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, C2H8N+·C10H5O8-, was the unexpected product of an attempt to prepare a ZrIV metal-organic framework with benzene-1,2,4,5-tetra-carb-oxy-lic acid (1,2,4,5-H3B4C). In the reaction, the DMF solvent has been decarb-on-yl-ated, forming the di-methyl-ammonium cation, with one proton lost from the tetra-carb-oxy-lic acid. It is proposed that the ZrIV salt acts as a Tsotsi or robber, plundering CO from the DMF mol-ecule. The resulting salt crystallizes with two cations and two anions in the asymmetric unit. An intra-molecular hydrogen bond forms between a carb-oxy-lic acid substituent and the carboxyl-ate group of each of the monodeprotonated (1,2,4,5-H3B4C-) 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.