Knölker complex

The Knölker complex is an organoiron compound, which is a catalyst for transfer hydrogenation. The complex features an hydroxycyclopentadienyl ligand bound to an Fe(CO)₂H centre. It is generated by the corresponding cyclopentadienone tricarbonyl by treatment with base followed by acidification. The compound is related to the organoruthenium compound called Shvo's complex, a hydroxycyclopentadienyl derivative that also functions as a catalyst for hydrogenation.