Atom transfer radical additions with the cationic half-sandwich complex [Cp*Ru(PPh3)(2)(CH3CN)]OTf

The cationic ruthenium half-sandwich complex [CpRu(PPh3)(2)(CH3CN)][OTf] (2) (CP = eta(5)-C5Me5, OTf = SO3CF3) was synthesized by reduction of Cp*RuCl2 with zinc in the presence of NaOTf and subsequent reaction with PPh3. When NaOTf was omitted, the corresponding tetrachlorozincate salts were obtained. Complex 2, as well as the salts Cp*Ru(CH3CN)(3)[ZnCl4] (3) and Cp*Ru(PPh3)(2)(-)(CH3CN)[ZnCl4] (4), were characterized by single-crystal X-ray analysis. Complex 2 proved to be a potent catalyst for the atom transfer radical addition of CCl4 and CHCl3 to terminal olefins, displaying a performance superior to that of the previously described neutral catalyst [Cp*RuCI(PPh3)(2)]. For the addition of CHCl3 to styrene, a total turnover number of 890 was achieved. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).