A family of oxorhenium(v) complexes incorporating chelated monoanionic ONN reduced Schiff base and dianionic ONNO tetradentate ligands: synthesis, spectroscopic and electrochemical studies

Abstract

The green colored complexes of the type Re^VO(L_SB)Cl₂, 1, have been synthesised by reacting NBu₄[ReOCl₄] with HL_SB in dry ethanol. Here, L_SB⁻ are the deprotonated forms of N-(2-hydroxybenzyl)-2-picolylamine (HL_SB¹); N-(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine (HL_SB²) and N-(2-hydroxybenzyl)-N′,N′-diethylethylenediamine (HL_SB³). Similarly, NBu₄[ReOCl₄] reacted with N,N-bis(2-hydroxybenzyl)-2-picolylamine (H₂L¹); N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine (H₂L²); N,N-bis(2-hydroxybenzyl)-N′,N′-diethylethylenediamine (H₂L³); {N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)}-2-aminoethanol (H₂L⁴); {N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)}-2-methyl-2-amino-1-propanol (H₂L⁵); N,N-bis(1-hydroxyethyl)-2-picolylamine (H₂L⁶), to give the monochloro complexes Re^VO(L)Cl, 2. The X-ray structures of the complexes are reported. The molecular structures observed in the solid state are preserved in solution (¹H NMR). In acetonitrile solution the Re^VO(L)Cl, 2, display a one-electron couple, Re^VIO(L)Cl⁺–Re^VO(L)Cl, near 1.0 V vs SCE. The electrogenerated hexavalent complexes [Re^VIO(L)Cl]ClO₄, 3, are paramagnetic and display sextet EPR spectra in solution at room temperature (A_av ∼ 417 (G), g ∼ 1.914).