Intramolecular Hydroamination of Aminoalkenes using Rhodium(i) and Iridium(i) Complexes with N,N- and P,N-Donor Ligands

Cationic rhodium(i) and iridium(i) complexes containing the bidentate heterocyclic N,N-donor ligand bis(1-pyrazolyl)methane (bpm) and the counterion tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF–) were found to be efficient catalysts for the cyclization of activated and unactivated aminoalkenes. The rates of cyclization were found to be highly dependent upon the size and steric bulk of the substituents at the ?-position of the aminoalkene, with large steric bulk leading to faster rates of cyclization. In comparison, analogous rhodium(i) and iridium(i) complexes with the mixed P,N-donor ligand 1-[2-(diphenylphosphino)ethyl]pyrazole (PyP) were found to be less effective as catalysts for this reaction.