Mercury(II) complexes of sterically demanding arenechalcogenolato ligands, Hg(EC₆H₂R₃-2,4,6)₂(E = S or Se; R = Me, Prⁱ or Bu^t: E = Te; R = Me or Prⁱ) have been prepared. Whereas complexes carrying smaller aryl substituents (R = Me) are polymeric, those with R = Prⁱ and Bu^t form linear two-co-ordinate molecules. For a given R, the volatility of the complexes increases for E = S < Se < Te, while the thermal stability decreases in the same sequence. The preferred thermal decomposition pathway is reductive elimination to metallic mercury and the corresponding diaryl dichalcogenide. The oxidative addition of diaryl ditellurides to mercury and the reverse reaction are dependent on solvent polarity and steric factors; in the case of Te this leads to an unexpected decrease in stability with increased steric hindrance of the aryl substituents, R = Me > Prⁱ Bu^t.