X-RAY CRYSTALLOGRAPHIC AND EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE STUDIES OF GOLD(I) COMPLEXES CONTAINING WEAK INTERMOLECULAR INTERACTIONS

The crystal and molecular structures of [Au-2{S2CN(C2H4OMe)(2)}(2)], [ Au(PPh3)(SCH2CO2H)], [Au(PPh3)(SCMe2CO2H)] and [Au(PPh3)(SCH2CO2Me)] h ave been determined. All compounds contain an approximately linear pri mary co-ordination sphere of ligands about the gold atom, but they dif fer markedly in their type of intermolecular interaction. In [Au-2{S,C N(C2H4OMe)(2)}(2)] the supramolecular array is dominated by an almost linear, polymeric backbone of gold atoms with alternate gold-gold cont acts of 2.7902(6) (intramolecular) and 3.1572(7) Angstrom (intermolecu lar), whereas in [Au(PPh3)(SCH2CO2H)] dimers associated through long g old-sulfur contacts of 3.131(2) Angstrom are held together in a polyme ric chain by hydrogen bonding between neighbouring carboxylic acid res idues. The increased steric bulk of the thiolate ligand in [Au(PPh3)(S CMe2CO2H)] caused by the methyl groups on the alpha-carbon atom preclu des association of the gold centres, but hydrogen bonding between carb oxylates as in the SCH2CO2H compound causes dimerisation. Compound [Au (PPh3)(SCH2CO2Me)] exists as a monomer with no evidence of weak interm olecular 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) Angstrom and 4.188(15) Angstrom, respectively. Gold-sulfur separat ions of 2.290(1) and 3.532(8) and of 2.329(4) and 3.124(19) Angstrom, respectively, are also in good agreement with X-ray data.