Three naphthalene-based analogues (4 a-c) of the Hoveyda-Grubbsmetathesiscatalyst exhibited immense differences in reactivity. Systematic structural and spectroscopic studies revealed that the ruthenafurane ring present in all 2-isopropoxyarylidene chelates possesses some aromatic character, which inhibits catalystactivity. This aromatic stabilization within the chelate ring may be controlled by