A NEW UNSYMMETRICAL N,O-DONOR HEXADENTATE LIGAND - SYNTHESIS, STRUCTURE AND PROPERTIES OF ITS FIRST VANADYL(IV) COMPLEX

A new N,O-donor polyfunctional compound thyl)-N,N'-bis(2-pyridylmethyl )-ethane-1,a-diamine (H(2)bbpeten) and its first oxovanadium(rv) compl ex have been prepared in order to;investigate the co-ordination chemis try of the unsymmetrical hexadentate ligand derived from an alkyldiami ne containing phenolate-type, hydroxyethyl, and alpha-pyridyl pendant arms. The complex [(VO)-O-IV(Hbbpeten)]PF6 1 was characterized by elem ental analyses, molar conductivity, IR, electronic and EPR spectroscop ies, electrochemistry and X-ray diffraction methods. Spectroelectroche mistry in the UV/VIS spectral region has also been used to characteriz e the (VO3+)-O-V analogue. The value E-1/2 = 0.427 V vs. ferrocenium-f errocene obtained from spectropotentiostatic data is consistent with c yclovoltammetric results. The electronic spectrum of the oxidized spec ies shows two intense LMCT transitions in the 350-550 nm range, and so lutions of [(VO)-O-V(Hbbpeten)](2+) are stable on the time-scale of th e experiments. A plot of E-1/2 vs. number of co-ordinated phenolates f or I and structurally related complexes shows a fairly linear trend.