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1,3 Bis(dicyanomethylene)squarate

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1,3-Bis(dicyanomethylene)squarate

1,3-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 opposite oxygen atoms by dicyanomethylene groups =C(−C≡N)2.

The anion can be obtained by reacting squaric acid with aniline to form the diester 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+·C
10N
4O2−
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. Reaction of the sodium salt with salts of other cations in ethanol affords the following salts:

  • dipotassium sodium chloride 2K+·Na+·Cl−·K
    2    C
    10    N
    4    O2−
    2    · 1⁄2CH3CN, orange
  • rubidium sodium chloride 7Rb+·Na+·2Cl−·3Rb
    2    C
    10    N
    4    O2−
    2    ·CH
    3    CH
    2    OH    , orange, loses 1 ethanol at 96 °C, stable to 361 °C
  • magnesium disodium nitrate, Mg2+·2Na+C
    10    N
    4    O2−
    2    ·NO−
    3    ·6H2O·CH
    3    CH
    2    OH    , orange, loses 1 ethanol and 6 H2O at 78 °C, stable to 482 °C
  • calcium, Ca2+·C
    10    N
    4    O2−
    2    ·6H2O, purple, dehydrates at 63–102 °C, stable to 468 °C
  • barium, Ba2+·C
    10    N
    4    O2−
    2    ·4H2O, orange, dehydrates at 71–96 °C, stable to 457 °C
  • tetra-n-butylammonium sodium, 2(C
    4    H
    9    )4N+·2Na+·2Cl−·2C
    10    N
    4    O2−
    2    ·CH
    3    CH
    2    OH    , orange, loses 1 ethanol and 2 tetrabutylammonium at 111 °C, stable to 238 °C

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

    References

    1,3-Bis(dicyanomethylene)squarate Wikipedia
    (Text) CC BY-SA