C-13 and N-15 NMR studies of the interaction of gold(I) captopril with selenocyanate, selenourea, and thiourea in aqueous solution

The interaction of (KSeCN)-C-13-N-15 with gold(I)-captopril (Aucap)(n) in aqueous solution was studied by C-13 and N-15 NMR spectroscopy. The (SeCN-)-C-13-N-15 interacts with (Aucap)(n) to form an unstable [cap-Au-(SeCN)-C-13-N-15](-) species which readily undergoes disproportionation and redox reactions to generate [Au((CN)-C-13-N-15)(2)](-), (cap)(2), Se-0, and Au-0. The approximate second-order rate constant of disproportionation of [cap-Au-(SeCN)-C-13-N-15](-) is found to be 0.014 +/- 0.001 1 mol(-1) h(-1). The C-13 and N-15 chemical shifts and (1)J(Se-77- C-13) and (1)J(C-13- N-15) coupling constants for free (SeCN-)-C-13-N-15 and [Au((CN)-C-13-N-15)(2)](-) species are reported. The interaction of selenourea (SeU) with (Aucap)(n) resulted in the formation of a [cap-Au-SeU] complex which underwent decomposition and redox reactions to produce (cap)(2), Se-0, and Au-0 species. Thiourea gave rise to a stable [cap-Au-TU] complex which did not undergo redox reaction. (C) 1997 Elsevier Science Inc.