:2-(Dicyanomethylene)croconate

{{Short description|Ion}}

{{Chembox

| ImageFile = 2-dicyanomethylene croconate.svg

| ImageSize =

| ImageName = 2-(dicyanomethylene)croconate dianion

| PIN = 4-(Dicyanomethylene)-3,5-dioxo-1-cyclopentene-1,2-diolate

|Section1={{Chembox Identifiers

| StdInChI = 1S/C8H2N2O4/c9-1-3(2-10)4-5(11)7(13)8(14)6(4)12/h13-14H/p-2

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = UOFODKSWJURJDQ-UHFFFAOYSA-L

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| ChemSpiderID = 26234929

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| PubChem = 139033599

| SMILES = C(#N)C(=C1C(=O)C(=C(C1=O)[O-])[O-])C#N

}}

|Section2={{Chembox Properties

| C=8|N=2|O=4

| Formula_Charge = 2−

}}

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2-(Dicyanomethylene)croconate is a divalent anion with chemical formula {{chem|C|8|N|2|O|4|2-}} or ((N≡C−)₂C=)(C₅O₄)²⁻. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion {{chem|C|5|O|5|2-}} through the replacement of one oxygen atom by a dicyanomethylene group =C(−C≡N)₂.

The anion was synthesized and characterized by A. Fatiadi in 1980, by hydrolysis of croconate violet treated with potassium hydroxide.Alexander J. Fatiadi (1980), "Pseudooxocarbons. Synthesis of 1,2,3-tris(dicyanomethylene)croconate salts. A new bond-delocalized dianion, croconate blue". Journal of Organic Chemistry volume 45, pages 1338–1339. {{doi|10.1021/jo01295a044}}

It gives an orange solution in water.