Gas Phase Reactivity of [Mo 6 X 14 ] 2- Dianions (X = Cl - I).

We investigate collision-induced dissociation (CID) of [Mo ₆ X ₁₄ ] ^2- (X = Cl, Br, I) and the reactivity of fragment ions of these precursors with background gases. Ion mobility measurements and theoretical calculations provide structural information for some of the observed ions. Sequential losses of MoX ₂ units dominate the dissociation pathways of [Mo ₆ Cl ₁₄ ] ^2- . Meanwhile, loss of X radicals is the main channel for X = Br and I. Ion mobility measurements and computational investigations indicate minor structural changes in the octahedral Mo ₆ unit for [Mo ₆ I _m ] ^- ( m = 6-13) fragments. We observe that mass spectra obtained using CID substantially vary among mass spectrometers: Specifically, ions with molecular formula [Mo ₆ X _m (O ₂ ) _n ] ^- (X = Br and I) are observed as dominant species produced through reactions with O ₂ in several mass spectrometers, but also adduct free fragment ions were observed in other instruments, depending on the background conditions. Ion-trap fragmentation combined with theoretical investigations indicates that spontaneous losses of X radicals occur upon binding of O ₂ to [Mo ₆ I _m ] ^- fragments ( m ≤ 12). Theoretical investigations indicate that both oxygen atoms are bound to the vacant sites of the Mo ₆ units. This study opens up a new vista to generate and study a large variety of hexanuclear Mo ₆ X _m (O ₂ ) _n anions.