C−H Activation by Iron‐Vanadium Bimetallic Oxide Cluster Anions FeV3O10− and FeV5O15−: A Comparison with Scandium‐Vanadium Oxide Clusters

Hydrogen atom abstraction from C₂−C₄ alkanes at 298 K by iron-vanadium bimetallic oxide cluster anions FeV₃O₁₀ ⁻ and FeV₅O₁₅ ⁻ featuring iron-bonded O⋅⁻ radicals (Fe−O⋅⁻) is characterized experimentally, which offers a new regulation rule to tune the activity of M−O⋅⁻ radicals.

Abstract

Late transition metal-bonded atomic oxygen radicals (LTM−O⋅⁻) have been frequently proposed as important active sites to selectively activate and transform inert alkane molecules. However, it is extremely challenging to characterize the LTM−O⋅⁻-mediated elementary reactions for clarifying the underlying mechanisms limited by the low activity of LTM−O⋅⁻ radicals that is inaccessible by the traditional experimental methods. Herein, benefiting from our newly-designed ship-lock type reactor, the reactivity of iron-vanadium bimetallic oxide cluster anions FeV₃O₁₀ ⁻ and FeV₅O₁₅ ⁻ featuring with Fe−O⋅⁻ radicals to abstract a hydrogen atom from C₂−C₄ alkanes has been experimentally characterized at 298 K, and the rate constants are determined in the orders of magnitude of 10⁻¹⁴ to 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹, which are four orders of magnitude slower than the values of counterpart ScV₃O₁₀ ⁻ and ScV₅O₁₅ ⁻ clusters bearing Sc−O⋅⁻ radicals. Theoretical results reveal that the rearrangements of the electronic and geometric structures during the reaction process function to modulate the activity of Fe−O⋅⁻. This study not only quantitatively characterizes the elementary reactions of LTM−O⋅⁻ radicals with alkanes, but also provides new insights into structure-activity relationship of M−O⋅⁻ radicals.

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