X-Ray crystallographic and extended X-ray absorption fine structure studies of gold(I) complexes containing weak intermolecular interactions

Abstract

The crystal and molecular structures of [Au₂{S₂CN(C₂H₄OMe)₂}₂], [Au(PPh₃)(SCH₂CO₂H)], [Au(PPh₃)(SCMe₂CO₂H)] and [Au(PPh₃)(SCH₂CO₂Me)] have been determined. All compounds contain an approximately linear primary co-ordination sphere of ligands about the gold atom, but they differ markedly in their type of intermolecular interaction. In [Au₂{S₂CN(C₂H₄OMe)₂}₂] the supramolecular array is dominated by an almost linear, polymeric backbone of gold atoms with alternate gold–gold contacts of 2.7902(6) (intramolecular) and 3.1572(7) Å (intermolecular), whereas in [Au(PPh₃)(SCH₂CO₂H)] dimers associated through long gold–sulfur contacts of 3.131(2) Å are held together in a polymeric chain by hydrogen bonding between neighbouring carboxylic acid residues. The increased steric bulk of the thiolate ligand in [Au(PPh₃)(SCMe₂CO₂H)] caused by the methyl groups on the α-carbon atom precludes association of the gold centres, but hydrogen bonding between carboxylates as in the SCH₂CO₂H compound causes dimerisation. Compound [Au(PPh₃)(SCH₂CO₂Me)] exists as a monomer with no evidence of weak intermolecular interactions. Analysis of ambient-temperature EXAFS (extended X-ray absorption fine structure) measurements on solid samples of the first two compounds yield gold–gold separations of 2.775(2) and 3.271(6) Å and 4.188(15) Å, respectively. Gold–sulfur separations of 2.290(1) and 3.532(8) and of 2.329(4) and 3.124(19) Å, respectively, are also in good agreement with X-ray data.