Adducts of Triangular Silver(I) 3,5-Bis(trifluoromethyl)pyrazolate with Thiophene-Derivatives: A Weak Interaction Model of Desulfurization

The π-acidic triangular silver(I) 3,5-bis(trifluoromethyl)pyrazolate (Ag3pz3) has been employed to form air-stable 1:1 adducts with the so-called heterocyclic aromatic sulfur compounds (HASC), such as dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (DMDBT), benzothiophene (BT) and 2,5-dimethylthiophene (DMT), which are difficult to be removed from liquid fuels by hydrodesulfurization. Based on X-ray diffraction data, these adducts are stabilized by weak Ag⋯S contacts, Ag⋯C contacts and sometimes π-π stacking, which therefore may represent a kind of weak interaction model for some adsorptive desulfurization processes where metals play a vital role. Both experimental observation and DFT calculation suggest an order of combining intensity as: Ag3pz3·DBT ≈ Ag3pz3·DMDBT > Ag3pz3·BT > Ag3pz3·DMT.