Mercuric cyanide

Mercury(II) cyanide

Names
IUPAC name dicyanomercury
Other names mercuric cyanide; cyanomercury; mercury cyanide; mercury dicyanide; hydrargyri cyanidum
Identifiers
CAS Number	592-04-1 Y
3D model (JSmol)	Interactive image
ChemSpider	11103
ECHA InfoCard	100.008.857
PubChem CID	11591
InChI InChI=1S/2CN.Hg/c2*1-2; Key: FQGYCXFLEQVDJQ-UHFFFAOYSA-N InChI=1/2CN.Hg/c2*1-2;/rC2HgN2/c4-1-3-2-5 Key: FQGYCXFLEQVDJQ-RYFBSBGDAX
SMILES C(#N)[Hg]C#N
Properties
Chemical formula	Hg(CN)2
Molar mass	252.63 g/mol
Appearance	colorless crystals or white powder
Odor	odorless
Density	3.996 g/cm3
Melting point	320 °C (608 °F; 593 K) (decomposes)
Solubility in water	9.3 g/100 mL (14 °C) 53.9 g/100 mL (100 °C)
Solubility	25 g/100 mL (methanol, 19.5 °C) soluble in ethanol, ammonia, glycerin slightly soluble in ether insoluble in benzene
Magnetic susceptibility (χ)	−67.0·10−6 cm3/mol
Refractive index (nD)	1.645
Hazards
NFPA 704	0 3 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Mercury(II) cyanide, also known as mercuric cyanide, is a coordination compound of nitrogen, carbon and mercury. It is a colorless, odorless, toxic white powder with a bitter metallic taste. It has a melting point of 320 °C (608 °F), at which it decomposes and releases toxic mercury fumes. 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. It rapidly decomposes in acid to give off hydrogen cyanide. Samples also decompose when exposed to light, becoming darker in color. It reacts vigorously with oxidizing agents; fusion with metal chlorates, perchlorates, nitrates, or nitrites can cause a violent explosion.

At ambient temperature and ambient pressure, Hg(CN)₂ takes the form of tetragonal crystals. These crystals are composed of nearly linear Hg(CN)₂molecules with a C-Hg-C bond angle of 175.0° and an Hg-C-N bond angle of 177.0° (Aylett 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.