The aromaticity of tungstenacyclobutadiene, Cl3W(–ButC–CMe–CMe–): A DFT/NICS study

B3LYP and MP2 are used to investigate the geometry and aromaticity of tungstenacyclobutadiene, Cl3W(–ButC–CMe–CMe–). Nucleus-independent chemical shift is used as an index of aromaticity for this experimentally observed metallacyclobutadiene. Additionally, charge effects are explored by characterizing the aromaticity of the tungstenacyclobutadiene fragment ions, View the MathML sourceWC3H3+3 and View the MathML sourceWC3H3+1. CMO-NICS analysis provides the contribution of each B3LYP orbital to the aromaticity and allows differentiation between orbitals of σ and π symmetries.