RESUMEN
Two substituted phosphonium tetrahydoxidohexaoxidopentaborate(1-) salts, [iPrPPh3][B5O6(OH)4]·3.5H2O (1) and [MePPh3][B5O6(OH)4]·B(OH)3·0.5H2O (2), were prepared by templated self-assembly processes with good yields by crystallization from basic methanolic aqueous solutions primed with B(OH)3 and the appropriate phosphonium cation. Salts 1 and 2 were characterized by spectroscopic (NMR and IR) and thermal (TGA/DSC) analysis. Salts 1 and 2 were thermally decomposed in air at 800 °C to glassy solids via the anhydrous phosphonium polyborates that are formed at lower temperatures (<300 °C). BET analysis of the anhydrous and pyrolysed materials indicated they were non-porous with surface areas of 0.2-2.75 m2/g. Rhe recrystallization of 1 and 2 from aqueous solution afforded crystals suitable for single-crystal XRD analyses. The structure of 1 comprises alternating cationic/anionic layers with the H2O/pentaborate(1-) planes held together by H-bonds. The cationic planes have offset face-to-face (off) and vertex-to-face (vf) aromatic ring interactions with the iPr groups oriented towards the pentaborate(1-)/H2O layers. The anionic lattice in 2 is expanded by the inclusion of B(OH)3 molecules to accommodate the large cations; this results in the formation of a stacked pentaborate(1-)/B(OH)3 structure with channels occupied by the cations. The cations within the channels have vf, ef (edge-to-face), and off phenyl embraces. Both H-bonding and phenyl embrace interactions are important in stabilizing these two solid-state structures.
RESUMEN
The title compound, C(36)H(30)NP(2) (+)·I(-), was obtained accidently from crystallization of a reaction mixture containing [(Ph(3)P)(2)N]OH and B(OH)(3), which was contaminated with MeI. There are two independent [(Ph(3)P)(2)N](+) cations and two I(-) anions within the asymmetric unit. The central PNP angles are non-linear [137.6â (2) and 134.4â (2)°] and the phenyl substituents on P centres adopt different conformations within these two cations.
RESUMEN
The synthesis and characterization of a series of cyclo-alkylammonium pentaborate salts {[cyclo-C(n)H(2n-1)NR(3)][B(5)O(6)(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-C(6)H(11)NH(3)](2)[B(7)O(9)(OH)(5)]·3H(2)O·B(OH)(3) (6) and [cyclo-C(7)H(13)NH(3)](2)[B(7)O(9)(OH)(5)]·2H(2)O·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 °C to 2.5B(2)O(3), in a 2 step process involving dehydration (<250 °C) and oxidative decomposition (250-600 °C). BET analysis of materials derived from the pentaborates had internal porosities of <1 m(2) g(-1).
RESUMEN
The synthesis, structural characterization (XRD), and thermal properties of nine non-metal cation (NMC) pentaborate anion salts, [NMC][B(5)O(6)(OH)(4)] (1a-1i) is described (NMC = [NH(3)CMe(2)(CH(2)OH)](+) (a), [O(CH(2)CH(2))(2)NH(2)](+) (b), [NH(3)CMe(CH(2)OH)(2)](+) (c), [2-(2-CH(2)CH(2)OH)PyH](+) (d), [(CH(2))(4)NH(CH(2)CH(2)OH)](+) (e), [(CH(2))(5)NH(CH(2)CH(2)OH)](+) (f), [2-MeImid](+) (g), [Me(3)NCMe(2)(CH(2)OH)](+) (h), [O(CH(2)CH(2))(2)NMe(2)](+) (i). Single-crystal X-ray diffraction studies on all compounds show that they contain isolated pentaborate anions, H-bonded together in a supramolecular array, with the cations occupying the cavities within the network. Compound 1c was obtained as a partial hydrate (0.16H(2)O). TGA and DSC analysis (in air, 25-1000 degrees C) indicate that compounds 1a-1i thermally decompose via a 2 stage process to B(2)O(3). The first stage (<250 degrees C) is dehydration to condensed polymeric pentaborates {approximate composition: [NMC][B(5)O(8)] (2a-2i)}. Five condensed pentaborates (2a-c, 2e, 2g) were synthesised and characterized by powder XRD and BET analysis. These condensed pentaborates were amorphous. The isolated pentaborates intumesced at approximately 600 degrees C (occupying approximately 10 times their original volume), and then contracted back to black glassy B(2)O(3) solids at 1000 degrees C. The intumescent materials (3a), (3b), (3e), (3g), and a final B(2)O(3) sample (4b) were synthesised and isolated and their porosities determined. BET surface area analysis on the isolated pentaborates (1a-c, 1e, 1g), the condensed pentaborates (2a-c, 2e, 2g), intumesced materials (3a, 3b, 3e, 3g), and B(2)O(3) (4b) showed that they were all 'non-porous' (<1.59 m(2) g(-1)).
RESUMEN
The reaction of metal alkoxides M(OR)4 (M = Ti, Zr; R = organyl) with (MeO)3B3O3 (1 : 0.67) in dry propan-2-one at room temperature led to gels which when dried and calcined in air for 24 h at 500-1000 degrees C afforded bi-phased mixed-oxide materials formulated as 4TiO2 x 3B2O3 and ZrO2 x B2O3 in high ceramic yields and purity; the B2O3 phases of these materials were amorphous. The materials remained amorphous upon calcination at lower temperatures. The TiO2 phase of the 4TiO2 x 3B2O3 was crystalline when calcined at higher temperatures with either anatase (600 degrees C) or rutile (>800 degrees C) being obtained. The ZrO2 phase of the ZrO2 x B2O3 was crystalline when calcined at higher temperatures and was obtained as a metastable tetragonal phase (<700 degrees C) or baddeleylite (>800 degrees C). In a similar reaction, Al(O(i)Pr)3 (2 : 1) gave a bi-phased aluminium borate-boron oxide (Al18B4O(33).7B2O3) after calcination at >700 degrees C. The dried gels and oxide materials were all characterized by elemental analysis, TGA-DSC, and powder XRD.