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fluorine atoms from a variety of perfluoroolefins including perfluoro-2,4-dimethyl-3-ethylpent-2-ene, perfluoro-2,3-dimethylpent-2-ene, and perfluorocyclohexene. A similar abstraction of fluorine atoms from perfluorobenzene is much slower. However, visible light enhances the rate of fluorine abstraction from perfluorobenzene by MCp*2-OEt2 (M = Yb, Eu, Sm). Qualitative observation shows that the relative fluorine abstraction reactivity of the four lanthanoid complexes increases with increasingly negative reduction potential for reasonably unhindered fluoroolefin substrates. The Yb(III)/Yb(II) reduction potential of YbCp'2 solvated in acetonitrile is determined here to be -1.65 V (relative to ferrocene) by cyclic voltammetry. The fully characterized organometallic products from the fluorine atom abstraction reactions are solvated trivalent lanthanoid fluorides MCp*2F-L (M = Yb, Eu, Sm; L = diethyl ether or THF) and YbCp'2F-THF. The molecular structures of YbCp*2F-OEt2 and YbCp*2F-THF determined by X-ray crystallography reveal the first terminal lanthanoid-fluoride bonds. However, three different environments for bridging lanthanoid-fluoride bonds are seen in the X-ray determined structure of the trivalent pentaytterbium cluster [Yb5Cp*6(/u4-F)(M3-F)2(M-F)6], which is a secondary product from the further reaction of YbCp*2F with perfluoroolefins. From the X-ray data of these three trivalent ytterbium compounds the averaged Yb-F distances are 2.02 A for the terminal Yb-F bonding mode, 2.20 A for an F atom bridging between two Yb atoms, and 2.37 A for an F atom bridging between three of four Yb atoms.

Bis(pentamethylcyclopentadienyl)lutetium complexes Lu( 75-C5Me5) 2R (R = Me, H) react at 20-50 "C in hydrocarbon solvents with benzene, pyridine, the ylide CH2PPh3, and tetramethylsilane to give stable, isolatable products of C-H activation, i.e. metallation at a carbon of the reagent with extrusion of R-H.I report here that lutetium-alkyl and -hydride derivatives can activate sp2 C-H bonds in both intra-and inter-molecular reactions and even activate the sp3 bonds of SiMe,. That these reactions occur under mild conditions with hydrocarbons of very low acidity is extraordinary for stable, isolatable complexes.The hydride Lu(q5-C5Me5),H (2) [VL" -H(Nujol) 1345 cm-'1 is readily formed?' by hydrogenolysis of (1) [reaction (i), Scheme 1 ; pentane solution, 20 "C, 1 atm H,]. This hydride rapidly undergoes H / D exchange when dissolved in deuteriated arenes [benzene or toluene, reaction (ii)] at 20 "C forming the deuteride, Lu(q5-CSMe5),D [vLu-D(NujoI) 975 cm-l]. As shown in reaction (ii), Scheme 1, exchange with D, also occurs in pentane at 20 "C.A more important non-degenerate intermolecular C-H activation between the hydride (2) and benzene occurs

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