Reactions of some ethers with transition-metal fluorides and xenon difluoride.

The reactions of fluoro-, chlorofluoro- and chloro-ethers with high-valent transition-metal fluorides and XeF2 have been studied. These investigations have shown that high- oxidation state transition-metal fluorides react with both fluoro- and chlorofluoro-ethers to yield fluorination and/or cleavage products. Cleavage occurs only when a CF2 group is adjacent to the oxygen, although the presence of this group does not necessarily lead to reaction. The products formed from this cleavage are alkyl- and acyl-fluorides. Early transition-metal fluorides tend to cleave the ethers whilst later transition-metal fluorides tend to yield fluorination products. Selective fluorination is only observed for VF5 and IrF6, when reacted with CF2HOCHClCF3, yielding exclusive H/F and Cl/F exchange respectively. Chloroethers react with the more aggressive transition-metal fluorides to give degradation of the ether, while the less reactive fluorides possibly give complexes. With XeF2 the ethers react unselectively to yield a number of fluorinated products. Addition of AHF was needed to facilitate reaction. Experiments with XeF2 in the presence of NaF, BF3, HCl and CF3SO3H indicate that the reaction mechanism involves XeF+ and not due to protonation of the ether nor due to the presence of F-. A full mechanism is proposed. The reactions of UF6 with ethers show a similar unselectivity to that observed for the reactions with XeF2, although UF6 was found to be less potent. As seen in the reactions of the high-valent transition-metal fluorides with ethers, these reactions of UF6 result in cleavage as well as fluorination. Reaction products have been characterized by 1H, 19F, and 13C DEPT NMR spectroscopies.