Monometallic and heterobimetallic complexes derived from salen-type ligands

Mononuclear and heterodinuclear complexes of the salen-type ligand H2LH2 [H2LH2 = 2,2′-[1,2-dihydroxybenzene-4,5-diylbis(nitrilomethylidine)]bis(3,5-di-tert-butylphenol)] were prepared, whereof [{Mn(CH3OH)2}LH2]Cl, [ML(ZrCp2∗)] (M = Ni, Cu, CrCl(py); py = pyridine, Cp∗ = pentamethylcyclopentadienyl) were characterized by X-ray analysis. Additionally, cyclic voltammetric investigations were performed to ascertain the influence of the second transition metal complex fragment [ZrCp2∗]2+ on the metallo salen ligand. Moreover, the complexes were tested in the catalytic epoxidation of styrene. Although the complexes are quite sensitive towards oxidants, monometallic complex [{Mn(CH3OH)2}LH2]Cl exhibited a conversion of 70.6% with styrene oxide selectivity of 88% over 1 h at room temperature.

Graphical abstractMono- and heterometallic complexes of the salen-type ligand H2LH2 2,2′-[1,2-dihydroxybenzene-4,5-diylbis(nitrilomethylidine)]bis(3,5-di-tert-butylphenol) were applied in catalytic oxidation reactions. The manganese complex [{Mn(CH3OH)2}LH2]Cl showed the highest activity.Figure optionsDownload full-size imageDownload as PowerPoint slide