Electronic and steric control over Au⋯Au, C–H⋯O and C–H⋯π interactions in the crystal structures of mononuclear triarylphosphinegold(i) carbonimidothioates: R3PAu[SC(OMe)=NR′] for R = Ph, o-tol, m-tol or p-tol, and R′ = Ph, o-tol, m-tol, p-tol or C6H4NO2-4

Abstract

The structures of R₃PAu[SC(OMe)=NR′], for R = Ph, o-tol, m-tol or p-tol, and R′ = Ph, o-tol, m-tol, p-tol or C₆H₄NO₂-4, feature linear P-Au-S coordination geometries with intramolecular Au⋯O or Au⋯π interactions depending on the substitution patterns of the R and/or R′ groups. For R = Ph, intramolecular Au⋯O interactions are observed exclusively but when R = p-tol, intramolecular Au⋯π interactions are found unless precluded by steric crowding, i.e. in the case when R′ = m-tol, or by electronic reasons such as the presence of an electron withdrawing nitro group, i.e. when R′ = C₆H₄NO₂-4. In the latter case, aurophilic interactions (Au⋯Au = 3.0872(4) Å) are formed, uniquely amongst the series. The mode of coordination of the thiolate ligands in these complexes, arising from either steric or electronic factors or both, has a profound influence on the supramolecular aggregation patterns operating in their crystal structures. In the solvent-free systems that feature intramolecular Au⋯O interactions, columns of molecules stack so that the thiolate residues interdigitate to a greater or lesser extent leaving the aryl groups of the phosphine ligands facing each other, forming phenyl embraces in the Ph₃P species or being connected by C–H⋯π contacts involving methyl-H atoms in the isomeric tolyl₃P structures. In structures featuring intramolecular Au⋯π interactions, the methoxy-O atom is more accessible for the formation of C–H⋯O contacts. Finally, in the cases where the nitro substituent is present, at least one of the nitro-O atoms is involved in C–H⋯O intercations. In summary, subtle changes in electronic character and/or steric profile of the phosphine and thiolate ligands are seen to influence, systematically, the crystal packing.