Synthesis, structural characterization and in vitro anticancer screening of several gold(I) thiolate, dithiocarbonate and dithiocarbamate complexes

The crystal and molecular structures of four (triphenylphosphine)-gold(I) complexes synthesized from chloro (triphenylphosphine)-gold(I) and the thiols 5-methyl-1,3,4-oxadiazole-2-thiol and 5-methyl-1,3,4-thiadiazole-2-thiol, the dithiocarbonate potassium O-isopropyldithiocarbonate and the dithiocarbamate sodium dibenzyl-dithiocarbamate have been determined. (5-methyl-1,3,4-oxadiazole-2-thiolato)-triphenylphosphine-gold(I) (1), (5-methyl-1,3,4-thiadiazole-2-thiolato)-triphenylphosphine-gold(I) (2), (O-isopropyldithiocarbonato-S)-triphe-nylphosphine-gold(I) (3) and (N,N-dibenzyldithiocarbamato-S)-triphenylphosphine-gold(I) (4) all exhibit a nearly linear two-coordinate gold(I) metal center. The structures of the two thiolate complexes contain similar Au-S-C angles of 100.86(10)& DEG; in (1) and 99.51(13)& DEG; in (2), but different Au-S-C-O/S torsional angles of 36.9(3)& DEG; and-15.0(3)& DEG;, respectively, highlighting a 3.227(2) & ANGS; intramolecular gold-oxygen contact in (1) and a 3.2635(11) & ANGS; intramolecular gold-sulfur contact in (2), the Au???S distance being less than the sum of the Van der Waals radii. The packing in (1) features a 4.234(1) & ANGS; intermolecular Au???S contact while (2) features a very long 4.8408(3) & ANGS; gold-gold contact. In the structure of the dithiocarbonate (3) the Au-S-C bond angle of 102.49(14)& DEG; is meaningfully larger than the corresponding angle in the structure of the dithiocarbamate (4), with an Au-S-C angle of 98.0(2)& DEG;, highlighting an even shorter intramolecular gold-sulfur contact in (4) of 3.0120 (18) & ANGS; which is significantly less than the sum of the Van der Waals radii. The structure of (4) is accompanied by nearly planar Au-S-C-S torsional angle of-3.6(4) and no intramolecular Au???S or Au???Au contacts, while in the dithiocarbonate (3) the Au-S-C-S torsional angle of 175.1(3) reveals the absence of an intra-molecular gold-sulfur contact, instead featuring an intramolecular gold-oxygen interaction. Each product was characterized through X-ray crystallography, 1H, 13C and 31P NMR, elemental analysis, IR and MS. In collabo-ration with the National Institutes of Health (NIH) Developmental Therapeutics Programs (DTP), the complexes have been evaluated for cytotoxic activity against the National Cancer Institute 60 human tumor cell lines screen (NCI-60). The complexes exhibited mild cytotoxicity similar to other known gold(I) phosphine and thiolate complexes.