Gas-Phase Reactivity of Lanthanide Cations with Fluorocarbons:  C−F versus C−H and C−C Bond Activation

The gas-phase reactivity of the fluorinated hydrocarbons CF 4, CHF 3, CH 3 F, C 2 F 6, 1,1-C 2 H 4 F 2, and C 6 F 6 with the lanthanide cations Ce +, Pr +, Sm +, Ho +, Tm +, and Yb + and the reactivity of C 6 H 5 F with all lanthanide cations Ln + (Ln = La−Lu, with the exception of Pm + ) have been examined by Fourier-transform ion cyclotron resonance mass spectrometry. The perfluorinated compounds tetrafluoromethane and hexafluoroethane as well as trifluoromethane do not react with any lanthanide cation. Selective activation of the strong C−F bonds in fluoromethane, 1,1-difluoroethane, hexafluorobenzene, and fluorobenzene appears as a general reaction scheme along the 4f row. Experimental evidence is given for a “harpoon”-like mechanism for the F atom abstraction process which operates via an initial electron transfer from the lanthanide cation to the fluorinated substrate in the encounter complex Ln + RF. The most reactive lanthanides La +, Ce +, Gd +, and Tb + and also the formal closed-shell species Lu + exhibit additional C−H and C−C bond activation pathways in the reaction with fluorobenzene, namely dehydrohalogenation as well as loss of a neutral acetylene molecule. In the case of Tm + and Yb + the formation of neutral LnF 3 is observed in a multistep process via C−C coupling and charge transfer.