1,2-Bis(dicyanomethylene)squarate

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

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

Synthesis

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−)CH to give the trihydrated disodium salt 2Na··3HO, a yellow 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.

Salts

Reaction of the sodium salt with the chlorides of other cations in ethanol affords the following salts:

• dipotassium 2K·, anhydrous, yellow, stable to 300 Ã‚°C
• dirubidium 2Rb·, anhydrous, brown, stable to 300 Ã‚°C
• magnesium sodium chloride, Mg·Na·Cl··HO, dark yellow, dehydrates at 60–106 Ã‚°C, stable to 461 Ã‚°C
• calcium disodium, 2Na·Ca·2·9HO, yellow, dehydrates at 50–90 Ã‚°C, stable to 178 Ã‚°C
• barium, Ba··2HO, yellow, dehydrates at 87 Ã‚°C, stable to 337 Ã‚°C
• tetra-n-butylammonium, 2(CH)N··HO, yellow, dehydrates at 145 Ã‚°C, stable to 323 Ã‚°C

See also

• Croconate violet
• Croconate blue
• 1,3-Bis(dicyanomethylene)squarate

References