Electrophilic addition to hexafluorobut-2-yne complexes of platinum(0), rhodium(I), and iridium(I)

Abstract

The hexafluorobut-2-yne complexes, Pt(CF₃CCCF₃)L₂(L = PPh₃, PMePh₂, PMe₂Ph, PEt₂Ph; 2L = Ph₂PCH₂CH₂PPh₂) react with trifluoroacetic acid to give the square planar alkenyl complexes, Pt(OCOCF₃)(CF₃CCHCF₃)L₂ in which the phosphine ligands have a relative cis-configuration. The complex, cis-Pt(OCOCF₃)(CF₃CCHCF₃)(PPh₃)₂ can be thermally isomerised to its trans-isomer and cis–trans isomerisation also occurs in [²H₆] acetone solution. The action of heat on cis-PtCl(CF₃CCHCF₃)(PMePh₂)₂ also effects isomerisation to the trans-isomer. Mercury(II) chloride and bromide similarly react with Pt(CF₃CCCF₃)(PPh₃)₂ and Pt(CF₃CCCF₃)(PMePh₂)₂ to give the mercuriated products [PtCl{CCF₃C(HgCl)CF₃}(PPh₃)₂] and cis-[PtX{CF₃CC(HgX)CF₃}(PMePh₂)₂](X = Cl or Br). Protonation of RhCl(CF₃CCCF₃)(PPh₃)₂ and IrCl(CO)(CF₃CCCF₃)(PPh₃)₂ gives the alkenyl complexes RhCl₂(CF₃CCHCF₃)(PPh₃)₂ and IrCl(OCOCF₃)(CF₃CCHCF₃)(CO)(PPh₃)₂ respectively but W(MeCN)(CF₃CCCF₃)₃ does not react with trifluoroacetic acid under normal conditions.