MECHANISTIC FEATURES OF IRIDIUM PINCER COMPLEX-CATALYZED HYDROCARBON DEHYDROGENATION REACTIONS - INHIBITION UPON FORMATION OF A MU-DINITROGEN COMPLEX

Deuterium-labeling studies show that vinyl C-H oxidative addition of t ert-butylethylene (tbe) to IrH2{C6H3-2,6-(CH2PBu2t)(2)} (1) is rapid a nd reversible, while the stoichiometric hydrogenation of tbe by I is s lower and irreversible. The dinitrogen complex, [Ir{C6H3-2,6-(CH2PBu2t )(2)}](2)(mu L-N-2) (3), results from the reaction of 1 with excess tb e under 1 atm of nitrogen. A single-crystal X-ray structure determinat ion of 3 reveals a perpendicular arrangement of the P-C-P pincer ligan ds, which accounts for the surprising stability of 3 and the inhibitin g effect of nitrogen on reactions catalyzed by 1.