Solvent-free synthesis of bismuth thiolates and carboxylates

Abstract

The thermally induced solvent-free reactions of Ph₃Bi with a series of thiols and carboxylic acids (2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-ethoxybenzoic acid, 1-mercapto-2-propanol and salicylic acid) in the ratio 1 ∶ 3 have been investigated and shown to produce the fully substituted bismuth thiolates and benzoates in good yields and purity. Thermogravimetric analysis and differential scanning calorimetry have been used to study the profiles of those reactions involving two solid components and indicate that the reactions occur with the onset of the melting of Ph₃Bi. The two products from the reactions with 2-ethoxybenzoic acid and 1-mercapto-2-propanol have been characterised by single crystal X-ray diffraction and shown to be dimeric, [(2-EtOC₆H₅CO₂)₃Bi]₂, 1, and polymeric, [{(CH₃CH(OH)CH₂S)(CH₃CH(O)CH₂S)}Bi]_∞, 2, respectively. Compound 1 crystallises as centrosymmetric dimers with the two Bi centres bridged by carboxylate O atoms with possible polymerisation prevented by the further interaction of one of the ethoxy groups with each metal centre. In contrast compound 2 is made up of monomeric units, containing both a mono-anion and a dianion with quasi polymeric linkages arising from bridging S atoms accompanying OH⋯O hydrogen bonding interactions between the two ligand species.