Knölker-Type Iron Complexes Bearing an N-Heterocyclic Carbene Ligand: Synthesis, Characterization, and Catalytic Dehydration of Primary Amides

A family of iron Knolker-type complexes bearing an N-heterocyclic carbene (NHC) ligand has been synthesized from the corresponding tricarbonyl(η4-cyclopentadienone)iron complex by reaction with the in situ generated NHC ligand, under UV irradn. (350 nm) at room temp. The six complexes, obtained in good yields (64-84%) after purifn. on column chromatog., were fully characterized, including X-ray diffraction and electrochem. studies. The activity of these complexes in catalysis has been demonstrated for the dehydration of primary benzamides into benzonitriles under hydrosilylation conditions using inexpensive polymethylhydrosiloxane (PMHS) as the hydrosilane at 100 °C.