Tetracyanomethane

Tetracyanomethane or carbon tetracyanide is a percyanoalkane molecular carbon nitride with formula C(CN)4. The structure can be considered as methane with all hydrogen atoms replaced by cyanide groups. It was first made by Erwin Mayer in 1969.[2][3]

Tetracyanomethane
Names
IUPAC name
Methanetetracarbonitrile
Other names
carbon tetracyanide; 2,2-dicyanomalononitrile
Identifiers
3D model (JSmol)
ChemSpider
Properties
C5N4
Molar mass 116.083 g·mol−1
Structure
trigonal
R3c
a = 9.062, c = 11.625
137.8 Å3
6
tetrahedron
Thermochemistry[1]
Std enthalpy of
formation (ΔfH⦵298)
 −146.2 kcal/mol
−616.4 kcal/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Properties

Tetracyanomethane is a solid at room temperature. It decomposes over 160 °C without melting, and although it can be in a dilute vapour, no liquid form is known.[2] The molecules of tetracyanomethane have a tetrahedral symmetry (43m or Td). The molecule has C-C distance of 1.484 Å and C-N distance of 1.161 Å in the gas form. In the solid the C≡N bond shortens to 1.147 Å.[3] The C-C bond has a force constant of 4.86×105 dyn/cm which is slightly greater than the C-Cl bond in carbon tetrachloride, but a fair bit weaker than in the tricyanomethanide ion.[4] At pressures over 7 GPa tetracyanomethane starts to polymerize to form a disorganised covalent network solid. At higher pressure the colour yellows and darkens to black. Over 20 GPa the polymerization is total.[5]

The bulk modulus K0 = 4.4 and its derivative K0' = 18.[5]

Production

Tetracyanomethane can be made by reacting cyanogen chloride with silver tricyanomethanide.[4]

ClCN + AgC(CN)3 → C(CN)4 +AgCl

Reactions

In an acid solution in water tetracyanomethane is hydrolysed to yield tricyanomethanide and ammonium ions along with carbon dioxide. In alkaline solutions tricyanomethanide and cyanate ions are produced.[4]

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See also

References
  1. Barnes, D.S.; Mortimer, C.T.; Mayer, E. (July 1973). "The enthalpy of formation of tetracyanomethane". The Journal of Chemical Thermodynamics. 5 (4): 481–483. doi:10.1016/S0021-9614(73)80095-3.
  2. Mayer, Erwin (1969). "Darstellung und Eigenschaften von Tetracyanmethan". Monatshefte für Chemie. 100 (2): 462–468. doi:10.1007/BF00904089.
  3. Britton, D. (1 July 1974). "The crystal structure of tetracyanomethane, C(CN)4". Acta Crystallographica Section B. 30 (7): 1818–1821. doi:10.1107/S0567740874005863.
  4. Hester, Ronald E.; Lee, Kenneth Michael; Mayer, Erwin (September 1970). "Tetracyanomethane as a pseudo-(carbon tetrahalide)". The Journal of Physical Chemistry. 74 (18): 3373–3376. doi:10.1021/j100712a011.
  5. Keefer, Derek W.; Gou, Huiyang; Wang, Qianqian; Purdy, Andrew; Epshteyn, Albert; Juhl, Stephen J.; Cody, George D.; Badding, John; Strobel, Timothy A. (12 February 2018). "Tetracyanomethane under Pressure: Extended CN Polymers from Precursors with Built-in sp3 Centers". The Journal of Physical Chemistry A. 122 (11): 2858–2863. doi:10.1021/acs.jpca.7b10729.
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