Atom Transfer Radical Additions with the Cationic Half‐Sandwich Complex [Cp*Ru(PPh 3 ) 2 (CH 3 CN)]OTf

The cationic ruthenium half‐sandwich complex [Cp*Ru(PPh 3 ) 2 (CH 3 CN)][OTf] ( 2 ) (Cp* = η 5 ‐C 5 Me 5 , OTf = SO 3 CF 3 ) was synthesized by reduction of [Cp*RuCl 2 ] 2 with zinc in the presence of NaOTf and subsequent reaction with PPh 3 . When NaOTf was omitted, the corresponding tetrachlorozincate salts were obtained. Complex 2 , as well as the salts [Cp*Ru(CH 3 CN) 3 ] 2 [ZnCl 4 ] ( 3 ) and [Cp*Ru(PPh 3 ) 2 (CH 3 CN)] 2 [ZnCl 4 ] ( 4 ), were characterized by single‐crystal X‐ray analysis. Complex 2 proved to be a potent catalyst for the atom transfer radical addition of CCl 4 and CHCl 3 to terminal olefins, displaying a performance superior to that of the previously described neutral catalyst [Cp*RuCl(PPh 3 ) 2 ]. For the addition of CHCl 3 to styrene, a total turnover number of 890 was achieved. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)