announced HgH2 production in cryogenic argon and krypton matrices with a KrF laser.[1] In 2004, solid HgH2 was definitively synthesized and consequentially analysed, by Xuefeng Wang and Lester Andrews, by direct matrix isolation reaction of excited mercury with molecular hydrogen.[4] In 2005, gaseous HgH2 was synthesized by Alireza Shayesteh et al, by the direct gas-phase reaction of excited mercury with molecular hydrogen at standard temperature;[5] and Xuefeng Wang and Lester Andrews[4] determined the structure of solid mercury HgH2, to be a molecular solid.
References
^ abcLegay-Sommaire, N.; F. Legay (1993). "Photochemistry in Hg doped matrices. Infrared spectra of mercury hydrides: HgH2, HgD2, HHgD, HgD". Chemical Physics Letters. 207 (2–3): 123–128. Bibcode:1993CPL...207..123L. doi:10.1016/0009-2614(93)87001-j. ISSN 0009-2614.
^Yin, Runsheng; Krabbenhoft, David; Bergquist, Bridget; Zheng, Wang; Lepak, Ryan; Hurley, James (2016). "Effects of mercury and thallium concentrations on high precision determination of mercury isotopic composition by Neptune Plus multiple collector inductively coupled plasma mass spectrometry". Journal of Analytical Atomic Spectrometry. 31 (10): 2060–2068. doi:10.1039/C6JA00107F.
^ abcdefShayesteh, Alireza; Shanshan Yu; Peter F. Bernath (2005). "Gaseous HgH2, CdH2, and ZnH2". Chemistry: A European Journal. 11 (16): 4709–4712. doi:10.1002/chem.200500332. ISSN 0947-6539. PMID 15912545.
^ abcWang, Xuefeng; Andrews, Lester (2005). "Mercury dihydride forms a covalent molecular solid". Physical Chemistry Chemical Physics. 7 (5): 750–9. Bibcode:2005PCCP....7..750W. doi:10.1039/b412373e. ISSN 1463-9076. PMID 19791358.
^Shayesteh, Alireza; Yu, Shanshan; Bernath, Peter F. (2005). "Infrared Emission Spectra and Equilibrium Structures of Gaseous HgH2and HgD2". The Journal of Physical Chemistry A. 109 (45): 10280–10286. Bibcode:2005JPCA..10910280S. CiteSeerX10.1.1.507.4752. doi:10.1021/jp0540205. ISSN 1089-5639. PMID 16833322.
May 05, 2023
mercury, hydride, systematically, named, mercurane, dihydridomercury, inorganic, compound, with, chemical, formula, hgh2, also, written, hgh2, both, thermodynamically, kinetically, unstable, ambient, temperature, such, little, known, about, bulk, properties, h. Mercury II hydride systematically named mercurane 2 and dihydridomercury is an inorganic compound with the chemical formula HgH2 also written as HgH2 It is both thermodynamically and kinetically unstable at ambient temperature and as such little is known about its bulk properties However it known as a white crystalline solid which is kinetically stable at temperatures below 125 C 193 F which was synthesised for the first time in 1951 1 Mercury II hydride NamesIUPAC name Mercury II hydrideOther names Mercurane Mercuric hydrideIdentifiers3D model JSmol Interactive imagePubChem CID 19021138InChI InChI 1S Hg 2HKey JUQLLZUJMFHASM UHFFFAOYSA NSMILES H Hg H PropertiesChemical formula HgH2Molar mass 202 61 g mol 1Related compoundsRelated compounds Zinc hydrideExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Infobox references Mercury II hydride is the second simplest mercury hydride after mercury I hydride Due to its instability it has no practical industrial uses However in analytical chemistry mercury II hydride is fundamental to certain forms of spectrometric techniques used to determine mercury content In addition it is investigated for its effect on high sensitivity isotope ratio mass spectrometry methods that involve mercury such as MC ICP MS when used to compare thallium to mercury 2 Contents 1 Properties 1 1 Structure 1 2 Biochemistry 2 Production 2 1 Mercury II chloride reduction 2 2 Direct synthesis 3 Reactions 4 History 5 ReferencesProperties EditStructure Edit In solid mercury II hydride the HgH2 molecules are connected by mercurophilic bonds Trimers and a lesser proportion of dimers are detected in the vapour Unlike solid zinc II and cadmium II hydride which are network solids solid mercury II hydride is a covalently bound molecular solid This is due to relativistic effects which also accounts for the relatively low decomposition temperature of 125 C 3 The HgH2 molecule is linear and symmetric in the form H Hg H The bond length is 1 646543 A The antisymmetric stretching frequency n3 of the bond is 1912 8 cm 1 57 34473 THz for isotopes 202Hg and 1H 3 The energy needed to break the Hg H bond in HgH2 is 70 kcal mol The second bond in the resulting HgH is much weaker only needing 8 6 kcal mol to break Reacting two hydrogen atoms releases 103 3 kcal mol and so HgH2 formation from hydrogen molecules and Hg gas is endothermic at 24 2 kcal mol 3 Biochemistry Edit Alireza Shayesteh et al conjectured that bacteria containing the flavoprotein mercuric reductase such as Escherichia coli can in theory reduce soluble mercury compounds to volatile HgH2 which should have a transient existence in nature Production EditMercury II chloride reduction Edit Mercury II hydride may be prepared by the reduction of mercury II chloride In this process mercury II chloride and a hydride salt equivalent react to produce mercury II hydride according to the following equations which depend on the stochiometry of the reaction 2 HgCl2 2 H HgCl2 4 HgH2 HgCl2 2 H HgH2 2 Cl Variations of this method exits where mercury II chloride is substituted for its heavier halide homologues Direct synthesis Edit Mercury II hydride can also be generated by direct synthesis from the elements in the gas phase or in cryogenic inert gas martices 3 Hg Hg Hg H2 HgH2 HgH2 HgH2This requires excitation of the mercury atom to the 1P or 3P state as atomic mercury in its ground state does not insert into the dihydrogen bond 3 Excitation is accomplished by means of an ultraviolet laser 1 or electric discharge 3 The initial yield is high however due to the product being in an excited state a significant amount dissociates rapidly into mercury I hydride then back into the initial reagents 2 HgH2 2 HgH H2 2 HgH Hg2 H2 Hg2 H2 2 Hg H2This is the preferred method for matrix isolation research Besides mercury II hydride it also produces other mercury hydrides in lesser quantities such as the mercury I hydrides HgH and Hg2H2 Reactions EditUnpon treatment with a Lewis base mercury II hydride coverts to an adduct Upon treatment with a standard acid mercury II hydride and its adducts convert either to a mercury salt or a mercuran 2 yl derivative and elemental hydrogen citation needed Oxidation of mercury II hydride gives elemental mercury citation needed Unless cooled below 125 C 193 F mercury II hydride decomposes to produce elemental mercury and hydrogen 4 HgH2 Hg H2History EditMercury II hydride was successfully synthesized and identified in 1951 by Egon Wiberg and Walter Henle by the reaction of mercury II iodide and lithium tetrahydroaluminate in a mixture of petroleum ether and tetrahydrofuran In 1993 Legay Sommaire announced HgH2 production in cryogenic argon and krypton matrices with a KrF laser 1 In 2004 solid HgH2 was definitively synthesized and consequentially analysed by Xuefeng Wang and Lester Andrews by direct matrix isolation reaction of excited mercury with molecular hydrogen 4 In 2005 gaseous HgH2 was synthesized by Alireza Shayesteh et al by the direct gas phase reaction of excited mercury with molecular hydrogen at standard temperature 5 and Xuefeng Wang and Lester Andrews 4 determined the structure of solid mercury HgH2 to be a molecular solid References Edit a b c Legay Sommaire N F Legay 1993 Photochemistry in Hg doped matrices Infrared spectra of mercury hydrides HgH2 HgD2 HHgD HgD Chemical Physics Letters 207 2 3 123 128 Bibcode 1993CPL 207 123L doi 10 1016 0009 2614 93 87001 j ISSN 0009 2614 Yin Runsheng Krabbenhoft David Bergquist Bridget Zheng Wang Lepak Ryan Hurley James 2016 Effects of mercury and thallium concentrations on high precision determination of mercury isotopic composition by Neptune Plus multiple collector inductively coupled plasma mass spectrometry Journal of Analytical Atomic Spectrometry 31 10 2060 2068 doi 10 1039 C6JA00107F a b c d e f Shayesteh Alireza Shanshan Yu Peter F Bernath 2005 Gaseous HgH2 CdH2 and ZnH2 Chemistry A European Journal 11 16 4709 4712 doi 10 1002 chem 200500332 ISSN 0947 6539 PMID 15912545 a b c Wang Xuefeng Andrews Lester 2005 Mercury dihydride forms a covalent molecular solid Physical Chemistry Chemical Physics 7 5 750 9 Bibcode 2005PCCP 7 750W doi 10 1039 b412373e ISSN 1463 9076 PMID 19791358 Shayesteh Alireza Yu Shanshan Bernath Peter F 2005 Infrared Emission Spectra and Equilibrium Structures of Gaseous HgH2and HgD2 The Journal of Physical Chemistry A 109 45 10280 10286 Bibcode 2005JPCA 10910280S CiteSeerX 10 1 1 507 4752 doi 10 1021 jp0540205 ISSN 1089 5639 PMID 16833322 Retrieved from https en wikipedia org w index php title Mercury II hydride amp oldid 1088417770, wikipedia, wiki, book, books, library,
