Reactions of donor-free (CF3)2Cd with phosphorus(V) halides:: Insertion of difluorocarbene and direct synthesis of (CF3)3PF2

Difluorocarbene which is quantitatively eliminated from donor-free bis(trifluoromethyl)-cadmium below 0 ?C inserts smoothly into the P-F bonds of PF5 to form (CF3)(3)PF2 in high yield. Due to the fast conversion of P-Cl bonds into P-F bonds by cadmium fluoride, PCl5 forms (CF3)(3)PF2 as well, and a direct synthesis of (CF3)(3)PF2 with ca. 70 % yield starting from CdEt2, CF3I and PCl5 is reported. Whereas no insertion of CF2 into the axial bonds of (CF3)(3)PF2 has been detected, reaction of (CF3)(2)Cd with (CF3)(3)PCl2 gives the new tetrakis(haloalkyl)fluorophosphoranes (CF3)(3)(CF2Cl)PF, (CF3)(3)(CFCl2)PF (CF3)(2)(CF2Cl)(2)PF and (CF3)(3)(CCl3)PF. The NMR spectra of these and related compounds and of their hydrolysis products (CF3)(3)(CF3-nCln)PO are reported. The formation of the higher chlorinated phosphoranes is discussed in terms of an isomerization mechanism presumably involving carbene elimination-reinsertion processes.