Double end-on azido derivative of a tridentate (NNO) Schiff base dimeric copper(II) complex: synthesis, X-ray structure, magnetic property and catalytic effectiveness

Abstract

A dimeric copper(II) complex, bis{(2-[1-(aminoethylimino)ethyl]-phenoxo}-di-μ1,1-azido-dicopper(II), [Cu2(L)2(μ2-1,1-N3)2] (1) [L = 2-[1-(aminoethylimino)ethyl]-phenoxo ion], has been isolated using a self-assembly reaction using a 1:1:1 molar ratio of Cu(NO3)2·3H2O, HL and NaN3 in methanol at room temperature and characterized through X-ray diffraction analysis and spectroscopic studies. X-ray structural analysis reveals that 1 consists of two distinct dinuclear molecular units, where each copper(II) center in the individual dinuclear unit adopts a distorted square pyramidal geometry with a CuN4O chromophore ligated through a tridentate (NNO) Schiff base and two N atoms of two different bridging azides in µ1,1-mode. Two Cu(II) centers are linked through double µ2-1,1-N3 bridges to form the dinuclear unit [Cu2(L)2(μ2-1,1-N3)2]. In the crystalline state, the dinuclear units in 1 are associated through weak intermolecular N-H⋯O hydrogen bonds to afford a 2-D sheet structure viewed along the crystallographic a-axis. The small magnitude of the antiferromagnetic interaction (J = –0.45 cm−1) is a result of the long Cu···Cu separation (3.205(2) Å). The catalytic efficacy of 1 was studied in a series of solvents for the epoxidation of alkenes using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions.