REACTIVITY OF LANTHANIDE, GROUP-2, AND GROUP-3 METAL AND METAL-OXIDE CATIONS WITH PENTAMETHYLCYCLOPENTADIENE - GAS-PHASE SYNTHESIS OF CYCLOPENTADIENYL CATIONS

The gas-phase reactivity of lanthanide (Ln(+) = La+-Lu+), group 2 (Ca, Sr+, and Ba+), and group 3 (Sc+ and Y+) cations, and of their corres ponding monoxide ions MO+, with pentamethylcyclopentadiene (C5Me5H) wa s studied by Fourier transform ion cyclotron resonance mass spectromet ry. The reactivity of Eu+, Tm+, Yb+, and the alkaline earth metal ions was similar to that observed previously for Sm+, namely formation of the fulvenide ion M(C5Me4CH2)(+) as the main primary product and the m etallocene ion M(C5Me5)(2)(+) as the main secondary product. With Sc+, Y+, and the remaining lanthanide series ions, several other species w ere observed in the primary reactions, corresponding to single and mul tiple losses of neutral molecules such as H-2 and CH4. These differenc es in reactivity appear to correlate with the accessibility of reactiv e excited state electron configurations of the metal ions. In the case of the metal oxide cations MO+, the reactivity with pentamethylcyclop entadiene appears to be determined by the strength of the M+-O bonds. The ions with the strongest bonds, LaO+, CeO+, PrO+, and NdO+, formed M(C5Me5)(OH)(+) as the sole primary product, which reacted further, el iminating water, to give the metallocene ion M(C5Me5)(2)(+). ScO+, YO, and the lanthanide series ions SmO+, GdO+-TmO+, and LuO+ yielded MO( C5Me4CH2)(+) and M(C5Me4CH2)(+) as the primary products in addition to M(C5Me5)(OH)(+). These metal oxides gave M(C5Me4CH2)(2)(+) and M(C5Me 2)(2)(+) as secondary products. The ions with the weakest M+-O bonds, EuO+, YbO+, CaO+, SrO+, and BaO+, formed MOH+ as a primary product and M(C5Me5)(+) as a secondary product.