Salt forms of a thioamide : protonation of 1-(2,6-dimethylphenyl)thiourea

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Donnachie, Kristin and Gibson, Bethany and Kennedy, Alan R. and MacCall, Connor and Reid, Marc (2026) Salt forms of a thioamide : protonation of 1-(2,6-dimethylphenyl)thiourea. Acta Crystallographica Section C: Structural Chemistry, 82 (Pt. 3). pp. 129-137. C82. ISSN 2053-2296 (https://doi.org/10.1107/S2053229626001804)

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Abstract

Treating the thioamide 1‐(2,6‐dimethylphenyl)thiourea (C9H12N2S, DMPT) with concentrated aqueous strong acids gave three salt forms with protonation at the thioamide S atom. The structures of 1‐(2,6‐dimethylphenyl)thiouronium chloride, C9H13N2S+·Cl− or [DMPT(H)][Cl], 1‐(2,6‐dimethylphenyl)thiouronium bromide, C9H13N2S+·Br− or [DMPT(H)][Br], and 1‐(2,6‐dimethylphenyl)thiouronium hydrogen sulfate, C9H13N2S+·HSO4− or [DMPT(H)][HSO4], are compared with that of neutral DMPT. Protonation at the S atom results in a systematic lengthening of the C=S bond and a shortening of the C—N bonds, with a larger effect found for the bonds involving the secondary amine rather than the primary amine function. The [DMPT(H)]+ cations are found to adopt one of two possible conformations, with the halide species having secondary N—H syn to S—H, whilst in the hydrogen sulfate structure, this relationship is anti. The change in cation conformation is related to a change in the hydrogen‐bonding motif, but all three salt forms form layered structures with two‐dimensional hydrogen‐bonded units separated by layers of hydrophobic arene rings. An alternative product type was isolated on adding DMPT to concentrated sulfuric or tetrafluoroboric acid. Structures of the dicarbocationic disulfide species (disulfane‐1,2‐diyl)bis[N‐(2,6‐dimethylphenyl)methanediaminium] bis(tetrafluoroborate), C18H24N4S22+·2BF4− or [Dimer][BF4]2, and (disulfane‐1,2‐diyl)bis[N‐(2,6‐dimethylphenyl)methanediaminium] bis(hydrogen sulfate) monohydrate, C18H24N4S22+·2HSO4−·H2O or [Dimer][HSO4]2·H2O, are also described.

ORCID iDs

Donnachie, Kristin, Gibson, Bethany, Kennedy, Alan R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, MacCall, Connor and Reid, Marc ORCID logoORCID: https://orcid.org/0000-0003-4394-3132;
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