Individual Steps of the Mizoroki—Heck Reaction and Intrinsic Reactivity of Intermediate Organopalladium Complexes Studied in the Gas Phase

The mechanism of the Mizoroki-Heck reaction (MHR) was analyzed by collision-induced dissociation (CID) tandem-mass spectrometry and gas-phase ion/molecule reactions (IMRs) as well as by DFT computational analysis. The MHR was performed in the gas phase and the intrinsic reactivity of important intermediates was examined individually. Kinetics and substituent effects of cationic palladiumPCy(3)-aryl complexes (Cy = cyclohexyl) with 2,3-dimethylbutadiene in the MHR were analyzed via IMRs and CID. The kinetics and ion structures of the species involved in the olefin insertion, i.e., the carbopalladation, were investigated. Moreover, linear free-energy correlations-were applied and a concerted mechanism proceeding via a four-membered transition state for the carbopalladation step that exhibited only a minor charge separation was deduced