Probing steric influences on electrophilic phosphonium cations: a comparison of [(3,5-(CF)CH)PF] and [(CF)PF].

The electrophilic phosphonium cation (EPC) salt [(3,5-(CF3)2C6H3)3PF][B(C6F5)4] (2) is prepared via oxidation of the precursor phosphine with XeF2 and subsequent abstraction of fluoride with [Et3Si(tol)][B(C6F5)4]. The Lewis acidity of 2 is evaluated by experimental and computational methods and by preliminary catalysis testing. Exchange reactions of 2 and [(C6F5)3PF][B(C6F5)4] with their respective difluorophosphoranes are studied by 2D 19F-19F NOESY/EXSY and selective 1D 19F NMR exchange spectroscopy (SEXSY) experiments affording comparative rates of fluoride exchange.

Electrophilic phosphonium cations (EPCs) with perchlorinated-aryl substituents: towards air-stable phosphorus-based Lewis acid catalysts.

A series of phosphines incorporating (C6Cl5) substituents, Ph2P(C6Cl5) 1, PhP(C6Cl5)22, P(C6Cl5)33 and (C6F5)P(C6Cl5)24 were prepared. In the case of 1, 2 and 4, these were converted to the corresponding aryl-difluorophosphoranes 5-7via reaction with XeF2, whereas reaction of 3 with XeF2 afforded only an inseparable mixture of products. The compounds 5-7 were converted to the fluorophosphonium cations 8-10, whereas the reaction of 3 with Selectfluor afforded (C6Cl5)2POF and (C6Cl5)2.

Reactions of iodine-nitrene reagents with boranes.

Reactions of the boranes (C6F5)2BR (R = C6F5, Ph, H) with the nitrene-iodine reagents XC6H4SO2N=IPh, X = Me, Cl and MeSO2N=IPh effect the insertion of nitrene into the B–C and B–H bonds affording the species (C6F5)2BN(SO2C6H4X)R (X = Me, R = C6F5 1, Ph 3, H, 4, X = Cl, 5, X = NO2, 7) and (C6F5)2BN(SO2Me)H 6).