Telomerization of amines mediated by cationic N-heterocyclic carbene (NHC) palladium complexes

The synthesis and characterization of novel [(NHC)Pd(allyl)]X complexes (where NHC = N-heterocyclic carbene and X is a counteranion) are reported. The complexes with a general formula [(IPr)Pd(allyl)(S)]X (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, X = BF4 (1) or PF6 (2)) have been structurally characterized by single-crystal diffraction studies and adopt a distorted square-planar geometry and include a coordinated solvent molecule (S). These cationic complexes promote the rapid and selective combination of 1,3-butadiene and amine into telomers. The active complexes are conveniently prepared in situ and display activity even at very low catalyst loadings. Operating temperatures are Mild and can be as low as room temperature. Both secondary and primary amines are cleanly converted to the corresponding telomers.