Olefin–acetylene metal complexes: reactions of olefin–hexafluorobut-2-yne complexes of rhodium(I) with nitrogen, phosphorus, arsenic, and antimony donor ligands

Abstract

Reaction of the complex [Rh(tmhd)(C₂H₄)(C₄F₆)](tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate, C₄F₆= hexafluorobut-2-yne) with 1 mole equivalent of the ligands L[PPh₃, P(C₆H₁₁)₃, or AsPh₃] results in displacement of ethylene to afford [Rh(tmhd)L(C₄F₆)]. Similarly [Rh(tmhd)(olefin)(C₄F₆)][olefin = cycloheptene (C₇H₁₂) or cyclo-octene (C₈H₁₄)] reacts with 1 mole equivalent of PPh₃ to give [Rh(tmhd)(PPh₃)(C₄F₆)], and 1 mole equivalent of AsPh₃ reacts with [Rh(tmhd)(C₇H₁₄)(C₄F₆)] to give [Rh(tmhd)(AsPh₃)(C₄F₆)]. The complexes [Rh(tmhd)L(C₄F₆)] react with a further mole equivalent of L to give the 18-electron complexes [Rh(tmhd)L₂(C₄F₆)] and complexes of this type, [Rh(tmhd)L₂(C₄F₆)](L = PPh₃, AsPh₃, SbPh₃, PMePh₂, or PEtPh₂; 2L = Ph₂PCH₂CH₂PPh₂), are formed upon treatment of [Rh(tmhd)(C₂H₄)(C₄F₆)] with 2 mole equivalents of L. Similarly reaction of [Rh(acac)(C₂H₄)(C₄F₆)](acac = pentane-2,4-dionate) with 2 mole equivalents of L (PPh₃, PMePh₂, or SbPh₃) affords the complexes [Rh(acac)L₂(C₄F₆)]. Treatment of [Rh(tmhd)(C₂H₄)(C₄F₆)] with 1 mole equivalent of SbPh₃ gives [Rh(tmhd)(SbPh₃)₂(C₄F₆)]. In contrast to these results, the nitrogen-donor ligands (L′= pyridine, 3-methylpyridine, or 3,5-dimethylpyridine) react with the complex [Rh(tmhd)(C₂H₄)(C₄F₆)] to give the rhodacyclopent-2-ene complexes [[graphic omitted](CF₃)}(tmhd)L′₂], the pyridine (py) derivative reacting with PPh₃ to afford [[graphic omitted](CF₃)}(tmhd)(py)(PPh₃)]. Pyridine reacts with [Rh(tmhd)(C₂H₄)(C₂F₄)] to give [Rh(tmhd)(py)₂(C₂F₄)]. Hexafluorobut-2-yne reacts with [Rh(tmhd)(AsPh₃)(C₄F₆)] and [Rh(tmhd)(SbPh₃)₂(C₄F₆)] to afford the rhodacyclopentadienes [[graphic omitted](CF₃)}(tmhd)L](L = AsPh₃ or SbPh₃) respectively, and [Rh(tmhd)(AsPh₃)(C₄F₆)] reacts with tetrafluoroethylene at –95 °C to afford [Rh(tmhd)(AsPh₃)(C₂F₄)]. The complex [Rh(acac)(PPh₃)₂(C₄F₆)] reacts with carbon monoxide to give [Rh(acac)(CO)(PPh₃)]. Variable-temperature ¹⁹F n.m.r. data for the complexes [Rh(tmhd)L₂(C₄F₆)] and [Rh(acac)L₂(C₄F₆)](L = PPh₃, AsPh₃, or SbPh₃) are interpreted in terms of dissociation of the ligand L.