Measuring the Olefin-to-Pd(0) Bond Strength: A Kinetic Study Involving Olefin Exchange Reactions on Palladium(0) Complexes Bearing Isocyanide Ligands

In this article, the synthesis and characterization of new palladium(η2-olefin) complexes bearing isocyanides as spectator ligands are described. These derivatives have been tested on olefin exchange reactions, allowing to define a scale of strength of the palladium(0)-olefin bond. In this way we have proved that dimethyl fumarate can be released by the metal center much more easily than the other olefins and that (Z)-1,2-ditosylethene is by far the most firmly anchored to palladium. When the sterically encumbered tetramethylethene-1,1,2,2-tetracarboxylate (tmetc) is involved in the olefin exchange, the reaction kinetics can be monitored by UV-Vis spectrophotometry, showing that the process follows a second-order rate law. This response indicates that the reaction mechanism is associative, as is also confirmed by a DFT study.