Iridium and rhodium “PNP” aminodiphosphine complexes used as catalysts in the oxidation of styrene

Abstract

Six PNP or aminodiphosphine ligands were synthesized and complexed to the transition metals iridium and rhodium to give [(η⁵-C₅Me₅)MCl{η²-P,P′-(PPh₂)₂NR}]PF₆, where M = Ir (1) and Rh (2) and R = cyclohexyl (a), iso-propyl (b), pentyl (c), phenyl (d), chlorophenyl (e) and methoxyphenyl (f). These complexes were fully characterized by NMR, elemental analyses and IR spectroscopy. Crystals of 1f and 2f were obtained, which showed a distorted octahedral geometry around the metal centers. These complexes showed good activity in the oxidation of styrene using tert-butyl hydroperoxide (TBHP) as the oxidant. The iridium complexes were more active than the rhodium complexes. Higher yields for benzaldehyde were achieved in comparison to styrene oxide for all catalysts.