Mechanism of Ru(II)-Catalyzed Olefin Insertion and C−H Activation from Quantum Chemical Studies

The mechanism of catalytic hydroarylation of olefins by the homogeneous Ru(Tp)(CO)(Ph)(NCCH_3) catalyst recently reported by Gunnoe et al. is characterized using quantum mechanics (density functional theory). The catalytic cycle features two key steps, 1,2-olefin insertion and C−H activation via an unusual mechanism, oxidative hydrogen migration. We find that these two key steps are competitive and that improving the rate of one step is detrimental to the rate of the other. The Ru catalyst has better balance and consequently higher activity than the previously explored Ir-based system.