1,2-Bis(dicyanomethylene)squarate

1,2-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 adjacent oxygen atoms by dicyanomethylene groups =C(−C≡N)2.

Nuclear magnetic resonance shows that the aromatic character of the squarate core is retained.

[1] The anion can be obtained by reacting squaric acid with n-butanol to obtain the diester 1,2-dibutyl squarate (an oily orange liquid) and treating the latter with metallic sodium and malononitrile (N≡C−)2CH2 to give the trihydrated disodium salt 2Na+·C10N4O2−2·3H2O, a yellow water-soluble solid.

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