Preparation of Imidazol‐2‐ylidene Carbene Palladacycles with Bi‐ and Tridentate Schiff Bases – Analyses of the Spectroscopic, Molecular Structure, and DFT Calculation Data

The treatment of appropriate benzylideneimine palladacycles with potentially polydentate imidazol-2-ylidene silver carbene complexes produced new palladium organometallics with the N-heterocyclic carbene (NHC) coordinated to the palladium center. The NHCs bearing two carbene moieties show a bridging coordination mode across the two metal atoms and may also display a simultaneous bridging/chelating behavior. DFT calculations were performed for the compounds for which the typical fluxional behavior of hemilabile carbenes was observed upon close inspection of the 1H NMR spectra. The crystal and molecular structure of 13 was determined by X-ray crystallography and contrasted against the computational data for 14 to determine the most favorable disposition of the fluxional equilibrium of the latter.