Catalytic fluorination by halide exchange with 16-electron ruthenium(II) complexes.: X-ray structure of [Tl(μ-F)2Ru(dppe)2]PF6

The 16-electron ruthenium(II) complexes [RuCl(dppe)(2)]PF6 (2; dppe = 1,2-bis(diphenylphosphino)ethane), [RuCl(chiraphos)(2)]PF6 (3; chiraphos = (S,S)-3,4-bis(diphenylphosphino)butane), and [RuCl(PNNP)]PF6 (4; PNNP = (1S,2S)-N,N ' -bis[2-(diphenylphosphino)benzylidene]diaminocyclohexane) catalyze the nucleophilic fluorination of activated alkyl halides with a catalyst loading as low as 1 mol%. The alkyl halides (CH3)(3)CX (X = Br, 5c; X = I 5d), Ph2CHBr (6c), and PhCH(Me)Br (7c) are converted to the fluoro analogues in the presence of TIF as the fluoride source. Yields are between 31 and 83%. The chiral complex 4 converts 7c to PhCH(Me)F (7a) with 49% yield after 24 h. At 1% conversion, 7a is nonracemic (16% ee), Which indicates that kinetic resolution occurs, albeit at a low level. The fluorination of 1,2-dibromo-1,2,3,4-tetrahydronaphthalene (8c) is highly regioselective and gives 1-fluoro-2-bromo-1,2,3,4-tetrahydronaphthalene (8a) in 68% yield. The difluoro-bridged thallium. adduct [TI(mu -F)(2)Ru(dppe)(2)]PF6 (9) was observed by P-31 NMR during catalysis with 2 and independently prepared by reaction of 2 with TIF (2 equiv). Complex 9 was characterized by H-1, P-31, F-19, and (TI)-T-205 NMR spectroscopy, as well as by X-ray diffraction.