Synthesis, characterization and catalytic properties of multinuclear copper(II) complexes

Four tetranuclear [Cu4(O)(Ln)2(CH3COO)4] (1, 2, 4 and 5) and one pentanuclear [Cu5(OH)2(L3)2(CH3COO)6] (3) with N2O-donor Schiff-base ligands have been synthesized, where HL1 = 4-methyl-2,6-bis(2-hydroxyethyliminomethyl)phenol for complex 1, HL2 = 4-methyl-2,6-bis(3-hydroxypropyliminomethyl)phenol for complex 2, HL3 = 4-methyl-2,6-bis(4-hydroxybutyliminomethyl)phenol for complex 3, HL4 = 4-methyl-2,6-bis(5-hydroxypentyliminomethyl)phenol for complex 4 and HL5 = 4-methyl-2,6-bis(6-hydroxyhexyliminomethyl)phenol for complex 5. These complexes have been characterized by elemental analysis, FT-IR, UV–Vis spectroscopy. The structures of 1, 3, 4 and 5 have been determined by single crystal X-ray diffraction studies. X-ray analysis reveals that complexes 1, 4 and 5 are μ4-oxido-bridged tetrameric copper(II) complexes, where four copper atoms arrange themselves around an oxidooxygen atom at the vertices of a distorted tetrahedron. The pentanuclear complex, 3, has been found to have two μ3-hydroxido bridging ligands each connecting three copper atoms. These complexes have been employed as catalyst for the epoxidation of olefins in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant under mild conditions.

Graphical abstractFour tetranuclear copper(II) and a pentanuclear Cu(II) complexes with Schiff-base ligands have been synthesized and characterized using different methods. These complexes have employed as catalyst for the epoxidation of olefins using tert-butyl hydroperoxide as the oxidant.Figure optionsDownload full-size imageDownload as PowerPoint slide