Molybdate-hydroxylamine reaction: Synthesis, characterisation and electrochemistry of Mo(NO)<img src='http://www.niscair.res.in/jinfo/twoplustwo.gif' border=0>, Mo(NO)²⁺ and Mo(NO)(NH₂O)²⁺ chelates with 8-quinolinol

Abstract

The reaction of MoO<img src='http://www.niscair.res.in/jinfo/four1.gif' border=0> and NH₂OH.HCl with 8-quinolinol (QOH) gives an orange yellow solid from which complexes [Mo(NO)₂(QO)₂] (1), [MoO₂(QO)₂] (2), [Mo(NO)₂(QO)₂] (3) and [Mo(NO)₂(QO)₂] (4) are obtained on repeated solvent extraction followed by column chromatography. The complex [Mo(NO)₂(QO)₂] contains two magnetically non-equivalent QO ligands in a seven coordinate pentagonal bipyramidal arrangement. The complex [Mo(NO)(QO)₂] is paramagnetic, showing axially symmetric EPR signals (<i>g</i>_⊥ =2.02, g_ll=2.00) and super hyperfine splitting (S H F S), caused by the ¹⁵N of the equatorial and equivalent QO ligands. The electronic spectrum of the chelate also supports the suggested gross structure. The compound [Mo(NO)₂(QO)₂] shows a stepwise two-electron reduction of the Mo(NO)<img src='http://www.niscair.res.in/jinfo/twoplustwo.gif' border=0> moiety but the reverse oxidation occurs in a single step, the cyclic response being pseudo-reversible with respect to the first reduction wave. Interestingly, [Mo(NO)₂(QO)₂] under aerobic conditions, induces electropolymerisation causing the deposition of a conducting polymer [poly-8-quinolinol, as evidenced by IR spectral data], on the working platinum foil electrode.