Size-dependent reactivity of VnO+ (n = 1–9) clusters with ethane

Abstract

Cost-effective and readily accessible 3d transition metals (TMs) have been considered as promising candidates for alkane activation while 3d TMs especially the early TMs are usually not very reactive with light alkanes. In this study, the reactivity of V_n⁺ and V_nO⁺ (n = 1–9) cluster cations towards ethane under thermal collision conditions has been investigated using mass spectrometry and density functional theory calculations. Among V_n⁺ (n = 1–9) clusters, only V_3–5⁺ can react with C₂H₆ to generate dehydrogenation products and the reaction rate constants are below 10⁻¹³ cm³ molecule⁻¹ s⁻¹. In contrast, the reaction rate constants for all V_nO⁺ (n = 1–9) with C₂H₆ significantly increase by about 2–4 orders of magnitude. Theoretical analysis evidences that the addition of ligand O affects the charge distribution of the metal centers, resulting in a significant increase in the cluster reactivity. The analysis of frontier orbitals indicates that the agostic interaction determines the size-dependent reactivity of V_nO⁺ cluster cations. This study provides a novel approach for improving the reactivity of early 3d TMs.