Synthesis and XRD study of an C₂-linked bis(quaternary ammonium) pentaborate: [Me₃NCH₂CH₂NMe₃][B₅O₆(OH)₄]₂

Abstract

The synthesis and characterization of a C2 (ethane) linked bis(trimethylammonium) pentaborate salt, [Me3NCH2CH2NMe3][B5O6(OH)4]2 (1), is reported. Compound 1 has been characterized by 1 H, 11 B, and 13 C NMR Spectroscopy, IR spectroscopy, thermal (TGA/DSC) analysis, and single-crystal X-ray diffraction. There are two independent crystallographic pentaborate(1-) anions in the solid-state structure and these link by H-bonds at -sites into a centrosymmetric tetrameric chain. These chains are crossed-linked by R2 2 (8) H-bond motifs to -sites of neighbouring pentaborate tetrameric units. The [Me3NCH2CH2NMe3] 2+ cations are located between these tetrameric pentaborate(1-) units.

Pentaborate(1-) Salts and a Tetraborate(2-) Salt Derived from C2- or C3-Linked Bis(alkylammonium) Dications: Synthesis, Characterization, and Structural (XRD) Studies

“…Using Etter nomenclature [46] There is some disorder present in the cation and/or cocrystallized molecules all pentaborate(1-) anion structures except 3. Bond lengths and bond angles found for C, N atoms within the organic cations [19,28,37,40,41] are as expected as are the B-O bond lengths, OBO and BOB angles observed for the [B5O6(OH)4] − anion [19,21,28,29,[31][32][33][34][35]; for full details see the Supplementary Information. H-bonding interactions within polyborate salts are extremely common and anion-anion interactions between pentaborate(1-) units, forming giant lattices, are well documented and are signaled as a strong driving force [5,29,34] in templating the crystallization of these anions from the Dynamic Combinatorial Library [42][43][44][45] arising from B(OH)3 under basic conditions [35,36].…”

“…This product rather than the expected product, [Me 3 N(CH 2 ) 3 NMe 3 ][B 5 O 6 (OH) 4 ] 2 was obtained since the [Me 3 N(CH 2 ) 3 NMe 3 ] 2+ cation initially present rapidly undergoes a Hofmann elimination[26,27], with elimination of NMe 3 , under the workup conditions. Repeating the reaction but maintaining the reaction mixture at room temperature during the workup resulted in the high yield (96%) NMe 3 ][B 5 O 6 (OH) 4 ] 2 , has been previously reported by us from the ion exchange method from [Me 3 N(CH 2 ) 2 NMe 3 ]I 2 and B(OH)3 in good (80%) yield[28]. We now report that the related salt, [Me 3 N(CH 2 ) 2 NMe 3 ][B 4 O 5 (OH)4 ] .…”

“…Synthesis, Spectroscopic, Analytical, and Crystallographic Data for Me 3 N(CH 2 ) 2 NMe 3 ]I 2 (1.078 g, 2.7 mmol)[28] was dissolved in H 2 O (20 mL) and stirred with excess (15.0 g) of DOWEX 550A ion-exchange resin (OH − form) for 24 h. The slurry was filtered and B(OH) 3 (0.5 g, 8.1 mmol) was added to the filtrate. The solution was left stand for 4 h and concentrated to ca.…”