Tetracyanoethylene

Tetracyanoethylene
tetracyanoethylene
tetracyanoethylene
Names
Preferred IUPAC name
Ethenetetracarbonitrile
Other names
TCNE
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.010.527 Edit this at Wikidata
UNII
  • InChI=1S/C6N4/c7-1-5(2-8)6(3-9)4-10 checkY
    Key: NLDYACGHTUPAQU-UHFFFAOYSA-N checkY
  • InChI=1/C6N4/c7-1-5(2-8)6(3-9)4-10
    Key: NLDYACGHTUPAQU-UHFFFAOYAN
  • N#CC(C#N)=C(C#N)C#N
Properties
C2(CN)4
Molar mass 128.094 g·mol−1
Density 1.35 g/cm3
Melting point 199 °C (390 °F; 472 K)
Boiling point 130 to 140 °C (266 to 284 °F; 403 to 413 K) 0.1 mmHg (sublimes)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkYX markN ?)

Tetracyanoethylene (TCNE) is organic compound with the formula C2(CN)4. It is a colorless solid, although samples are often off-white. It is an important member of the cyanocarbons.

Synthesis and reactions

TCNE is prepared by brominating malononitrile in the presence of potassium bromide to give the KBr-complex, and dehalogenating with copper.

Oxidation of TCNE with hydrogen peroxide gives the corresponding epoxide, which has unusual properties.

In the presence of base, TCNE reacts with malononitrile to give salts of pentacyanopropenide:

C2(CN)4 + CH2(CN)2 → [(NC)2C=C(CN)−C(CN)2]− + CN− + 2 H+

Redox chemistry

TCNE is an electron acceptor. Cyano groups have low energy π* orbitals, and the presence of four such groups, with their π systems (conjugated) to the central C=C double bond, gives rise to an electrophilic alkene. TCNE is reduced at −0.27 V vs ferrocene/ferrocenium:

C2(CN)4 + e− → [C2(CN)4]−

Because of its ability to accept an electron, TCNE has been used to prepare numerous charge-transfer salts and magnetic molecular materials.

The central C=C distance in TCNE is 135 pm. Upon reduction, this bond elongates to 141–145 pm, depending on the counterion.

Safety

TCNE hydrolyzes in moist air to give hydrogen cyanide and should be handled accordingly.

References

  1. 1 2 3 Carboni, R. A. (1959). "Tetracyanoethylene". Organic Syntheses. 39: 64. doi:10.15227/orgsyn.039.0064.
  2. ↑ Linn, W. J. (1969). "Tetracyanoethylene Oxide". Organic Syntheses. 49: 103. doi:10.15227/orgsyn.049.0103.
  3. ↑ Middleton, W. J.; Wiley, D. W. (1961). "Tetramethylammonium 1,1,2,3,3-Pentacyanopropenide". Org. Synth. 41: 99. doi:10.15227/orgsyn.041.0099.
  4. ↑ Connelly, N. G.; Geiger, W. E. (1996). "Chemical Redox Agents for Organometallic Chemistry". Chemical Reviews. 96 (2): 877–910. doi:10.1021/cr940053x. PMID 11848774.
  5. ↑ Chittipeddi, Sailesh; Cromack, K. R.; Miller, Joel S.; Epstein, A. J. (1987-06-22). "Ferromagnetism in Molecular Decamethylferrocenium Tetracyanoethenide (DMeFc TCNE)". Physical Review Letters. 58 (25): 2695–2698. Bibcode:1987PhRvL..58.2695C. doi:10.1103/physrevlett.58.2695. ISSN 0031-9007. PMID 10034821.
  6. ↑ Becker, P.; Coppens, P.; Ross, F. K. (1973). "Valence electron distribution in cubic tetracyanoethylene by the combined use of x-ray and neutron diffraction". Journal of the American Chemical Society. 95 (23): 7604–7609. doi:10.1021/ja00804a010.
  7. ↑ Bock, H.; Ruppert, K. (1992). "Structures of charge-perturbed or sterically overcrowded molecules. 16. The cesium tetracyanoethylenide radical salt". Inorganic Chemistry. 31 (24): 5094–5099. doi:10.1021/ic00050a032.