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 corresponding monoxide ions MO+, with pentamethylcyclopentadiene (C5Me5H) was studied by Fourier transform ion cyclotron resonance mass spectrometry. 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 metallocene ion M(C5Me5)(2)(+) as the main secondary product. With Sc+, Y+, and the remaining lanthanide series ions, several other species were observed in the primary reactions, corresponding to single and multiple losses of neutral molecules such as H-2 and CH4. These differences in reactivity appear to correlate with the accessibility of reactive excited state electron configurations of the metal ions. In the case of the metal oxide cations MO+, the reactivity with pentamethylcyclopentadiene 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, eliminating 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(C5Me2)(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.