Synthetic routes to lead(II) derivatives of aromatic 1,2-diols and orthoquinones

Article abstract of DOI:10.1016/S0020-1693(03)00057-4

Complexes of lead(II) of the type Pb(O₂R) where R is a substituted aromatic group, can be prepared by the direct electrochemical oxidation of a lead anode in a non-aqueous solution of the appropriate substituted catechol, R(OH)₂. The products, which are colourless, air-stable, insoluble materials, and presumably cross-linked in the solid state, can be oxidised to the corresponding lead(IV) derivatives by iodine or tetrahalogeno-o-quinones. The direct reaction of elemental lead with an o-quinone in refluxing hexane or toluene yielded identifiable products in only two cases; with 2,5-tert-butyl-1,2-benzoquinone, the corresponding lead(II) catecholate was obtained, while with phenanthrenequinone the semiquinonate Pb(PSQ^?)₂ was isolated. These latter reactions are shown by electron spin resonance spectroscopy to proceed via free radical intermediates, and the spectra are analysed to give information on the species present in the reaction media.