Effect of the coordination of compounds containing nitrogen and sulfur donor atoms to lead(II) bis(N,N-diethyldithiocarbamate) on the inhibition of initiated ethylbenzene oxidation

The inhibiting activity of thirteen nitrogen and sulfur compounds (ligands, L) in the presence of lead(II) diethyldithiocarbamate (Pb(dtc)₂) (1: 1) in the initiated oxidation of ethylbenzene with oxygen at 75°C was studied. Six ligands and Pb(dtc)₂ inhibit ethylbenzene oxidation when used individually. The joint use of antioxidants in two out of thirteen cases leads to the enhancement of the inhibiting activity of a pair as compared to that predicted by the rule of mixtures. The formation of new lead(II) complexes ([Pb(dtc)₂ L]) was revealed in ethylbenzene, chloroform, and acetonitrile solutions by UV-visible spectrophotometry and anodic polarography for all the L + Pb(dtc)₂ pairs due to the coordination of a ligand donor atom to the metal. In the cases of enhancement of the antioxidant activity of the ligands when they were used in combination with Pd(dtc)₂ (1: 1), the specificity of the ligand structure was established. This is very important for the selection of inhibiting ligand + metal complex pairs. The tentative structure and parameters of the chelate center of the [Pb(dtc)₂ L RO^· ₂] were given.