No abstract

The 16-electron ruthenium(II) complexes [RuCl(dppe) 2 ]PF 6 (2; dppe ) 1,2-bis(diphenylphosphino)ethane), [RuCl(chiraphos) 2 ]PF 6 (3; chiraphos ) (S,S)-3,4-bis(diphenylphosphino)butane), and [RuCl(PNNP)]PF 6 (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 (CH 3 ) 3 CX (X ) Br, 5c; X ) I, 5d), Ph 2 CHBr (6c), and PhCH(Me)Br (7c) are converted to the fluoro analogues in the presence of TlF 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 difluorobridged thallium adduct [Tl(µ-F) 2 Ru(dppe) 2 ]PF 6 (9) was observed by 31 P NMR during catalysis with 2 and independently prepared by reaction of 2 with TlF (2 equiv). Complex 9 was characterized by 1 H, 31 P, 19 F, and 205 Tl NMR spectroscopy, as well as by X-ray diffraction.

The five-coordinate fluoro complex [RuF(dppp) 2 ]PF 6 (1a) has been prepared by reacting [RuCl(dppp) 2 ]PF 6 (1b) with TlF (dppp ) 1,3-bis(diphenylphosphino)propane). An X-ray investigation of 1a shows a distorted trigonal bipyramidal geometry (Y-shaped). The 16electron complex 1a reacts with a number of donors, including CO, H 2 , and F -. The X-ray structure of trans-[RuF(CO)(dppp) 2 ]PF 6 (2aBPh 4 ) suggests that the π-donor ability of the fluoro ligand is only slightly higher than that of chloride. The reaction of 1a with [Me 4 N]F gives cis-[RuF 2 (dppp) 2 ] (3), a rare difluoro complex not stabilized by π-acidic co-ligands. The Ru-F bond of 1a is hydrogenolyzed upon reaction with H 2 to give [RuH(η 2 -H 2 )(dppp) 2 ] + . The coordinatively unsaturated complex 1a reacts with activated haloalkanes R-X (X ) Cl or Br) in 1:1 molar ratio to give the fluorinated organic derivative and [RuX(dppp) 2 ] + . The halide metathesis proceeds instantaneously and quantitatively with (E)-3-bromo-1,3diphenylpropene and chlorotriphenylmethane. Substrate conversion decreases with decreasing substitution at the halogen-bearing carbon atom.

No abstract

Dioxygen addition to the 16-electron complexes [OsX(P-P)2]+ (3) gives the dioxygen adducts [OsCl(eta 2-O2)(P-P)2]+ (3), which in turn react with HCl gas to give the novel osmium(IV) oxo complexes trans-[OsX(O)(P-P)2]+ (5) (X = Cl, Br; P-P = 1,2-bis(dicyclohexylphosphino)ethane (dcpe), 1,2-bis(diethylphosphino)ethane (depe), 1,2-bis((2R,5R)-2,5-dimethylphospholano)benzene (Me-duphos)). The complexes [OsX(dcpe)2]+ (X = Cl, Br) (3) are studied by X-ray crystallography and are shown to have a "Y-shaped" coordination geometry in the equatorial plane. The X-ray structural analysis of [OsCl(eta 2-O2)(dcpe)2]+ (4a) reveals an exceptionally short O-O bond (1.315(5) A). trans-[OsCl(O)(dcpe)2]+ (5a), the first oxo complex of osmium(IV) investigated crystallographically, exhibits a long Os-O distance of 1.834(3) A. The reactivity of 4 and 5 as oxidants is described. The dioxygen complex 4a transfers one oxygen atom to PPh3 (to give Ph3PO) or oxidizes iodide ions to triiodide ions in the presence of anhydrous HCl. In both reactions, the corresponding oxo species 5a is quantitatively formed as the only metal-containing product. Oxo complexes 5 are surprisingly stable and unreactive toward standard reducing agents such as phosphines.