Tetrabutylammonium hydrogen bisbenzoate: crystal structure and study of short hydrogen bonds in hydrogen bisbenzoate anion system

Abstract

Tetrabutylammonium hydrogen bisbenzoate (bioxyanion) is a useful nucleophile, soluble in organic solvents and capable of catalysing the silylketene acetal initiated group transfer polymerisation of alkylacrylate monomers, as well as a carbonate interchange reaction of aromatic biphenols with diphenyl carbonate. Tetrabutylammonium hydrogen bisbenzoate has been characterised by ¹H and ¹³C NMR as well as FTIR spectroscopy and compared with its acid and corresponding salts. The structure of [N(Bu)₄]⁺[(PhCOO)₂H]^– was determined by single crystal X-ray diffraction. Crystals of C₃₀H₄₇NO₄ are orthorhombic, space group P_ccn with a= 13.038(1), b= 13.589(1), c= 17.124(3)Å and Z= 4. Half of each cation and anion is related to the other half by a two fold axis parallel to the c axis and nitrogen atoms as well as hydrogen atoms of the O ⋯ H ⋯ O group being placed on the two-fold axis. Two benzoate residues in the anion are linked through a short crystallographically symmetrical O ⋯ H ⋯ O hydrogen bond with O ⋯ O distance of 2.459(3)Å. Bifurcated C–H ⋯ O hydrogen bonds from oxygen of the carbonyls connect the cations and anions to form infinite chain networks in the crystal.