Methane Activation by (MoO 3 ) 5 O - Cluster Anions: The Importance of Orbital Orientation.

The reactivity of the molybdenum oxide cluster anion (MoO ₃ ) ₅ O ^- , bearing an unpaired electron at a bridging oxygen atom (O _b ^.- ), towards methane under thermal collision conditions has been studied by mass spectrometry and density functional theory calculations. This reaction follows the mechanism of hydrogen atom transfer (HAT) and is facilitated by the O _b ^.- radical center. The reactivity of (MoO ₃ ) ₅ O ^- can be traced back to the appropriate orientation of the lowest unoccupied molecular orbitals (LUMO) that is essentially the 2p orbital of the O _b ^.- atom. This study not only makes up the blank of thermal methane activation by the O _b ^.- radical on negatively charged clusters but also yields new insights into methane activation by the atomic oxygen radical anions.
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