µ-η1:η1-N,N-Imidazolidine-bridged Dicopper (II/III) complexes of a new dinucleating µ-Bis(tetradentate) schiff base ligand: synthesis, structural characterization, 1H NMR spectroscopy, and magnetic coupling

Abstract

The copper coordination chemistry of a new imidazolidine-based doubly bridging μ-bis(tetradentate) ligand, H3mhbai is studied. A new family of pentacoordinate dinuclear complexes of formula [CuII2(-mhbai)(-X)]·2 H2O (1–4) [X = OAc, NO3, Cl, S2COMe], where H3mhbai stands for 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-4-methyl-3-aza-but-3-enyl]-2-methyl-1,3-imidazolidine, were synthesized from the ligand, H3mhbai in air. The complex 1 was structurally characterized by X-ray crystallography. The μ-η1:η1-N,N'-imidazolidine bridging mode between two copper(ii) ions has been identified in this complex along with a nonhelical binding mode of the μ-bis(tetradentate) ligand. Variable temperature (2–300 K) magnetic susceptibility data of 1 show the presence of a weak antiferromagnetic exchange interaction between the two triply bridged magnetically isolated copper(ii) (S = 1/2) ions. The χmT values start to drop at temperature below 50 K, to reach a value of 0.55 cm3 K mol–1 at 2 K for a coupling constant value of J = –2.2 cm–1. The 1H NMR spectrum of the weakly coupled complex 1 shows a total of seventeen hyperfine shifted peaks, as expected from the idealized Cs symmetry of the compound, spread over a very large window of chemical shift, spanning about 130 ppm. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)