Continuous monitoring using electrospray ionisation mass spectrometry (ESI-MS) shows that Wilkinson's catalyst hydrogenates a charge-tagged alkyne to the corresponding alkene, and at only a marginally slower rate, to the alkane. No rhodium-containing intermediates were observed during the reaction, consistent with the established mechanism which points at the initial dissociation of triphenylphosphine from Rh (PPh 3) 3 Cl as being the key step ...
