Collect. Czech. Chem. Commun. 2010, 75, 971-980
Published online 2010-09-22 08:35:17

Synthesis, characterization, and thermal properties of benzylammonium pentaborate [C6H5CH2NH3][B5O6(OH)4]

Michael A. Becketta,*, Peter N. Hortonb, Michael B. Hursthouseb, James L. Timmisa and K. Sukumar Varmac

a School of Chemistry, Bangor University, Bangor, LL57 2UW, UK
b School of Chemistry, Southampton University, Southampton, SO16 1BJ, UK
c Pilkington Building Products R and D, European Technical Centre, Lathom, Lancashire, L40 3UF, UK


[C6H5CH2NH3][B5O6(OH)4] was obtained as colourless crystals in high yield from a MeOH/ H2O (1:1) solution of benzylamine and boric acid (1:5). A single-crystal X-ray study confirmed that the solid-state structure was comprised of a supramolecular H-bonded pentaborate anion lattice, templated by the benzylammonium cations which occupy positions within the lattice cavities. Each pentaborate anion formed 4 H-bonds to 4 neighbouring pentaborate anions at α,α,α,β acceptor sites. Additionally, each cation H-bonds to 3 pentaborate anions. Crystals were monoclinic, P21/c, with a = 9.3511(2) Å, b = 14.5157(4) Å, c = 10.4670(2) Å, β = 90.778(2)°, T = 120 K, V = 1420.64(6) Å3, and Z = 4. TGA/DSC analysis showed that [C6H5CH2NH3][B5O6(OH)4] thermally decomposed in air at 800 °C to 2.5B2O3, via a low-temperature (200–250 °C) dehydration step to a condensed pentaborate.

Keywords: Benzylammonium; Pentaborate; Supramolecular; Thermal decomposition; Hydrogen bonding.

References: 38 live references.