Synthetic and structural comparisons of bismuth(III) carboxylates synthesised under solvent-free and reflux conditions

Two synthetic approaches to the formation of bismuth(III) carboxylates have been explored and compared. Ph3Bi was reacted with a series of carboxylic acids (RCO2H) of varying pK(a) and functionality (R = PhCH= CH, o-MeOC6H4, m-MeOC6H4, o-H2NC6H, o-O2NC6H4, p-O2NC6H4, 2-(C5H4N)) under reflux conditions in toluene and solvent-free. The thermochemical profiles of the solvent-free reactions were also studied by DSC-TGA. All reactions produced the tri-substituted bismuth carboxylates in comparable yields and purity with the exceptions of picolinic acid and p-nitrobenzoic acid. 2-Picolinic acid exclusively formed the di-substituted complex, [PhBi(2-(C5H4N)CO2)(2)](4), by both methods, while p-nitrobenzoic acid gave the tri-substituted complex through reflux and the di-substituted complex under solvent-free conditions. Two of the complexes were structurally authenticated by single crystal X-ray diffraction: [ PhBi(2-(C5H4N) CO2)(2)](4) is tetrameric formed through five membered chelate rings involving the pyridyl N and O(-C) rather than the less stable carboxylate (- CO2) chelates, while [Bi(o-MeOC6H4CO2)(3)](infinity), is a polymer in which dimeric units, constructed around two chelating and one unsymmetrical bridging carboxylate on each Bi centre, are then joined together through longer intermolecular Bi - O bridging bonds.