PdIIComplexes with N-(Diadamantylphosphanyl)diaminocarbene and Related Ligands: Synthesis and Catalytic Applications in Intermolecular Alkyne Hydroaminations

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 (diisopropyl-amino)(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 Pd-II 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