Cyclopentadienone Iron Complexes Research Articles

Design, Synthesis and Catalytic Activity of (Cyclopentadienone)iron Complexes Containing a Stereogenic Plane and a Stereogenic Axis.

Herein, we report the synthesis and characterization of several chiral (cyclopentadienone)iron complexes (CICs) featuring either two (R)-BINOL-derived stereoaxes or a combination of one (R)-BINOL-derived stereoaxis and a stereogenic plane. The stereoplane-containing CICs were obtained as epimer mixtures, which were separated by flash column chromatography and assigned an absolute configuration based on XRD analysis, NMR and order of elution. The library was tested in the asymmetric hydrogenation of ketones showing good catalytic activity and a moderate stereoselectivity which, notably, is mostly imparted by the stereogenic plane. Indeed, the two epimers of each CIC possessing a stereoplane show opposite and equally strong stereochemical preference.

Recent Catalytic Applications of (Cyclopentadienone)iron Complexes

(Cyclopentadienone)iron complexes (CICs) are attractive pre‐catalysts due to their easy preparation and robustness, which are uncommon features in homogeneous iron catalysis. They represent a striking example of how deeply a non‐innocent ligand may affect the catalytic properties of the metal. Swinging between the cyclopentadienone and the hydroxycyclopentadienyl form, the ligand induces iron to engage in H2 heterolytic cleavage and transfer. The latter represents the basis for numerous applications of CICs in redox chemistry (multiple bond reduction, alcohol oxidation) and “hydrogen borrowing” processes (e.g., alcohol amination) that have been reported over the last few years. Moreover, very recently catalytic applications of CICs in different types of reactivity (where again the non‐innocent ligand plays a key role), have appeared in the literature. This minireview summarizes the advancements that have been made in the field of CICs and their catalytic applications in the period 2014–2019.

Cyclopentadienone iron complexes as efficient and selective catalysts for the electroreduction of CO2 to CO

Robust and easy-to-synthesize cyclopentadienone iron(0) complexes selectively catalyze the electrochemical conversion of CO2 to CO. Cooperation between the metal center and the coordinated organic ligand is a key factor for activity of these novel electrocatalysts.

Insight into the Mechanism of Dihydrogen‐Heterolysis at Cyclopentadienone Iron Complexes and Subsequent CX Hydrogenation

AbstractA bifunctional iron‐based catalyst (7), a compound related to the [Fe]‐ or Hmd‐hydrogenase, was studied by using experimental and computational methods. Catalyst 7 bears a protic hydrogen atom at the ligand and a hydridic hydrogen atom at the iron atom, which originate from the heterolytic uptake of H2, and can be transferred to unsaturated molecules (i.e. carbonyl compounds and imines). Our DFT calculations indicate that a non‐classical dihydrogen‐iron complex exists, and that the hydrogen uptake is an exergonic process. The hydrogenation of carbonyl compounds proceeds through a synchronous, concerted outer‐sphere mechanism, whereas the hydrogenation of the imine 18 is a two‐step process. In the first step, the imine is protonated to afford an iminium ion, to which the hydride is then transferred in a second reaction step. Energy hypersurfaces were calculated by using a solvent (toluene) continuum model.