PdII Complexes with N‐(Diadamantylphosphanyl)diaminocarbene and Related Ligands: Synthesis and Catalytic Applications in Intermolecular Alkyne Hydroaminations

Abstract

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.