Acid-Promoted Hydrogen Migration in (2-Allylphenoxo)ruthenium(II) To Form an η³-Allyl Complex

Treatment of RuCp[OC6H4(CH2CHCH2-2)-κ1O:η2C,C′](PPh3) (3c) with a Brønsted acid (HX) such as 2-allylphenol results in facile migration of a benzylic proton to the aryloxide, giving the (η3-allyl)ruthenium(II) complex RuCp[CH2CHCH(C6H4OH-2)-η3C,C′,C′′](PPh3) (4c). Thermodynamic and kinetic studies suggest that 3c associates with acid to give 3c·HX, and further addition of HX to 3c·HX causes the C−H bond cleavage reaction to give 4c.