Infrared, X-ray and microscopic studies on the room temperature structure of anhydrous lead (II) n-alkanoates

The room temperature structures of a series of even-chain length lead (II) n-alkanoates have been studied using infrared spectroscopy, X-ray diffraction and polarizing light microscopy. Whilst the bonding is the same for both long and short chain compounds, where four carboxylate groups form an unsymmetrical bidentate bond with a lead atom, with possible carboxylate bridging to adjacent lead atoms, at least for the short chain length compounds, the arrangement of hydrocarbon chains within a lamella is different. Both X-ray and microscopic studies show that for short chain compounds, hydrocarbon chains are arranged as bilayers within a lamella and tilted with respect to the lead basal plane. For the long chain compounds, it is proposed that the chains are arranged as a monolayer within a lamella, in an alternating arrangement, and slightly tilted with respect to the lead basal plane. For all the compounds, X-ray data point to a triclinic unit cell containing four molecules per unit cell with P1¯ symmetry, and chains oriented along the c axis.