Fast atom bombardment mass spectrometry of ionic gold(I) and gold(III) carbene derivatives: An investigation of the formation of [M - H]+ species

Fast atom bombardment (FAB) mass spectrometry of the gold(I) and gold(III) derivatives, {Au[C(Y)–NHAr]2}+X− and {Au[C(Y)–NHAr]2I2} + X− (Y =OC2H5 or NHAr; X− = CIO4− or BF4−; Ar = p‐CH3C6H4) has led to the detection, for the alkoxyamino derivatives only, of [M–H]+˙ molecular species. The mechanism of the formation of these unusual species has been studied with respect to the oxidation state of gold, nature of the matrix, matrix acidity and ligand structure. The energetics of two possible alternative mechanisms has been studied by means of ab initio theoretical calculations. Both experimental and theoretical data indicate that [M–H]+˙ formation is due to the reaction of M+ with H+‐philic and/or H˙‐philic species produced from the matrix by FAB. Whatever the operative mechanism, the [M–H]+˙ formation is to be considered a FAB‐induced oxidative process.