:Mercury(II) cyanide
{{chembox
| Watchedfields = changed
| verifiedrevid = 443612205
| ImageFile = Mercury(II)-cyanide-3D-vdW.png
| ImageFile2 = Mercuric cyanide.png
| ImageSize =
| IUPACName = dicyanomercury
| OtherNames = mercuric cyanide; cyanomercury; neutral mercury cyanide (1:2); mercury dicyanide; hydrargyri cyanidum"Hydrargyrum. Mercury. Part 5." http://chestofbooks.com/health/materia-medica-drugs/Manual-Pharmacology/Hydrargyrum-Mercury-Part-5.html (accessed April 1, 2009). (homeopathy)
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 592-04-1
| Beilstein = 3679510
| ChEBI = 36573
| ChemSpiderID = 11103
| EC_number = 209-741-6
| Gmelin = 2563
| PubChem = 11591
| UNNumber = 1636
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = RWG7BD1032
| SMILES = C(#N)[Hg]C#N
| InChI = 1/2CN.Hg/c2*1-2;/rC2HgN2/c4-1-3-2-5
| InChIKey = FQGYCXFLEQVDJQ-RYFBSBGDAX
| StdInChI = 1S/2CN.Hg/c2*1-2;
| StdInChIKey = FQGYCXFLEQVDJQ-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| Formula = Hg(CN)2
| MolarMass = 252.63 g/mol
| Appearance = colorless crystals or white powder
| Odor = odorless
| Density = 3.996 g/cm3
| MeltingPtC = 320
| MeltingPt_notes = (decomposes)
| BoilingPt =
| Solubility = 9.3 g/100 mL (14 °C)
53.9 g/100 mL (100 °C)
| SolubleOther = 25 g/100 mL (methanol, 19.5 °C)
soluble in ethanol, ammonia, glycerin
slightly soluble in ether
insoluble in benzene
| RefractIndex = 1.645
| MagSus = −67.0·10−6 cm3/mol
}}
|Section3={{Chembox Hazards
| MainHazards = Highly toxic
| LD50 = 26 mg/kg
| GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|300|301|310|330|373|410}}
| PPhrases = {{P-phrases|260|262|264|270|271|273|280|284|301+310|302+350|304+340|310|314|320|322|330|361|363|391|403+233|405|501}}
| NFPA-H = 4
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = POI
| FlashPt =
| AutoignitionPt =
}}
Mercury(II) cyanide, also known as mercuric cyanide, is a poisonous compound of mercury and cyanide. It is an odorless, toxic white powder. It is highly soluble in polar solvents such as water, alcohol, and ammonia, slightly soluble in ether, and insoluble in benzene and other hydrophobic solvents.Kocovsky, P., G. Wang, and V. Sharma. "Mercury(II) Cyanide." e-EROS Encyclopedia of Reagents for Organic Synthesis. Chichester, UK: John Wiley & Sons, Ltd., 2001. http://www.mrw.interscience.wiley.com/eros/articles/rm034/sect0-fs.html
Molecular and crystal structure
At ambient temperature and ambient pressure, Hg(CN)2 takes the form of tetragonal crystals. These crystals are composed of nearly linear Hg(CN)2 molecules with a C-Hg-C bond angle of 175.0° and an Hg-C-N bond angle of 177.0° (AylettAylett, B.J. "Mercury (II) Pseudohalides: Cyanide, Thiocyanate, Selenocyanate, Azide, Fulminate." Comprehensive Inorganic Chemistry 3:304-306. J.C. Bailar, Harry Julius Emeléus, Sir Ronald Nyholm, and A.F. Trotman-Dickenson, ed. Oxford: Pergamon Press, 1973; distributed by Compendium Publishers (Elmsford, NY), p. 304. gives slightly different values of 189° and 175°, respectively). Raman spectra show that the molecules distort at higher pressures. Between 16-20 kbar, the structure undergoes a phase transition as the Hg(II) center changes from 2- to 4-coordinate as the CN groups bind to neighboring Hg centers forming via Hg-N bonds. The coordination geometry thus changes from tetragonal to tetrahedral, forming a cubic crystal structure, analogous to the structure of Cd(CN)2. Due to the ambidentate nature of the CN ligands, this tetrahedral structure is distorted, but the distortion lessens with increasing pressure until the structure becomes nearly perfectly tetrahedral at >40 kbar.Wong, P.T.T. J. Chem. Phys. 1984, 80(12), 5937-41.
As in the solid state, in aqueous solution, Hg(CN)2 molecules are linear.
Synthesis
Mercuric cyanide is formed from aqueous hydrogen cyanide and mercuric oxide:{{cite book|author1=F. Wagenknecht|author2=R. Juza|chapter=Mercury (II) cyanide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY,NY|volume=2pages=1021}}
:{{chem2|HgO + 2 HCN -> Hg(CN)2 + H2O}}
Hg(CN)2 can also be prepared by mixing HgO with finely powdered Prussian blue.Miller, W.L. Elements of Chemistry: Organic chemistry, 5th ed. New York: John Wiley & Sons, 1880, p. 100. In addition, it can be produced by treating mercuric sulfate with potassium ferrocyanide in water:
:{{chem2|K4Fe(CN)6 + 3 HgSO4 → 3 Hg(CN)2 + 2 K2SO4 + FeSO4}}
Another method to generate mercuric cyanide is through the disproportionation of mercury(I) derivatives. In these reactions, metallic mercury precipitates, and Hg(CN)2 remains in solution:
: Hg2(NO3)2 + 2 KCN → Hg + Hg(CN)2 + 2 KNO3
Reactions
It rapidly decomposes in acid to give off hydrogen cyanide. It is photosensitive, becoming darker in color.Brunton, L.T. A Text-Book Of Pharmacology, Therapeutics And Materia Medica. London: MacMillan & Co., 1885.
Mercury cyanide catalyzes the Koenigs–Knorr reaction for the synthesis of glycosides.
Cyanogen, (CN)2, forms upon heating dry mercury cyanide, but the method is inferior to other routes:Brotherton, T.K.; Lynn, J.W. Chemical Reviews 1959, 59(5), 841-883, 844-846.
: Hg(CN)2 → (CN)2 + Hg
It serves as a source of Hg2+ in its reaction with sodium tetracarbonylcobalt:{{cite journal |doi=10.1039/J19680001005 |title=The Crystal and Molecular Structure of Bis(tetracarbonylcobalt)mercury, Hg[Co(CO)4]2 |date=1968 |last1=Sheldrick |first1=G. M. |last2=Simpson |first2=R. N. F. |journal=Journal of the Chemical Society A: Inorganic, Physical, Theoretical |page=1005 }}
:{{chem2|Hg(CN)2 + 2 NaCo(CO)4 -> Hg[Co(CO)4]2 + 2 NaCN}}
Coordination polymers can be synthesized from Hg(CN)2 building blocks. Large single crystals of [(tmeda)Cu-[Hg(CN)2]2][HgCl4] form upon treating CuCl2, the soft Lewis acid Hg(CN)2, and N,N,N',N'-tetramethylethylenediamine (TMEDA). The migration of two labile chloride ligands from harder Cu(II) to softer Hg(II) drives the formation of the crystal.{{cite journal |doi=10.1021/cm021716r|title=Synthesis, Structure, and Properties of [(tmeda)Cu[Hg(CN)2]2][HgCl4]: A Non-Centrosymmetric 2-D Layered System that Shows Strong Optical Anisotropy|year=2003|last1=Draper|first1=Neil D.|last2=Batchelor|first2=Raymond J.|last3=Sih|first3=Bryan C.|last4=Ye|first4=Zuo-Guang|last5=Leznoff|first5=Daniel B.|journal=Chemistry of Materials|volume=15|issue=8|pages=1612–1616}}
Past applications
The use of mercuric cyanide as an antiseptic was discontinued due to its toxicity.Benaissa, M.L.; Hantson, P.; Bismuth, C.; Baud, F.J. Intensive Care Med. 1995, 21(12), 1051-1053. Hg(CN)2 is also used in photography."Cyanides, Cyanide Oxides and Complex Cyanides." http://www.dncustoms.gov.vn/web_eglish/bieu_thue/E_HTM/E2837.HTM {{Webarchive|url=https://web.archive.org/web/20171230172341/https://www.dncustoms.gov.vn/web_eglish/bieu_thue/E_HTM/E2837.HTM |date=2017-12-30 }} (accessed April 30, 2009).
Toxicology
{{see also|Mercury poisoning|cyanide poisoning}}
Mercury(II) cyanide is poison with health hazard classification 3, having an oral LD50 of 33 milligrams per kilogram in mice and a subcutaneous LD50 of 2.7 milligrams per kilogram in dogs.{{Cite web|url=https://pubchem.ncbi.nlm.nih.gov/compound/mercuric_cyanide#section=Non-Human-Toxicity-Excerpts|title=Mercuric cyanide|last=Pubchem|website=pubchem.ncbi.nlm.nih.gov|language=en|access-date=2018-03-22}}
References
External links
{{Commons category|Mercury(II) cyanide}}
- [https://web.archive.org/web/20060517035532/http://www.npi.gov.au/database/substance-info/profiles/29.html National Pollutant Inventory: Cyanide compounds fact sheet]
- [https://web.archive.org/web/20060425193836/http://www.npi.gov.au/database/substance-info/profiles/53.html National Pollutant Inventory: Mercury and compounds fact sheet]
{{Mercury compounds}}
{{Cyanides}}