N(NPR)(4)[B5O6(OH)(4)](B(OH)(3)](2) AND N(NBU)(4)[B5O6(OH)(4)][B(OH)(3)](2) - CLATHRATES WITH A DIAMONDOID ARRANGEMENT OF HYDROGEN-BONDED PENTABORATE ANIONS

Single-crystal X-ray structure analyses of N(nPr)(4)[B5O6(OH)(4)][B(OH)(3)](2), 1, and N(nBu)(4) [B5O6(OH)(4)][B(OH)(3)](2), 2, reveal that these materials are novel clathrates, the isotypic host structures of which are three-dimensional assemblies of hydrogen-bonded [B5O6(OH)(4)](-) ions and B(OH)(3) molecules. The assembly of only the pentaborate anions is a distorted (i.e., along [102] elongated) four-connected diamond-related network. The N(nPr)(4)(+) and N(nBu)a ions are trapped within the complex three-dimensional channel systems of the host frameworks. Both 1 anti 2 crystallize monoclinically with space group P2(1)/c and Z = 4. The cell constants are: 1: a = 13.592(5), b = 12.082(2), c = 17.355(6) Angstrom, beta = 106.60(2)degrees (298 K); 2: a = 13.874(3), b = 12.585(1), c = 17.588(4) Angstrom, beta = 107.04(1)degrees (238 K). The results obtained by both B-11 and C-13 MAS NMR spectroscopy are discussed. Thermogravimetric studies under a flowing inert-gas atmosphere suggest that water, stemming from polycondensation of the hydrous borate species, is released from the clathrates at ca. 443 K (1) and 398 K (2) before the decomposition of the organic cations starts at ca. 603 K (1) and 603 K (2).