Di-methyl-ammonium 2,4,5-tri-carb-oxy-benzoate: an example of the deca-rbonylation of N, N-di-methyl-formamide in the presence of a metal and a benzene-polycarb-oxy-lic acid. Is zirconium(IV) the Tsotsi?

Abstract

The title salt, C₂H₈N⁺·C₁₀H₅O₈^-, was the unexpected product of an attempt to prepare a Zr^IV 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 Zr^IV 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.

Keywords: 1,2,4,5-benzene­tetra­carb­oxy­lic acid; Tsotsi; crystal structure; deca­rbonylation; multiple hydrogen bonding.