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

Abstract

Dedicated to Prof. Antonio Togni on the occasion of his 65th birthday and retirement In this article, the synthesis and characterization of new palladium(η 2-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.