Vanadium oxide anion cluster reactions with methyl isobutyrate and methyl methacrylate monomer and dimer: a study by FT/ICR mass spectrometry

Laser ablation of vanadium pentoxide (V2O5) powder produces VO3-, V2O5-, V3O7-, V3O8-, and V4O10- cluster ions which have subsequently been reacted with methyl isobutyrate, methyl methacrylate monomer and its dimer in the ion cell region of a Fourier transform ion cyclotron resonance mass spectrometer. Gas phase ion/molecule chemistry has revealed that reactivity decreases with increased mass of the vanadium oxide cluster anions. VO3-, V2O5-, and V3O7- ions react with the three reagents, methyl isobutyrate, methyl methacrylate and its dimer, respectively, either by addition of a whole reagent molecule or an associated fragment. All products formed are a result of parallel processes. V4O10- undergoes no reaction for reaction times of up to 500 s, while V3O8- adds a water molecule. Although the ions possess a net negative charge, the reactive site toward electron rich reagents such as methyl isobutyrate, methyl methacrylate and its dimer is the under-coordinated vanadium atom. This observation is supported by the lack of reactivity toward the studied reagents by those anions (V3O8- and V4O10-) whose most likely stable structures contain fully coordinated vanadium atoms. (C) 1999 Elsevier Science B.V.