Palladium(II) Complexes with N-Phosphine Oxide-Substituted Imidazolylidenes (PoxIms): Coordination Chemistry and Catalysis

The coordination chemistry of N-phosphine oxide-substituted imidazolylidenes (PoxIms) as heteroditopic, hemilabile ligands toward palladium(II) has been investigated. Both bis-carbene and mono-carbene complexes can be prepared, but the latter are accessible only in the presence of ancillary ligands that do not easily dissociate from the metal center. The phosphanyl oxide group was found to often coordinate to palladium(II) as well, though this interaction appears to be weak as this group is indeed easily replaced by, e.g., a solvent molecule. The resulting complexes have been tested as catalysts in the low-temperature Suzuki reaction of 4-chloroanisole with phenylboronic acid and they show promise for further optimization studies.