Département de chimie moléculaire

We have recently reported a detailed ESI-collision activated reaction/collision activated reaction (ESI-CAR/CAR) and ESI-collision activated reaction/collision induced dissocn. (ESI-CAR/CID) mass spectrometric investigation, combined with quantum chem. calcns., to elucidate the reaction mechanism of [2 + 1] cycloaddn. between alkyne and norbornadiene using a Pd(II) complex as catalyst. The coordination mode of alkyne on the metal was shown to be an essential preliminary step of the reaction, but mass spectrometric results were difficult to rationalize according to changes in the exptl. conditions. In this work we present a detailed RRKM modeling of these expts. using MassKinetics software. We demonstrate how essential kinetic modeling is in order to interpret these expts.: both for phenomenol. aspects (understand spectra and changes in their pattern due to energetic modifications) and as a link between quantum chem. results and tandem MS expts. Complete energy profile for isomerization and decompn. processes of [Pd[(t-Bu)(Ph)PO]₂H + PhCCH]⁺ complexes has been detd. through kinetic modeling of exptl. data. Detailed modeling procedure is presented; approxns. discussed and validated for quant. comparison with quantum chem. calcns. Agreement between isomerization barriers detd. with kinetic modeling of exptl. data and those detd. through quantum chem. was found to be within few kcal/mol supporting the validity of the approach and assumptions made in the model.