Bis(pentafluorophenyl)ytterbium, prepared from reaction of bis(pentafluorophenyl)mercury with ytterbium metal in tetrahydrofuran (THF), has been isolated as the highly air-sensitive, thermally unstable complex (C6F5)2Yb(THF)4, which yielded pentafluorobenzene on acidolysis. The 19F NMR, IR, and UV/Vis spectra of the complex are discussed. A tetrahydrofuran complex of bis(2,3,5,6-tetrafluorophenyl)ytterbium has been prepared in a similar manner and was identified spectroscopically, thermal instability preventing satisfactory analytical characterization. Reaction was observed between ytterbium and bis(2,3,4,5-tetrafluorophenyl)mercury, but the product decomposed too rapidly for isolation. Ytterbium metal failed to react with diphenylmercury or bis(Dentachlorophenyl)mercury.