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()] (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 []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.