Structural (XRD) characterization and an analysis of H-bonding motifs in some tetrahydroxidohexaoxidopentaborate(1-) Salts of N-substituted guanidinium cations †
Structural (XRD) characterization and an analysis of H-bonding motifs in some tetrahydroxidohexaoxidopentaborate(1-) Salts of N-substituted guanidinium cations †
The synthesis and characterization of six new substituted guanidium tetrahydroxidohexaoxidopentaborate(1-) salts are reported: [C(NH2)2(NHMe)][B5O6(OH)4]·H2O (1), [C(NH2)2(NH{NH2})][B5O6(OH)4] (2), [C(NH2)2(NMe2)][B5O6(OH)4] (3), [C(NH2)(NMe2)2][B5O6(OH)4] (4), [C(NHMe)(NMe2)2][B5O6(OH)4]·B(OH)3 (5), and [TBDH][B5O6(OH)4] (6) (TBD = 1,5,7-triazabicyclo [4.4.0]dec-5-ene). Compounds 1–6 were prepared as crystalline salts from basic aqueous solution via self-assembly processes from B(OH)3 and the appropriate substituted cation. Compounds 1–6 were characterized by spectroscopic (NMR and IR) and by single-crystal XRD studies. A thermal (TGA) analysis on compounds 1–3 and 6 demonstrated that they thermally decomposed via a multistage process to B2O3 at >650 °C. The low temperature stage (<250 °C) was endothermic and corresponded to a loss of H2O. Reactant stoichiometry, solid-state packing, and H-bonding interactions are all important in assembling these structures. An analysis of H-bonding motifs in known unsubstituted guanidinium salts [C(NH2)3]2[B4O5(OH)4]·2H2O, [C(NH2)3][B5O6(OH)4]·H2O, and [C(NH2)3]3[B9O12(OH)6] and in compounds 1–6 revealed that two important H-bonding R22(8) motifs competed to stabilize the observed structures. The guanidinium cation formed charge-assisted pincer cation–anion H-bonded rings as a major motif in [C(NH2)3]2[B4O5(OH)4]·2H2O and [C(NH2)3]3[B9O12(OH)6], whereas the anion–anion ring motif was dominant in [C(NH2)3][B5O6(OH)4]·H2O and in compounds 1–6. This behaviour was consistent with the stoichiometry of the salt and packing effects also strongly influencing their solid-state structures.
borate, guanidinium salts, H-bonding, oxidoborate, pentaborate(1-), R(8) motifs, tetrahydroxidohexaoxidopentaborate(1-) salts, XRD
Beckett, Michael A.
5b021ef6-fa5c-4f6d-9998-3313558f0dc1
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Rixon, Thomas A.
f5d9498d-b8cc-43b4-9b32-99253e1263db
6 April 2023
Beckett, Michael A.
5b021ef6-fa5c-4f6d-9998-3313558f0dc1
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Rixon, Thomas A.
f5d9498d-b8cc-43b4-9b32-99253e1263db
Beckett, Michael A., Coles, Simon J., Horton, Peter N. and Rixon, Thomas A.
(2023)
Structural (XRD) characterization and an analysis of H-bonding motifs in some tetrahydroxidohexaoxidopentaborate(1-) Salts of N-substituted guanidinium cations †.
Molecules, 28 (7), [3273].
(doi:10.3390/molecules28073273).
Abstract
The synthesis and characterization of six new substituted guanidium tetrahydroxidohexaoxidopentaborate(1-) salts are reported: [C(NH2)2(NHMe)][B5O6(OH)4]·H2O (1), [C(NH2)2(NH{NH2})][B5O6(OH)4] (2), [C(NH2)2(NMe2)][B5O6(OH)4] (3), [C(NH2)(NMe2)2][B5O6(OH)4] (4), [C(NHMe)(NMe2)2][B5O6(OH)4]·B(OH)3 (5), and [TBDH][B5O6(OH)4] (6) (TBD = 1,5,7-triazabicyclo [4.4.0]dec-5-ene). Compounds 1–6 were prepared as crystalline salts from basic aqueous solution via self-assembly processes from B(OH)3 and the appropriate substituted cation. Compounds 1–6 were characterized by spectroscopic (NMR and IR) and by single-crystal XRD studies. A thermal (TGA) analysis on compounds 1–3 and 6 demonstrated that they thermally decomposed via a multistage process to B2O3 at >650 °C. The low temperature stage (<250 °C) was endothermic and corresponded to a loss of H2O. Reactant stoichiometry, solid-state packing, and H-bonding interactions are all important in assembling these structures. An analysis of H-bonding motifs in known unsubstituted guanidinium salts [C(NH2)3]2[B4O5(OH)4]·2H2O, [C(NH2)3][B5O6(OH)4]·H2O, and [C(NH2)3]3[B9O12(OH)6] and in compounds 1–6 revealed that two important H-bonding R22(8) motifs competed to stabilize the observed structures. The guanidinium cation formed charge-assisted pincer cation–anion H-bonded rings as a major motif in [C(NH2)3]2[B4O5(OH)4]·2H2O and [C(NH2)3]3[B9O12(OH)6], whereas the anion–anion ring motif was dominant in [C(NH2)3][B5O6(OH)4]·H2O and in compounds 1–6. This behaviour was consistent with the stoichiometry of the salt and packing effects also strongly influencing their solid-state structures.
Text
molecules-28-03273
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Accepted/In Press date: 5 April 2023
Published date: 6 April 2023
Keywords:
borate, guanidinium salts, H-bonding, oxidoborate, pentaborate(1-), R(8) motifs, tetrahydroxidohexaoxidopentaborate(1-) salts, XRD
Identifiers
Local EPrints ID: 477301
URI: http://eprints.soton.ac.uk/id/eprint/477301
ISSN: 1420-3049
PURE UUID: ce5bbe81-718a-46a6-ab50-c792e6b271a0
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Date deposited: 02 Jun 2023 16:39
Last modified: 17 Mar 2024 02:50
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Author:
Michael A. Beckett
Author:
Peter N. Horton
Author:
Thomas A. Rixon
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