A new unsymmetrical N,O-donor hexadentate ligand. Synthesis, structure and properties of its first vanadyl(IV) complex

Abstract

A new N,O-donor polyfunctional compound N-(2-hydroxybenzyl)-N′-(2-hydroxyethyl)-N,N′-bis(2-pyridylmethyl)-ethane-1,2-diamine (H₂bbpeten) and its first oxovanadium(IV) complex have been prepared in order to investigate the co-ordination chemistry of the unsymmetrical hexadentate ligand derived from an alkyldiamine containing phenolate-type, hydroxyethyl, and α-pyridyl pendant arms. The complex [V^IVO(Hbbpeten)]PF₆ 1 was characterized by elemental analyses, molar conductivity, IR, electronic and EPR spectroscopies, electrochemistry and X-ray diffraction methods. Spectroelectrochemistry in the UV/VIS spectral region has also been used to characterize the V^VO³⁺ analogue. The value E_½ = 0.427 V vs. ferrocenium–ferrocene obtained from spectropotentiostatic data is consistent with cyclovoltammetric results. The electronic spectrum of the oxidized species shows two intense LMCT transitions in the 350–550 nm range, and solutions of [V^VO(Hbbpeten)]²⁺ are stable on the time-scale of the experiments. A plot of E_½vs. number of co-ordinated phenolates for 1 and structurally related complexes shows a fairly linear trend.