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Atom Transfer Radical Addition Reactions of CCl 4 , CHCl 3 , and p -Tosyl Chloride Catalyzed by Cp′Ru(PPh 3 )(PR 3 )Cl Complexes

2009; American Chemical Society; Volume: 28; Issue: 16 Linguagem: Inglês

10.1021/om900075h

1520-6041

Radhika P. Nair, Tae Ho Kim, B.J. Frost,

CO2 Reduction Techniques and Catalysts

A series of Cp′Ru(PR3)(PPh3)Cl complexes, where Cp′ = Cp*, Dp, Ind, Cp, Tp and PR3 = PTA, PMe3, PPh3, have been used to catalyze the atom transfer radical addition (ATRA) of various chloro substrates (CCl4, CHCl3, and TsCl) to styrene and/or hexene. The complexes Cp*Ru(PTA)(PPh3)Cl, Cp*Ru(PMe3)(PPh3)Cl, DpRu(PMe3)(PPh3)Cl, and TpRu(PMe3)(PPh3)Cl have been synthesized by ligand exchange reactions with Cp′Ru(PPh3)2Cl and characterized by NMR spectroscopy and X-ray crystallography. An alternative synthesis for CpRu(PMe3)(PPh3)Cl and the solid-state structure of the previously reported complex IndRu(PMe3)(PPh3)Cl are also described. Among the ruthenium(II) complexes studied, Cp*Ru(PTA)(PPh3)Cl and Cp*Ru(PMe3)(PPh3)Cl were very active at 60 °C with TOF values of 1060 and 933 h−1, respectively; Cp*Ru(PPh3)2Cl was the most active for the addition of CCl4 to styrene with a TOF >960 h−1 at room temperature. Total turnovers (TTO) in excess of 80 000 for the addition of CCl4 to hexene were obtained for the Cp* complexes, making these complexes the most active and robust catalysts for ATRA reported to date.