1,3-Bis(dicyanomethylene)squarate

1,3-Bis(dicyanomethylene)squarate is a divalent anion with chemical formula or ((N≡C−)C=)(CO). It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the squarate oxocarbon anion through the replacement of two opposite oxygen atoms by dicyanomethylene groups =C(−C≡N).

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−)CH and sodium ethoxide to give the disodium tetrahydrate salt 2Na··4HO, an orange water-soluble solid. The hydrated salt loses the water below 100 Ã‚°C, but the resulting anhydrous salt is stable up to 400 Ã‚°C. Reaction of the sodium salt with salts of other cations in ethanol affords the following salts:

• dipotassium sodium chloride 2K·Na·Cl··CHCN, orange
• rubidium sodium chloride 7Rb·Na·2Cl·3·, orange, loses 1 ethanol at 96 Ã‚°C, stable to 361 Ã‚°C
• magnesium disodium nitrate, Mg·2Na··6HO·, orange, loses 1 ethanol and 6 HO at 78 Ã‚°C, stable to 482 Ã‚°C
• calcium, Ca··6HO, purple, dehydrates at 63–102 Ã‚°C, stable to 468 Ã‚°C
• barium, Ba··4HO, orange, dehydrates at 71–96 Ã‚°C, stable to 457 Ã‚°C
• tetra-n-butylammonium sodium, 2()N·2Na·2Cl·2·, orange, loses 1 ethanol and 2 tetrabutylammonium at 111 Ã‚°C, stable to 238 Ã‚°C

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

See also

• Croconate violet
• Croconate blue
• 1,2-Bis(dicyanomethylene)squarate

References