Probing Intermediates of Ion/Molecule Reactions by their Independent Gas‐Phase Synthesis and Fragmentation – The Thiomethoxymethyl Complexes [(bipy)M(CH2SCH3)]+ (M=Pt, Pd, Ni)

Abstract

AbstractIn the ion/molecule reaction (IMR) of “rollover”‐cyclometalated [(bipy−H)Pt]+ with (CH3)2S, the loss of C2H4 from the encounter complex was observed as the main process some years ago. The cationic complex [(bipy)Pt(CH2SCH3)]+ was identified as a crucial intermediate by DFT calculations. In order to prove its key role experimentally, the cation has now been generated independently and studied by collision‐induced dissociation (CID). The main process is C2H4 loss, which proves [(bipy)Pt(CH2SCH3)]+ to be an intermediate also in the IMR of [(bipy−H)Pt]+ with (CH3)2S. Based on DFT calculations, the thiomethoxymethyl complexes [(bipy)M(CH2SCH3)]+ (M=Pd and Ni) would also serve as intermediates in the IMRs of [(bipy−H)M]+. While these IMRs cannot be studied explicitly, because the parent ions cannot be generated, the potential intermediate [(bipy)M(CH2SCH3)]+ has been subjected to CID. The main fragmentation channels for both metals corresponds to C2H4 loss. The CID experiments thus provide insights into the hypothetical IMRs of [(bipy−H)M]+ with (CH3)2S. The comparison of the DFT calculations for all three metals Ni, Pd, and Pt with the experimental findings uncovers subtle aspects of the underlying reaction mechanisms. This work highlights the suitability of CID experiments of potential reaction intermediates for the elucidation of reaction mechanisms of IMRs as well as the limitations of this approach.