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1,2 Bis(dicyanomethylene)squarate

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1,2-Bis(dicyanomethylene)squarate

1,2-Bis(dicyanomethylene)squarate is a divalent anion with chemical formula C
10N
4O2−
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 C
4O2−
4 through the replacement of two adjacent oxygen atoms by dicyanomethylene groups =C(−C≡N)2.

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+·C
10N
4O2−
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. Reaction of the sodium salt with the chlorides of other cations in ethanol affords the following salts:

  • dipotassium 2K+·K
    2    C
    10    N
    4    O2−
    2    , anhydrous, yellow, stable to 300 °C
  • dirubidium 2Rb+·Rb
    2    C
    10    N
    4    O2−
    2    , anhydrous, brown, stable to 300 °C
  • magnesium sodium chloride, Mg2+·Na+·Cl−·C
    10    N
    4    O2−
    2    · 4 1⁄2H2O, dark yellow, dehydrates at 60–106 °C, stable to 461 °C
  • calcium disodium, 2Na+·Ca2+·2C
    10    N
    4    O2−
    2    ·9H2O, yellow, dehydrates at 50–90 °C, stable to 178 °C
  • barium, Ba2+·C
    10    N
    4    O2−
    2    ·2H2O, yellow, dehydrates at 87 °C, stable to 337 °C
  • tetra-n-butylammonium, 2(C4H5)4N+·C
    10    N
    4    O2−
    2    ·H2O, yellow, dehydrates at 145 °C, stable to 323 °C

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

    References

    1,2-Bis(dicyanomethylene)squarate Wikipedia
    (Text) CC BY-SA