RESUMO
The first diiron(iii,iv)-µ2-oxo tetracarbene complex is isolated and characterized by SC-XRD, UV/Vis, EPR, Evans' NMR and elemental analysis. CV indicates the presence of a transient high-valent diiron(iv)-µ2-oxo species. Its formation and decay is investigated via UV/Vis kinetics and NMR.
Assuntos
Materiais Biomiméticos/química , Complexos de Coordenação/química , Enzimas/metabolismo , Ferro/química , Metano/análogos & derivados , Cinética , Metano/química , Modelos Moleculares , Conformação MolecularRESUMO
The synthesis of trans axially substituted mono- (1 a) and bis(tert-butylisocyanide) (1 b) derivatives of the highly active homogeneous bio-inspired iron(II) olefin epoxidation (pre-)catalyst 1 bearing an equatorial macrocyclic tetra N-heterocyclic carbene and two trans axial labile acetonitrile ligands is reported. NMR spectroscopy and SC-XRD indicate a considerable π-backdonation from the iron(II) centres to the isocyanide ligand(s). The impact of isocyanide substitution on the electronic features of the complexes is studied by cyclic voltammetry revealing a significant increase in half-cell potential assignable to the reversible Fe(II)/Fe(III) redox couple with an increasing number of isocyanides as a result of their π-accepting properties: E1/2 =0.15â V (1), E1/2 =0.35â V (1 a), E1/2 =0.44â V (1 b).