A Thermo‐ and Photo‐Switchable Ruthenium Initiator For Olefin Metathesis

A ruthenium carbene complex bearing azobenzene functionality is reported. The complex exists in the form of two isomers differing by the size of the chelate ring. Both isomers were isolated by applying kinetic or thermodynamic control during the synthesis and characterized by X‐ray diffraction analysis. The isomerization of the complex was studied by UV/Vis spectroscopy. The stable isomer was tested as a catalyst in olefin metathesis. The complex was activated at about 100 °C to promote ring‐closing and ring‐opening polymerization metathesis reactions. The activation took place also at room temperature under middle ultraviolet radiation.