469911-15-7Relevant academic research and scientific papers
Stoichiometric and catalytic oxygen activation by trimesityliridium(III)
Jacobi, Bridey Grant,Laitar, David S.,Pu, Lihung,Wargocki, Michael F.,DiPasquale, Antonio G.,Fortner, Kevin C.,Schuck, Stephany M.,Brown, Seth N.
, p. 4815 - 4823 (2002)
Trimesityliridium(III) (mesityl = 2,4,6-trimethylphenyl) reacts with O2 to form oxotrimesityliridium(V), (mes)3Ir=O, in a reaction that is cleanly second order in iridium. In contrast to initial reports by Wilkinson, there is no evidence for substantial accumulation of an intermediate in this reaction. The oxo complex (mes)3Ir=O oxidizes triphenylphosphine to triphenylphosphine oxide in a second-order reaction with ΔH? = 10.04 ± 0.16 kcal/mol and ΔS? = -21.6 ± 0.5 cal/(mol·K) in 1,2-dichloroethane. Triphenylarsine is also oxidized, though over an order of magnitude more slowly. Ir(mes)3 binds PPh3 reversibly (Kassoc = 84 ± 3 M-1 in toluene at 20°C) to form an unsymmetrical, sawhorse-shaped four-coordinate complex, whose temperature-dependent NMR spectra reveal a variety of dynamic processes. Oxygen atom transfer from (mes)3Ir=O and dioxygen activation by (mes)3Ir can be combined to allow catalytic aerobic oxidations of triphenylphosphine at room temperature and atmospheric pressure with overall activity (～60 turnovers/h) comparable to the fastest reported catalysts. A kinetic model that uses the rates measured for dioxygen activation, atom transfer, and phosphine binding describes the observed catalytic behavior well. Oxotrimesityliridium does not react with sulfides, sulfoxides, alcohols, or alkenes, apparently for kinetic reasons.
