Polymorphism in (Tricyclohexylphosphine)gold(I) 2-Mercaptobenzoate - A Tale of Two Structural Motifs

(Tricyclohexylphosphine)gold(I) 2-mercaptobenzoate is found in four distinct crystal forms. All forms show a linear P-Au-S geometry. In three of the polymorphs the molecule may be described as spherical, as a result of an intramolecular O-H⋯S bond formed between the carboxylic acid group and the coordinated sulfur atom: i.e., a "ball" motif. These are in contrast to a "rod" otif (previously reported) that features association between centrosymmetric molecules via the familiar carboxylic acid dimer. Both motifs may be obtained under the same crystallizing conditions, a result which indicates that there is little energy difference between the different crystal forms. The process of crystallization may be described as a competition between the efficient crystal packing (ball motif) and the formation of carboxylic acid dimers (rod motif).