Tetrahydroxidohexaoxidopentaborate(1-) Salts of C<sub>6</sub>-Linked Substituted Diimidazolium and Dipyrrolidinium Cations: Synthesis, Characterization and XRD Studies

oleh: Ahmad R. Al-Dulayymi, Michael A. Beckett, Radek Braganca, Simon J. Coles, Peter N. Horton, Thomas A. Rixon

Format: Article
Diterbitkan: MDPI AG 2024-08-01

Deskripsi

Several tetrahydroxidohexaoxidopentaborate(1-) salts of <i>N</i>-substituted diimidazolium cations or <i>N</i>-substituted dipyrrolidinium cations linked through <i>N</i>-C<sub>6</sub>-<i>N</i> chains have been synthesized and characterized spectroscopically (NMR, IR) and by single-crystal XRD studies: [R(NC<sub>3</sub>H<sub>3</sub>N)(CH<sub>2</sub>)<sub>6</sub>(NC<sub>3</sub>H<sub>3</sub>N)R][B<sub>5</sub>O<sub>6</sub>(OH)<sub>4</sub>]<sub>2</sub>·xH<sub>2</sub>O (R = Me, x = 0 (<b>1</b>); R = Et, x = 3 (<b>2</b>); [Me(NC<sub>3</sub>H<sub>3</sub>N)(CH<sub>2</sub>(C<sub>6</sub>H<sub>4</sub>)CH<sub>2</sub>)(NC<sub>3</sub>H<sub>3</sub>N)Me][B<sub>5</sub>O<sub>6</sub>(OH)<sub>4</sub>]<sub>2</sub> (<b>3</b>), [(C<sub>4</sub>H<sub>8</sub>N)(R)(CH<sub>2</sub>)<sub>6</sub>(R)(NC<sub>4</sub>H<sub>8</sub>)][B<sub>5</sub>O<sub>6</sub>(OH)<sub>4</sub>]<sub>2</sub>·xB(OH)<sub>3</sub> (R = Me, x = 0 (<b>4</b>, two polymorphs); R = Et, x = 0 (<b>5</b>); R = Bu, x = 4 (<b>6</b>); R = allyl, x = 0 (<b>7</b>)). Representative samples (<b>1</b> and <b>7</b>) were also characterized by thermal (TGA/DSC) studies; compounds are thermally decomposed to B<sub>2</sub>O<sub>3</sub> in air. Numerous anion-anion H-bonding interactions are present in the solid-state structures of <b>1</b>–<b>5</b> and <b>7</b> as giant anionic networks. Unusually, in <b>6</b> there are no R<sub>2</sub><sup>2</sup>(8) anion-anion interactions as the co-crystallized B(OH)<sub>3</sub> bridges between all pentaborate anions. H-bonding interactions in <b>1</b>–<b>7</b> have been examined using Etter graph set analysis; C(8), C<sub>3</sub><sup>3</sup>(18), R<sub>2</sub><sup>2</sup>(8), R<sub>2</sub><sup>2</sup>(12) and R<sub>4</sub><sup>4</sup>(12) motifs have been identified.