Synthesis and characterization of templated pentaborate(1-) salts: X-ray structure of [(2-HOCH2CH2)C4H7NMeH][B5O6(OH)4]·0.3H2O

Charlotte L. Jones, Michael A. Beckett, Simon J. Coles, R. Andrew Davies, Peter N. Horton
2016 Phosphorus Sulfur and Silicon and the Related Elements  
Peer reviewed version Cyswllt i'r cyhoeddiad / Link to publication Dyfyniad o'r fersiwn a gyhoeddwyd / Citation for published version (APA): Jones, C., Beckett, M., Coles, S. J., Davies, R., & Horton, P. N. (2016). Synthesis and characterization of templated pentaborate(1-) salts: X-ray structure of [(2-HOCH2CH2)C4H7NMeH][B5O6(OH)4]·0.3H2O. Phosphorus, Sulfur and Silicon and the Related Elements, 191(4), 628-630. https://doi. Abstract The synthesis of pyrrolidinium pentaborate(1-) and four
more » ... e(1-) and four substituted pyrrolidinium pentaborate(1-) salts from B(OH)3 in aqueous solution are salts are reported. Characterization (IR, NMR, single-crystal XRD) of [(2-HOCH2CH2)C4H7NH2] [B5O6(OH)4]0.3H2O is described in detail. The cation is the largest of the five pyrrolidinium cations studied. A consequence of this is that its solid-state structure has anion-anion interactions () which are different from the other four () structures. There are also stabilizing cation-anion H-bond interactions. Electronic supplementary information (ESI) available. CCDC 1423523. This data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. observed due to the complex borate equilibria observed in aqueous solution. 11,16 The IR spectrum of 1 clearly shows the diagnostic band 16 of pentaborate salts at ~925 cm -1 . X-ray structure of [(2-HOCH2CH2)C4H7NMeH][B5O6(OH)4] The crystallographic data for compound 1 is given in a footnote 17 with full details given in the supplementary data. 18 The ionic salt is comprised of the expected (2-hydroxyethyl)-N-methylpyrrolidinium(1+) cation, partnered with a pentaborate(1-) anion, as shown in Figure 1. The cation was found to be disordered over multiple sites with three significant positions of occupancy identified (4:3:3 ratio) and one of which also included a solvated water molecule. All the disordered versions of the pyrrolidinium ring have an envelope conformation with both substituents equatorial. The bond lengths and internuclear angles observed within the boroxyl (B3O3) rings of the pentaborate anions of 1 are within the ranges observed for previously reported [NMC][B5O6(OH)4] structures. 1,6,15,16 The bond lengths and internuclear angles also lie within the ranges found in related boroxole (B3O3) structures containing both 3-and 4-coordinate B centres bound to O. 19 Electronic supplementary information (ESI) available. CCDC 1423523. This data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. bonds (-21 kJ mol -1 ) are maintained and the H-bond energy for a reciprocal- interaction is the same as that of a C(8) -chain (-16 kJ mol -1 ). 13 The cation in 1 is also 'non-innocent' and cationanion H-bond interactions e.g. N11H11...O4', N11H11...O9', and O11H11B...O8', further stabilize the self-assembled crystal structure. Full details are available in the supplementary information. SUMMARY The synthesis and crystal structures of pyrrolidinium pentaborate(1-) and 4 substituted pyrrolidinium pentaborates are reported. The larger cation present in 1 is unable to fit into the brickwall structure and as a result 1 adopts a similar but different anionic lattice of comparable energy. The solid-state structure of 1 is further stabilized by cation-anion H-bond interactions.
doi:10.1080/10426507.2015.1128921 fatcat:y453bsckprfpbfa3j3jjixpu7i