A DFT Quantum‐Chemical Study of the Structure of Precursors and Active Sites of Catalyst Based on 2,6‐Bis(imino)pyridyl Fe(II) Complexes

Summary: A DFT method has been applied for quantum‐chemical calculations of the molecular structure of charge‐neutral complex LFeMe(μMe) 2 AlMe 2 which is formed in system LFeMe 2  + AlMe 3 (L = 2,6‐bis(imino)pyridyl). Calculations suggested the formation of highly polarized complex LFeMe(μMe) 2 AlMe 2 ( II ) in system LFeMe 2  + AlMe 3 , characterized by r (FeμMe) = 3.70 Å and r (AlμMe) = 2.08 Å and deficient electron density on fragment [LFeMe] Q ( Q  = +0.80 e). Polarization of the complex progresses with the bounding of two AlMe 3 molecules (complex LFeMe(μMe) 2 AlMe 2  · 2AlMe 3 ( III )) and with replacement of AlMe 3 by MeAlCl 2 (complex LFeMe(μMe) 2 AlCl 2 ( IV )). The activation energy of ethylene insertion into the FeMe bond of these complexes has been calculated. It was found that the heat of π ‐complex formation increases with increasing of polarization extent in the order II  <  III  <  IV . Activation energy of the insertion of coordinated ethylene into FeMe bond decreases in the same order: II  >  III  >  IV .Calculated model complex (NH 3 ) 3 FeMe 2 ; tridentate bis(imino)pyridyl ligand was substituted by three coplanar NH 3 groups.