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.