title: (13)C, (31)P and (15)N NMR studies of the ligand exchange reactions of auranofin and chloro(triethylphosphine)gold(I) with thiourea.
abstract: The interaction of thiourea (Tu) with auranofin (Et(3)PAuSATg) and its analogue, Et(3)PAuCl has been studied using (13)C, (31)P and (15)N NMR spectroscopy. It is observed that Tu is able to replace both the ligands, Et(3)P and SATg(-) simultaneously from gold(I) in auranofin, forming [Et(3)P-Au-Tu](+) and Tu-Au-SATg complexes. However, no separate resonances for these species were observed either due to their rapid exchange with auranofin and thus giving only the average resonances or because the chemical shifts of either two species are same so that they cannot be resolved. The displaced SATg(-) is oxidized to its disulfide, (SATg)(2). However, some of the displaced Et(3)P is oxidized to Et(3)PO while the remaining reacts with Tu to form Et(3)P-Tu species, characterized by delta 31P of 1.0 ppm, assigned after an independent reaction between Et(3)P and Tu. In an experiment using a 0.05 M solution of auranofin, the Et(3)PO resonance appeared in auranofin spectrum after 4 days of addition of 1.0 equivalent of Tu, showing that the reaction is slow. A resonance for free Et(3)P is also detected in 31P NMR on the addition of CN(-). It is also observed that Tu reacts with Et(3)PAuCl to form [Et(3)P-Au-Tu](+) via displacement of Cl(-), consistent with an upfield shift of 6.2 ppm in >C [double bond] S resonance of Tu in (13)C NMR. In (15)N NMR, a smaller downfield, instead of an upfield shift, in NH(2) resonance of Tu on its addition to auranofin and Et(3)PAuCl indicates that it is not binding to gold(I) through nitrogen.
authors.affiliation: Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
authors.forename: Saeed
authors.initials: S
authors.lastname: Ahmad
authors.forename: Anvarhusein A
authors.initials: AA
authors.lastname: Isab
mesh_terms: D018501:Antirheumatic Agents / Q000737:chemistry* / Q000378:metabolism; D001310:Auranofin / Q000737:chemistry* / Q000378:metabolism; D002247:Carbon Isotopes; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D009587:Nitrogen Isotopes; D050607:Organogold Compounds; D009942:Organometallic Compounds / Q000737:chemistry*; D010759:Phosphorus Isotopes; D013890:Thiourea / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018501:Antirheumatic Agents; D002247:Carbon Isotopes; D008024:Ligands; D009587:Nitrogen Isotopes; D050607:Organogold Compounds; D009942:Organometallic Compounds; D010759:Phosphorus Isotopes; C447642:chloro(triethylphosphine)gold(I); D001310:Auranofin; D013890:Thiourea