Binuclear dioxomolybdenum(Vl) complexes of dithio- or methylene-bridged schiff bases^†

Abstract

The flexibly-bridged hexadentate tetraanionic ligands, L^4- [LH₄ = schiff base derived from the condensation of methylene- or dithiobis(salicylaldehyde) with benzoylhydrazide or <i>p</i>-nitrobenzoylhydrazide] and their binuclear dioxomolybdenum(VI) complexes have been synthesized and characterized by elemental analyses, molar conductance, IR, NMR and electrometric studies. The isolated complexes have an oligomeric structure, [(MoO₂)₂L]_n in which each molybdenum achieves a pseduo-octahedral structure via Mo<img src='http://www.niscair.res.in/jinfo/threedot.gif' border=0>O -> Mo bridging. The complexes accept neutral donor molecules (D) like pyridine, 4-methylpyridine, imidazole, etc., through their sixth labile binding site available in both [MoO₂]²⁺ units and form [(MoO₂)₂L(D)₂]. The cyclic voltammetric measurements indicate irreversible to quasireversible reduction of the molybdenum(VI) complexes to molybdenum(lV) with a cathodic reduction potential of - 0.83 to - 0.85 V vs SCE at the scan rate of 200 mV/ s.