Hydrogen-bonded mol-ecular salts of reduced benzo-thia-zole derivatives with carboxyl-ates: a robust (8) supra-molecular motif (even when disordered)

Abstract

The syntheses and structures of five mol-ecular salts of protonated 4,4,7,7-tetra-methyl-3a,5,6,7a-tetra-hydro-benzo-thia-zol-2-yl-amine (C₁₁H₁₉N₂S⁺) with different deprotonated carb-oxy-lic acids (4-methyl-benzoic acid, 4-bromo-benzoic acid, 3,5-di-nitro-benzoic acid, fumaric acid and succinic acid) are reported, namely 2-amino-4,4,7,7-tetra-methyl-4,5,6,7-tetra-hydro-1,3-benzo-thia-zol-3-ium 4-methyl-benzoate, C₁₁H₁₉N₂S⁺·C₈H₇O₂ ^-, (I), 2-amino-4,4,7,7-tetra-methyl-4,5,6,7-tetra-hydro-1,3-benzo-thia-zol-3-ium 4-bromo-benzoate, C₁₁H₁₉N₂S⁺·C₇H₄BrO₂ ^-, (II), 2-amino-4,4,7,7-tetra-methyl-4,5,6,7-tetra-hydro-1,3-benzo-thia-zol-3-ium 3,5-di-nitro-benzoate, C₁₁H₁₉N₂S⁺·C₇H₃N₂O₆ ^-, (III), bis-(2-amino-4,4,7,7-tetra-methyl-4,5,6,7-tetra-hydro-1,3-benzo-thia-zol-3-ium) fumarate, 2C₁₁H₁₉N₂S⁺·C₄H₂O₄ ^2-,(IV), and the 1:1 co-crystal of bis-(2-amino-4,4,7,7-tetra-methyl-4,5,6,7-tetra-hydro-1,3-benzo-thia-zol-3-ium) succinate and 2-amino-4,4,7,7-tetra-methyl-4,5,6,7-tetra-hydro-1,3-benzo-thia-zol-3-ium hydrogen succin-ate 4,4,7,7-tetra-methyl-3a,5,6,7a-tetra-hydro-benzo-thia-zol-2-yl-amine, 1.5C₁₁H₁₉N₂S⁺·0.5C₄H₄O₄ ^2-·0.5C₄H₅O₄ ^-. 0.5C₁₁H₁₈N₂S, (V). In every case, the cation protonation occurs at the N atom of the thia-zole ring and the six-membered ring adopts a half-chair conformation (in some cases, the deviating methyl-ene groups are disordered over two sets of sites). The C-N bond lengths of the nominal -NH⁺=C-NH₂ fragment of the cation are indistinguishable, indicating a significant contribution of the -NH-C=N⁺H₂ resonance form to the structure. The packing for (I)-(V) features a robust local R ₂ ²(8) loop motif in which the cation forms two near-linear N-H⋯O hydrogen bonds from the N⁺-H group and syn H atom of the amine group to the carboxyl-ate group of an adjacent anion [(V) shows disorder of one of these bonds over N-H⋯O and N⋯H-O contributors but the same R ₂ ²(8) loop results for both disorder components]. The anti H atom of the -NH₂ group also forms an N-H⋯O hydrogen bond, which results in [001] chains in (I) and (II), isolated centrosymmetric tetra-mers in (III) and [100] chains in (IV) and (V). Hirshfeld fingerprint plots and contact percentages for the different types of contacts of the cations are discussed.

Keywords: benzo­thia­zole; crystal structure; hydrogen bond; mol­ecular salt.