Organoxenonium salts

Organoxenonium Salts Synthesis by "Xenodeborylation", Reactivities, andNMR Spectroscopic Properties... 

The remaining three chapters (Chapters 20-22) concentrate fully on onium ion chemistry. In Chapter 20, H.-J. Frohn and V. V. Bardin describe synthesis and multi-nuclear NMR studies of organoxenonium salts. Chapter 21 by R. S. Brown et al. focuses on the synthesis of chiral... 

The First Decade of C-Xe Chemistry Fundamental Aspects of the Syntheses of Organoxenonium Salts... 

Reactions of organoxenonium salts [RXe][EFn+)] with Lewis acids do not result in transformation of the organo group of the cation [RXe]+ (6), but rather give rise to fluoride abstraction from the counteranion [EFn+i]. For example, organoxenonium fluoroborates were converted into [EF6]" salts by using arsenic or antimony pentafluoride or their adducts, EFj L (eqs 9, 10) (22, 30). 

The reactivity of organoxenonium salts [RXe]Y towards anions X is determined by the nucleophilicity of the latter and nature of solvent. When X is a weakly nucleophilic anion, anion exchange (metathesis) occurs in polar solvents forming the corresponding [RXe]X salts in high yields (eqs 11,12). 

The choice of an appropriate solvent is determined by the ionic character of organoxenonium salts, [RXe]Y, and their reactivity. One of the most suitable solvents is aHF because it possesses a high solvating ability and chemical stability towards oxidizing compounds. The salts [RXe]Y exist in aHF solution... 

Aromatic compounds are the only type of i-nucleophiles involved in reactions with organoxenonium salts. While pentafluorobenzenes, CeFsZ (Z = H, F, CN, SiMej), are not reactive towards [C6F5Xe][AsF6] in MeCN at 20 °C, a series of 2,3,4,5,6-pentafIuorobiphenyls was obtained from monosubstituted benzene derivatives, CeHsZ, under these conditions. The reaction rates diminish in the sequence Z = CH3 > F > CF3 CN > NO2, which is consistent with the electrophilic nature of the process. Nevertheless, the isomer distribution in the C6F5C6H4Z products shows unambiguously the radical character of the pentafluorophenylation reaction (eq 17) 46). 

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