Structures and thermal decomposition of some diphenyllead bispolyfluorobenzoates

Abstract

The diphenyllead bispolyfluorobenzoates, Ph₂Pb(O₂CR)₂ (R = C₆F₅, p-MeOC₆F₄ or p-EtOC₆F₄), obtained from diphenyllead diacetate and the appropriate polyfluorobenzoic acids, are considered to have associated structures with bridging bidentate carboxylate groups in the solid state and to be predominantly monomeric with chelating carboxylate groups at low concentrations in chloroform. Thermal decomposition of Ph₂Pb(O₂CC₆F₅)₂ in boiling pyridine gave Ph₂Pb(C₆F₅)₂ and a low yield of Ph₃PbC₆F₅, whereas Ph₂Pb(O₂C-p-MeOC₆F₄)₂ and Ph₂Pb(O₂C-p-EtOC₆F₄)₂ gave low yields of Ph₃Pb-p-MeOC₆F₄ and Ph₂Pb(p-EtOC₆F₄)₂ respectively. From decomposition of Ph₂Pb(O₂CC₆F₅)₂ under vacuum, Ph₂Pb(C₆F₅)₂, Ph₃PbC₆F₅, Ph₄Pb, PhC₆F₅, (C₆F₅)₂CO and CO₂ were obtained, whilst Ph₄Pb, Ph₂, PhR, RCO₂Ph, R₂CO and CO₂ were detected from pyrolysis of Ph₂Pb(O₂CR)₂ (R= p-MeOC₆F₄ or p-EtOC₆F₄). These compounds are formed by competing decarboxylation, rearrangement, and (under vacuum) homolysis reactions of the diorganolead dicarboxylates, and by further reactions of the rearrangement products.