Gas phase reactions of the negative and positive ions of gold and platinum with aromatic hydrocarbons, thiols and H 2S

Abstract

The negative and positive ions of gold and platinum, Au −, Pt −, Au +, generated by the direct laser ablation of the metals, were reacted with benzene, alkyl substituted benzenes, benzenethiol, H 2S, n-propanethiol and the four butanethiols in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR-MS). Reactions were carried out with ions collisionally cooled, to reduce their kinetic energy and deactivate electronic excited states, and with “hot” ions directly after production by the laser. The negative ions of both metals react at a slower rate than the positive ions and their spectra show fewer products. No products were observed for the reaction of metal negative ions with the aromatic hydrocarbons except for the reaction of Pt − ions with mesitylene to give the (CH 3) 2C 6H 3CH 2 − anion as the major product. The reactions of Au − ions with most of the aryl and the alkyl thiols produced the SR − anion as the major product. The reactions of both Au + and Pt + ions with benzene and the substituted benzenes gave the charge transfer ions L + (e.g. C 6H 6 +) as the major products. Collisionally cooled Pt + ions gave minor product ions identified as Pt-benzyne species (PtC 6H 4 +), while “hot” Pt + ions gave the Pt-benzyne species as the major ions. Benzenethiol reacted with both Au + and Pt + to yield the charge transfer ion C 6H 5SH + as the major product, while the reactions of Au + and Pt + ions with H 2S both gave addition complexes MH 2S + and M(H 2S) 2 +, similar to the reactions of Ag + and Cu +. The reactions of n-propanethiol and the four butanethiols with Au + and Pt + ions generally gave the protonated thiol as the major ion with significant quantities of other ions including addition complexes. These results are different from the previously reported reactions of Cu + and Ag + ions which gave the addition ions as the major products.