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Chiral anionic layers in tartramide spiroborate salts and variable solvation for [N R 4 ][B(TarNH 2 ) 2 ] ( R = Et, Pr or Bu)
Author(s) -
Soecipto Aristyo,
Wong Lawrence W.-Y.,
Sung Herman H.-Y.,
Williams Ian D.
Publication year - 2020
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229620008384
Subject(s) - solvation , variable (mathematics) , chemistry , physics , crystallography , thermodynamics , combinatorics , stereochemistry , mathematics , ion , organic chemistry , mathematical analysis
The spiroborate anion, namely, 2,3,7,8‐tetracarboxamido‐1,4,6,9‐tetraoxa‐5λ 4 ‐boraspiro[4.4]nonane, [B(TarNH 2 ) 2 ] − , derived from the diol l ‐tartramide TarNH 2 , [CH(O)(CONH 2 )] 2 , shows a novel self‐assembly into two‐dimensional (2D) layer structures in its salts with alkylammonium cations, [N R 4 ] + ( R = Et, Pr and Bu), and sparteinium, [HSpa] + , in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, C 12 H 28 N + ·C 8 H 12 BN 4 O 8 − , the tetraethylazanium salt hydrate, C 8 H 20 N + ·C 8 H 12 BN 4 O 8 − ·6.375H 2 O, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, C 16 H 36 N + ·C 8 H 12 BN 4 O 8 − ·C 2 H 5 OH·0.5H 2 O, and the sparteinium (7‐aza‐15‐azoniatetracyclo[7.7.1.0 2,7 .0 10,15 ]heptadecane) salt as the ethanol monosolvate, C 15 H 27 N 2 + ·C 8 H 12 BN 4 O 8 − ·C 2 H 5 OH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt 4 ] salt is highly hydrated with around 6.5H 2 O per cation, the [NPr 4 ] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu 4 ] salt is intermediate and has EtOH and H 2 O in its cation layer, which is similar to the arrangement for the chiral [HSpa] + cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.