Proton-linked bi- and tri-metallic gold cyanide complexes observed by ESI-MS spectrometry.

Electrospray ionization spectra of potential cyanide-containing gold-drug metabolites revealed additional, weak, unanticipated peaks at approximately twice the mass of the gold(I) and gold(III) cyanide complexes. The exact masses correspond to proton-linked bimetallic complexes, [H[Au(CN)(m)](2)](-), (m=2,4). Further investigation revealed a total of 12 examples, including trimetallic complexes, [H(2)[Au(CN)(m)](3)](-); mixed species with two complexes, [H[Au(CN)(2)][Au(CN)(4)]](-); and thiolato species, [H[(RS)Au(CN)(3)](2)](-). trans-[AuX(2)(CN)(2)Cl(2)](-) and trans-[AuX(2)(CN)(2)Br(2)](-) generated (35)Cl/(37)Cl and (79)Br/(81)Br isotopic patterns for the protonated bi- and tri-metallic analogues which were in good agreement with the presence of four or six halide ligands, respectively. Concentration-dependent studies demonstrated that the signals are independent of the solution concentrations of mono-metallic precursors, suggesting formation in the gas phase during or following droplet desolvation.