Models for thiophene hydrodesulfurisation

The reduction in sulfur dioxide emissions from petrochemical combustion remains a key requisite for adherence to the Montreal protocol. The majority of organosulfur compounds in crude petroleum are thiophene derivatives that may be reduced to hydrocarbons (hydrodesulfurisation) over molybdenum sulfide catalysts doped with a variety of late transition metals including ruthenium. Despite much effort directed towards understanding this heterogeneous process, the vast majority of model studies in homogeneous systems do not involve metal centres in a sulfur-rich coordination environment as would be found on the surface of these sulfided catalysts. We have, therefore, begun to explore the organometallic chemistry of thiophene when bound to hydrodesulfurisation-active metals in which a range of sulfur donors complete the coordination environment. The example shown involves a polydentate macrocycle that combines both a thiophene unit and three thioether donors. Notably, with only three coordination sites available at ruthenium, the thiophene coordinates in preference to one of the thioether groups, which remains pendant.