A series of new fluororhodium(I) complexes†

Abstract

The reaction of [Rh{η²-O₂S(O)CF₃}(PPrⁱ₃)₂] 1 with terminal alkynes RCCH (R = Ph or Bu^t) led to the formation of the vinylidene compounds trans-[Rh{η¹-OS(O)₂CF₃}(CCHR)(PPrⁱ₃)₂] 2a,2b, which on treatment with tetrabutylammonium fluoride hydrate or KF gave the fluororhodium(I) complexes trans-[RhF(CCHR)(PPrⁱ₃)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(µ-F)(PPrⁱ₃)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′)(PPrⁱ₃)₂], of which that with L′ = C₂H₄ was characterized by X-ray crystallography. In contrast to the hydroxo compound trans-[Rh(OH)(CCHPh)(PPrⁱ₃)₂], which on treatment with acids HX (X = CF₃SO₃, CH₃CO₂, PhO or PhCC) gave trans-[RhX(CCHPh)(PPrⁱ₃)₂], the fluoro derivative 3a reacts only with CF₃SO₃H and PhCCH 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)(CCHPh)(PPrⁱ₃)₂] and probably trans-[Rh(FHF)(CCHPh)(PPrⁱ₃)₂].