Tetracyanoethylene

Tetracyanoethylene (TCNE) is an organic compound consisting of ethylene with the four hydrogen atom replaced with cyano groups. It is an important member of the cyanocarbons.

Redox chemistry
TCNE is often used as an electron acceptor. Cyano groups have low energy π* orbitals, and the presence of four such groups, with their π systems linked (conjugated) to the central C=C double bond, gives rise to an excellent acceptor. Thus, treatment of TCNE with iodide salts gives the radical anion:
 * C2(CN)4 +  I-  &rarr;  [C2(CN)4]-  +  0.5 I2

Because of its planarity and its ability to accept electrons, TCNE has been used to prepare numerous organic superconductors, usually by serving as a single electron oxidant of an organic electron donor. Such charge-transfer salts are sometimes called Bechgaard salt.

Synthesis and reactions
TCNE is prepared from malononitrile

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

Safety
TCNE is a source of HCN and should be handled accordingly.