Hydrodefluorination and Other Hydrodehalogenation of Aliphatic Carbon−Halogen Bonds Using Silylium Catalysis

Abstract

Trialkylsilylium cation equivalents partnered with halogenated carborane anions (such as Et(3)Si[HCB(11)H(5)Cl(6)]) function as efficient and long-lived catalysts for hydrodehalogenation of C-F, C-Cl, and C-Br bonds with trialkylsilanes as stoichiometric reagents. Only C(sp(3))-halogen bonds undergo this reaction. The range of C-F bond-containing substrates that participate in this reaction is quite broad and includes simple alkyl fluorides, benzotrifluorides, and compounds with perfluoroalkyl groups attached to an aliphatic chain. However, CF(4) has proven immune to this reaction. Hydrodechlorination was carried out with a series of alkyl chlorides and benzotrichlorides, and hydrodebromination was studied only with primary alkyl bromide substrates. Competitive experiments established a pronounced kinetic preference of the catalytic system for activation of a carbon-halogen bond of a lighter halide in primary alkyl halides. On the contrary, hydrodechlorination of C(6)F(5)CCl(3) proceeded much faster than hydrodefluorination of C(6)F(5)CF(3) in one-pot experiments. A solid-state structure of Et(3)Si[HCB(11)H(5)Cl(6)] was determined by X-ray diffraction methods.

Metal Complexes with Very Large Dipole Moments: the Anionic Carborane Nitriles 12-NC–CB11X11– (X = H, F, CH3) as Ligands on Pt(II) and Pd(II)

“…UV (THF) λ max (log ε) 232 (sh) (4.07), 296 (4.45). cis-Bis(triethylphosphine)-bis (2,3,4,5,6,7,8,9,10,11-decmethyl-12-cyano-1-carba-closo-dodecaborate)platinum(II) (20). This was prepared from cis-dichlorobis(triethylphosphine)platinum(II) (12) and Cs[1-H-12-CN-CB 11 (CH 3 ) 10 ] (11), according to the general procedure GP2.…”

Proton-Catalyzed, Silane-Fueled Friedel-Crafts Coupling of Fluoroarenes

“…‡ 4 mol-%. aryl carbon-fluorine bonds appeared sufficiently inert in these studies such that aryl-fluorides could be used as solvents without interference; formation of phenyl cation was not anticipated (13,14). The driving force for the reaction comes from the substantial Si-F bond strength relative to that of the C(aliphatic)-F bond.…”

“…V enus has the most extreme atmospheric circulation of the terrestrial planets, with the cloud-level atmosphere spinning on average 60 times faster than the planet's surface (1). This superrotation (2-10) extends to both polar regions in hemispheric spiral-like patterns of clouds (11), where it results in fast rotating, infrared-bright central vortices (12)(13)(14)(15).…”

Triflyloxy-substituted carboranes as useful weakly coordinating anions

“…1A). The outcomes of these reactions 20 are analogous to those with a halogen in place of OTf. 1,13 Cesium salts of the tris-triflyloxy and mono-triflyloxy halogen substituted anions were isolated after workup with Cs 2 CO 3 followed by recrystallization.…”

“…37 Thus, although binding to the chlorine on the carborane cage is possible, even the soft Pd center prefers to bind the B-OTf oxygen in [HCB 11 Cl 10 OTf]. 20 In summary, we have developed new triflyloxy substituted carboranes for use as weakly coordinating anions. The triflyloxy moiety is chemically robust and highly useful in NMR spectroscopy studies.…”