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+center dot C10H5O8-, 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-H3B4C). 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-H3B4C-) anions. In the crystal, an extensive array of O-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds generates a three-dimensional network, with columns of cations and anions forming along the b axis.