Gas-phase reactivity of rare earth cations with phenol: Competitive activation of C-O, O-H, and C-H bonds

The gas-phase reactions of Sc⁺, Y⁺, and Ln⁺ (Ln=La-Lu, except Pm) ions with phenol were studied by Fourier transform ion cyclotron resonance mass spectrometry. All the ions except Yb⁺ were observed to react with the organic substrate, activating O-H, C-O, and/or C-H bonds, with formation of MO⁺, MOH⁺, and/or MOC₆H ₄ ⁺ ions as primary products. The product distributions and the reaction efficiencies obtained showed the existence of important differences in the relative reactivity of the rare earth metal cations, which are discussed in terms of factors like the electron configurations of the metal ions, their oxophilicity, and the second ionization energies of the metals. The primary product ions participated in subsequent reactions, yielding species such as M(OH)(OC₆H₅)⁺, which lead mainly to M(OC₆H₅)₂(HOC₆H₅) _n ⁺ ions, where n=0–2. Formation of M(OC₆H₅)(HOC₆H₅) _n ⁺ species was also observed in the case of the metals that have high stabilities of the formal oxidation state 2+, Sm and Eu.