Wikipedia
In chemistry, methanetetracarboxylate is a tetravalent anion with formula CO or C(COO). It has four carboxylate groups attached to a central carbon atom; so it has the same carbon backbone as neopentane. It is an oxocarbon anion, that is, consists only of carbon and oxygen.
The term is also used for any salt with that anion; or for any ester with the C(COO-) moiety.
Backer, H. J.; Lolkema, J. (1939), Methanetetracarboxylic esters. Recueil des Travaux Chimiques des Pays-Bas et de la Belgique, volume 58, pages 23–33.
The salts and esters are relatively uncommon, and their uses appear to be limited to chemical research. The sodium salt NaC(COO) can be obtained by oxidation of pentaerythritol C(CHOH) with oxygen in sodium hydroxide solution at pH 10 and about 60 °C, in the presence of palladium as a catalyst.
Japanese Patent 52128317, Sodium methanetetracarboxylate from pentaerythritol
The tetraethyl ester C(COO- CH) is traded as a specialty chemical and has been used in organic synthesis.
Armin de Meijere, Rafael R. Kostikov, Andrei I. Savchenko, Sergei I. Kozhushkov (2004), Diethyl Cyclopropylidenemalonate: Facile Preparation, Generation in situ, and Various Transformations. European Journal of Organic Chemistry, volume 2004 issue 19, Pages 3992–4002.
The anion can be seen as the result of removing four protons from methanetetracarboxylic acid, a hypothetical organic compound with formula CHO or C(COOH). However this acid has not been synthesised (as of 2009), and is believed to be unstable.