Directed syntheses and structural studies of mononuclear copper(II) and heterodinuclear copper(II)–iron(III) complexes from the same unsymmetrical dinucleating ligand‡

Abstract

Mononuclear copper(II) [Cu(H₃L)(O₂CMe)]BPh₄1 and heterodinuclear copper(II)–iron(III) [FeCuL(µOEt)]ClO₄2 complexes from the same dinucleating ligand H₃L have been prepared and isolated {H₃L = 2-[bis(2-hydroxybenzyl)aminomethyl]-4-methyl-6-[bis(2-pyridylmethyl)aminomethyl]phenol}. The crystal structure of the mononuclear complex 1 demonstrated the site-directed complexation with H₃L. For the heterodinuclear complex 2 the crystal structure reveals that the copper and iron atoms are bridged by the central phenoxo moiety and by an exogenous ethoxo group. In addition this structure showed that the iron atom is five-co-ordinated. Temperature-dependent magnetic susceptibility measurements revealed an antiferromagnetic interaction (ca.J = –58.1 cm^–1) between the copper and iron atoms in 2. Cyclic voltammograms in dichloromethane vs. Ag–AgNO₃ revealed a quasi-reversible redox behaviour for Cu^II–Cu^I in 1 and 2 (E_½ = –0.77 and –0.74 V respectively). The reduction of Fe^III in 2 is irreversible with E_pc = –1.69 V. The Cu^IFe^III complex is thermodynamically stable towards comproportionation.