Tetracyanoethylene

Tetracyanoethylene

File:Tetracyanoethylene.png tetracyanoethylene tetracyanoethylene
File:TCNEpowder.jpg
Names
Preferred IUPAC name Ethenetetracarbonitrile
Other names TCNE
Identifiers
CAS Number	670-54-2 checkY
3D model (JSmol)	Interactive image
ChemSpider	12114 checkY
ECHA InfoCard
E number
PubChem CID	12635
UNII	C592309ECU checkY
CompTox Dashboard (EPA)	{{#property:P3117}}
InChI 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
SMILES N#CC(C#N)=C(C#N)C#N
Properties
Chemical formula	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 checkY☒N ?) Infobox references

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.