Pentaborate(1-) Salts and a Tetraborate(2-) Salt Derived from C 2 - or C 3 -Linked Bis(alkylammonium) Dications: Synthesis, Characterization, and Structural (XRD) Studies.

The synthesis of a number of pentaborate(1-) salts from cations arising from N-substituted alpha,alpha-, alpha,beta-, and alpha,gamma-diaminoalkanes has been attempted in aqueous solution from B(OH)(3) and the appropriate diammine in a 10:1 ratio. Despite relatively mild work-up conditions the pentaborate(1-) salts prepared were not always as anticipated and the following compounds were isolated in good yield: [Me2NH(CH2)(2)NHMe2][B5O6(OH)(4)](2) (1), [Et2NH(CH2)(2)NHEt2][B5O6(OH)(4)](2) (2), [Et2NH2][B5O6(OH)(4)] (3), [Me2NH2][B5O6(OH)(4)] (4), [Me2NH(CH2)(3)NHMe2][B5O6(OH)(4)](2) (5), [Et2NH(CH2)(3)NHEt2][B5O6(OH)(4)](2) (6), [Me3NCH2CH=CH2][B5O6(OH)(4)] (7), and [Me3N(CH2)(3)NMe3] [B5O6(OH)(4)](2)center dot 0.5H(2)O (8). The tetraborate(2-) salt, [Me3N(CH2)(2)NMe3][B4O5(OH)(4)]center dot 2B(OH)(3)center dot 2H(2)O (9) was obtained in moderate yield (41%) from a 3:1 reaction of B(OH)(3) with [Me3N(CH2)(2)NMe3](OH)(2). All compounds were characterized by spectroscopy (H-1, B-11, C-13 NMR and IR) and thermal gravimetric analysis (TGA). BET analysis on materials derived thermally from selected samples (1, 2, 6, 7) all had porosities of < 1 m(2)/g, demonstrating that they were non-porous. Single-crystal XRD structures were obtained for 2, 3, 7, 8 and 9 and all contain extensive H-bonded polyborate lattices.