Tetracyanoethylene
Template:Short description Template:Chembox
Tetracyanoethylene (TCNE) is organic compound with the formula Template:Chem2. 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.[1]
Oxidation of TCNE with hydrogen peroxide gives the corresponding epoxide, which has unusual properties.[2]
In the presence of base, TCNE reacts with malononitrile to give salts of pentacyanopropenide:[3]
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 Template:Chem2 double bond, gives rise to an electrophilic alkene. TCNE is reduced at −0.27 V vs ferrocene/ferrocenium:[4]
Because of its ability to accept an electron, TCNE has been used to prepare numerous charge-transfer salts[5] and magnetic molecular materials.
The central C=C distance in TCNE is 135 pm.[6] Upon reduction, this bond elongates to 141–145 pm, depending on the counterion.[7]
Safety
TCNE hydrolyzes in moist air to give hydrogen cyanide and should be handled accordingly.[1]
References
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