The catalytic potential of palladium(II) complexes with chelating N -phosphanyl- N -heterocyclic carbenes featuring a saturated imidazolin-2-ylidene or tetrahydropyrimid-2-ylidene ring has been investigated in intermolecular alkyne hydroamination reactions. The complexes were found to be among the most active Pd-based catalysts for these processes and to enable the use of low reaction temperatures (40 °C) and of solventless conditions. The Pd complexes require activation by 2 equiv of a silver salt to remove chlorido ligands from the metal coordination sphere; they can however also be presynthesized in active form, which allows their use under silver-free conditions. The hydroamination reaction was found to efficiently proceed with terminal alkynes and different ring-substituted, primary arylamine substrates.

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.

A new N‐diadamantylphosphanyldiaminocarbene 5 is prepared, isolated, and characterized. The carbene appears to be much more stable than previously reported di‐tert‐butyl congeners. The molecular structure of the carbene is determined by X‐ray diffraction analysis. A new (diisopropylamino)(diadamantylphosphanyl)carbene 8 is also prepared in situ, but not isolated, since in this case, the adamantyl groups do not render the carbene more stable, with respect to previously known carbenes with di‐tert‐butyl substitution. Carbene 8 reacts in situ with phenylazide to give iminophosphane 9, which is also accessible from carbene 5 upon rearrangement under heating. Stable chelate PdII complexes are synthesized using both carbene 5 and iminophosphane 9 as ligands. The complex with ligand 9 displays very promising catalytic performance in the intermolecular hydroamination of alkynes with primary arylamines.