Atom Transfer Radical Additions with the Cationic Half‐Sandwich Complex [Cp*Ru(PPh3)2(CH3CN)]OTf

The cationic ruthenium half‐sandwich complex [Cp*Ru(PPh3)2(CH3CN)][OTf] (2) (Cp* = η5‐C5Me5, OTf = SO3CF3) was synthesized by reduction of [Cp*RuCl2]2 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]2[ZnCl4] (3) and [Cp*Ru(PPh3)2(CH3CN)]2[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*RuCl(PPh3)2]. For the addition of CHCl3 to styrene, a total turnover number of 890 was achieved. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)