A series of new fluororhodium(I) complexes

The reaction of [Rh{eta(2)-O2S(O)CF3}(PPr3i)(2)] 1 with terminal alkynes RC=CH (R = Ph or Bu-t) led to the formation of the vinylidene compounds trans-[Rh{eta(1)-OS(O)(2)CF3}(=C=CHR)(PPr3i)(2)] 2a,2b, which on treatment with tetrabutylammonium fluoride hydrate or KF gave the fluororhodium(I) complexes trans-[RhF(=C=CHR)(PPr3i)(2)] 3a,3b in ca. 70% yield. An alternative route for the preparation of 3a (R = Ph) is based on the reaction of phenylacetylene with the dimer [{Rh(mu-F)(PPr3i)(2)}(2)] 4, the latter being obtained from 1 and [NBu4]F hydrate as starting materials. Compound 4 reacts smoothly with L' = CO, CNC6H3Me2-2,6, C2Ph2 and C2H4 to afford the mononuclear complexes trans-[RhF(L')(PPr3i)(2)], of which that with L' = C2H4 was characterized by X-ray crystallography. In contrast to the hydroxo compound trans-[Rh(OH)(=C=CHPh)(PPr3i)(2)], which on treatment with acids HX (X = CF3SO3, CH3CO2, PhO or PhC=C) gave trans-[RhX(=C=CHPh)(PPr3i)(2)], the fluoro derivative 3a reacts only with CF3SO3H and PhC=CH by ligand substitution to yield the corresponding compounds. Acetic acid and phenol interact with 3a via XH ... FRh hydrogen bridges to form 1 : 1 adducts, of which that with X = CH3CO2 rearranges to give trans-[Rh(O2CMe)(=C=CHPh)(PPr3i)(2)] and probably trans-[Rh(FHF)(=C=CHPh)(PPr3i)(2)].