Templated heptaborate and pentaborate salts of cyclo-alkylammonium cations: structural and thermal properties

The synthesis and characterization of a series of cyclo-alkylammonium pentaborate salts {[cyclo-CnH2n-1NR3][B5O6(OH)(4)] (R = H, n = 3, 5-7 (1-4); R = Me, n = 6 (5))} are reported. Compounds 1, 2 and 5 have been further characterized by single-crystal XRD studies. Attempted recrystallization of 3 and 4 yielded small crops of the unexpected heptaborate salts, [cyclo-C6H11NH3](2)[B7O9(OH)(5)]center dot 3H(2)O center dot B(OH)(3) (6) and [cyclo-C7H13NH3](2)[B7O9(OH)(5)]center dot 2H(2)O center dot 2B(OH)(3) (7) which were also characterized crystallographically. All compounds show extensive supramolecular H-bonded anionic lattices templated by the cations. H-bond interactions are described in detail. TGA-DSC analysis of the pentaborates 1-5 showed that they thermally decomposed in air at 800 degrees C to 2.5B(2)O(3), in a 2 step process involving dehydration (<250 degrees C) and oxidative decomposition (250-600 degrees C). BET analysis of materials derived from the pentaborates had internal porosities of <1 m(2) g(-1).