A computational study of carbene ligand stabilization of biomimetic models of the rotated Hred state of [FeFe]-hydrogenase

Stabilization of fully rotated conformation at one of the iron center has been achieved for the reduced Fe(I)Fe(I) state in chelated cyclic alkyl amino carbene (CAAC) substituted biomimetic hydrogenase model complex. This study indicates that the spatial orientation of the chelated NHCs at one of the iron center plays a major role in determining the geometry at the other iron center. We also made an attempt at explaining the electronic origin behind the favorability of rotated vs unrotated structure in asymmetrically substituted chelated vs monodentate NHC complexes.