1,3-Bis(dicyanomethylene)squarate

1,3-Bis(dicyanomethylene)squarate is a divalent anion with chemical formula C10N4O2−2 or ((N≡C−)2C=)2(C4O2)2−.

It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the squarate oxocarbon anion C4O2−4 through the replacement of two opposite oxygen atoms by dicyanomethylene groups =C(−C≡N)2.

The anion can be obtained by reacting squaric acid with aniline to form 1,3-dianiline squarate (a yellow solid), before treating the diester with malononitrile (N≡C−)2CH2 and sodium ethoxide to give the disodium tetrahydrate salt 2Na+·C10N4O2−2·4H2O, an orange water-soluble solid.

The hydrated salt loses the water below 100 °C, but the resulting anhydrous salt is stable up to 400 °C.

[1] Reaction of the sodium salt with salts of other cations in ethanol affords the following salts:[1] Nuclear magnetic resonance shows that the aromatic character of the squarate core is retained.