Monitoring of Reaction Intermediates in the Gas Phase: Ruthenium‑Catalyzed C–C Coupling

Investigation of catalytic organometallic reactions often relies on mass spectrometry. Frequently, however, possible reaction intermediates along the catalytic cycle correspond to the same mass-to-charge ratio and have rather similar molecular composition. We have shown for the C–C coupling between phenylacetylene and pyridine catalyzed by the ruthenium complex [RuCp­(PPh3)­(Py)2]+ that using a combination of collision-induced dissociation experiments, infrared multiphoton dissociation spectroscopy, bimolecular reactions, and DFT calculations it is possible to study isobaric complexes and characterize the key intermediates in the reaction cycle. In addition, a so far elusive ruthenium complex with π-coordinated alkyne molecule has been spectroscopically characterized.