Abstract: | Twenty-six monoalkoxyfluorophosphoranes bearing an asymmetric substituent of types R1PF3(OR2*)( 1 ), R1*PF3(OR2) ( 2 ), R1R3PF2(OR2* 3 ) and R21PF2(OR2*)( 4 ), have been prepared. The non-equivalence of the axial fluorine atoms is observed in the 19F NMR spectra for the compounds of types 1 δF′a – δF′a ~ 0·5 to 3·8 ppm, J(FaF′a) ~ 10 Hz, 2 δFa – δF′a ~ 1·1 to 1·5 ppm, J(FaF′a) ~ 14 Hz and 3 δFa – δFa ~ 0·2 ppm, J(FaF′a) ~ 10 Hz but not for those of type 4 R12PF2(OR2*). Its origin is assigned to the diastereotopic character of these fluorines. The possibility of a hindered rotation of the substituents as the origin of the phenomenon is excluded. The preparation of sec-BuPF4 and EtPhPF3 is also reported. |