Di­methyl­ammonium 2,4,5-tri­carb­oxy­benzoate: an example of the deca­rbonylation of N,N-di­methyl­formamide in the presence of a metal and a benzene­polycarb­oxy­lic acid. Is zirconium(IV) the Tsotsi?

The title salt, C(2)H(8)N(+)·C(10)H(5)O(8) (−), was the unexpected product of an attempt to prepare a Zr(IV) metal–organic framework with benzene-1,2,4,5-tetra­carb­oxy­lic acid (1,2,4,5-H(3)B4C). In the reaction, the DMF solvent has been decarb­on­yl­ated, forming the di­methyl­ammonium cation, with one proton lost from the tetra­carb­oxy­lic acid. It is proposed that the Zr(IV) salt acts as a Tsotsi or robber, plundering CO from the DMF mol­ecule. The resulting salt crystallizes with two cations and two anions in the asymmetric unit. An intra­molecular hydrogen bond forms between a carb­oxy­lic acid substituent and the carboxyl­ate group of each of the monodeprotonated (1,2,4,5-H(3)B4C(−)) anions. In the crystal, an extensive array of O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds generates a three-dimensional network, with columns of cations and anions forming along the b axis.