Mechanistic Features of Iridium Pincer Complex Catalyzed Hydrocarbon Dehydrogenation Reactions: Inhibition upon Formation of a μ-Dinitrogen Complex

Deuterium-labeling studies show that vinyl C−H oxidative addition of tert -butylethylene (tbe) to IrH 2 {C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 1 ) is rapid and reversible, while the stoichiometric hydrogenation of tbe by 1 is slower and irreversible. The dinitrogen complex, [Ir{C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 }] 2 (μ-N 2 ) ( 3 ), results from the reaction of 1 with excess tbe under 1 atm of nitrogen. A single-crystal X-ray structure determination of 3 reveals a perpendicular arrangement of the P−C−P pincer ligands, which accounts for the surprising stability of 3 and the inhibiting effect of nitrogen on reactions catalyzed by 1 .