Reactivity control of C-H bond activation over vanadium-silver bimetallic oxide cluster cations

Vanadium-silver bimetallic oxide cluster ions (V(x)Ag(y)O(z)(+); x=1-4, y=1-4, z=3-11) are produced by laser ablation and reacted with ethane in a fast-flow reactor. A reflectron time of flight (Re-TOF) mass spectrometer is used to detect the cluster distribution before and after the reactions. Hydrogen atom abstraction (HAA) reactions are identified over VAgO(3)(+), V(2)Ag(2)O(6)(+), V(2)Ag(4)O(7)(+), V(3)AgO(8)(+), V(3)Ag(3)O(9)(+), and V(4)Ag(2)O(11)(+) ions, in which the oxygen-centered radicals terminally bonded on V atoms are active sites for the facile HAA reactions. DFT calculations are performed to study the structures, bonding, and reactivity. The reaction mechanisms of V(2)Ag(2)O(6)(+) +C(2)H(6) are also given. The doped Ag atoms with a valence state of +1 are highly dispersed at the periphery of the V(x)Ag(y)O(z)(+) cluster ions. The reactivity can be well-tuned gradually by controlling the number of Ag atoms. The steric protection due to the peripherally bonded Ag atoms greatly enhances the selectivity of the V-Ag bimetallic oxide clusters with respect to the corresponding pure vanadium oxide systems.