XeF₂/Fluoridakzeptoren als vielseitige Einelektronen‐Oxidationsmittel

Abstract

Kein Phlogiston aber Xenon entweicht, wenn XeF2/F−‐Akzeptoren als neue Einelektronen‐Oxidationsmittel agieren. F−‐Akzeptoren sind zum einen Lewis‐Säuren BF3, B(C6F5)3, Al{OC(CF3)3}3 und zum anderen Silylderivate TfOSiMe3, Tf2NSiMe3, Me3Si+ B(C6F5)4−, Me3Si+ CHB11Cl11−. Dabei können in Oxidationsprodukte von R2E2 (E=S, Se, Te), [FeCp2], [(FeCpS)4], TTF, Thianthren und (2,4‐Br2C6H3)3N die Anionen BF4−, TfO−, Tf2N−, FB(C6F5)3−, FAl{OC(CF3)3}3−, B(C6F5)4− oder CHB11Cl11− eingeführt werden.

Mechanistic Studies on the Anodic Functionalization of Alkenes Catalyzed by Diselenides

“…Having in mind that adduct 2a is formed very rapidlymore rapidly than the formation of [PhSe] + after initial one electron oxidation of 1a in a second order process with regard to 1a and that 1a + did not show any reversibility even at high scan rates, we propose a very rapid formation of tetrameric dication [(PhSe) 4 ] 2+ upon initial oxidation of 1a (i.e., dimerization of 1a + ) . Such dimerizations of organoselenium cations have precedents in the literature. , Dications with the generic composition [R 4 E 4 ] 2+ (R = Et, Me; E = Se, Te) were isolated and fully characterized after chemical one-electron-oxidation of the corresponding dichalcogenides (R 2 E 2 ). Such reactivity is very similar to what is proposed herein after the electrochemical oxidation of 1a .…”

“…Such reactivity is very similar to what is proposed herein after the electrochemical oxidation of 1a . Notably, analogous tetrameric dications possessing nonstabilizing aryl substituents were not isolable. , This circumstance is in line with the proposed formation of [PhSe] + and [(PhSe) 3 ] + after electrochemical oxidation of 1a in the absence of 3a as well as the formation of the trimeric species after substoichiometric chemical oxidation of 1a . A dicationic tetramer could well decompose yielding [PhSe] + and [(PhSe) 3 ] + , though the latter can also be formed in a reaction of in situ formed [PhSe] + and 1a .…”

Al(OCArF3)3 – a thermally stable Lewis superacid

“…Due to its limited thermal stability it is usually prepared in situ and used as fluorobenzene adduct with a lower FIA (465 kJ mol –1 ) 9. Another drawback is the tendency of the corresponding WCAs, [Al(OC(CF 3 ) 3 ) 4 ] – or [FAl(OC(CF 3 ) 3 ) 3 ] – , to suffer from severely disordered crystal structures 10. The vital interest in new Lewis superacids with more refined properties is highlighted by five recent publications: Mitzel et al improved the Lewis acidity of BCF by substitution of its para -positions by CF 3 groups resulting in the strongest single-site triorganoborane Lewis acid B(C 6 F 4 CF 3 ) 3 11.…”

Diaryldichalcogenide radical cations

“…Another one-electron oxidation eventually yields the thianthrene radical cation ( 6 ) and unaccounted products ( Scheme 1 ). 8 The one-electron oxidation of (PhS) 2 ( 1a ) and its Se-congener (PhSe) 2 ( 1b ) in the confined voids of the acidic pentasil zeolithe allowed the tentative characterization of the radical cations [(PhS) 2 ]˙ + ( 2a ) and [(PhSe) 2 ]˙ + ( 2b ) by EPR spectroscopy. 9 Previous attempts to prepare a persistent dialkyldisulfide radical cation using (NeoS) 2 ( 7 ; Neo = neopentyl) and nitrosyl triflate [NO][O 3 SCF 3 ] afforded a dialkyldisulfide nitrosonium adduct [(NeoS) 2 ·NO] + ( 8 ) comprising a four-membered ring structure ( Scheme 2 ).…”