Hydrogen-bonded molecular salts of reduced benzothiazole derivatives with carboxylates: A robust (8) supramolecular motif (even when disordered)

Abstract

The syntheses and structures of five molecular salts of protonated 4,4,7,7-tetramethyl-3a,5,6,7a-tetrahydrobenzothiazol-2-ylamine (C 11 H 19 N 2 S +) with different deprotonated carboxylic acids (4-methylbenzoic acid, 4-bromobenzoic acid, 3,5-dinitrobenzoic acid, fumaric acid and succinic acid) are reported, namely 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 4-methylbenzoate, C 11 H 19 N 2 S + ·C 8 H 7 O 2 -, (I), 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 4-bromobenzoate, C 11 H 19 N 2 S + ·C 7 H 4 BrO 2 -, (II), 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 3,5-dinitrobenzoate, C 11 H 19 N 2 S + ·C 7 H 3 N 2 O 6 -, (III), bis(2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium) fumarate, 2C 11 H 19 N 2 S + ·C 4 H 2 O 4 2-,(IV), and the 1:1 co-crystal of bis(2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium) succinate and 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium hydrogen succinate 4,4,7,7-tetramethyl-3a,5,6,7a-tetrahydrobenzothiazol-2-ylamine, 1.5C 11 H 19 N 2 S + ·0.5C 4 H 4 O 4 2- ·0.5C 4 H 5 O 4 -. 0.5C 11 H 18 N 2 S, (V). In every case, the cation protonation occurs at the N atom of the thiazole ring and the six-membered ring adopts a half-chair conformation (in some cases, the deviating methylene groups are disordered over two sets of sites). The C - N bond lengths of the nominal -NH + =C - NH 2 fragment of the cation are indistinguishable, indicating a significant contribution of the -NH - C=N + H 2 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 carboxylate 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 -NH 2 group also forms an N - H⋯O hydrogen bond, which results in [001] chains in (I) and (II), isolated centrosymmetric tetramers 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.