Studies on the co-colour reaction of platinum(IV) and palladium(II) with 4,4′-bis(dimethylamino)thiobenzophenone

Abstract

The sensitive co-colour reaction of Pt^IV and Pd^II with 4,4′-bis(dimethylamino)thiobenzophenone (TMK) in the presence of ascorbic acid and Triton X-100 was investigated. The effect of pH on the absorbance of the complex was studied using an acetic acid-sodium acetate buffer, the optimum pH range being between 2.8 and 4.5, in the presence of ascorbic acid and Triton X-100. The orange-red complex exhibits an absorption maximum at 530 nm with a molar absorptivity of 1.96 × 10⁵ dm³ mol^–1 cm^–1 for Pd^II(in the presence of 10 µg of Pt^IV) and 2.98 × 10⁵ dm³ mol^–1 cm^–1 for Pt^IV(in the presence of 10 µg of Pd^II). The Pt : Pd : TMK ratio in the complex was found to be 1 : 2 : 12. Beer's law is obeyed over the concentration range 0–0.8 ppm of Pd^II and 0–0.48 ppm of Pt^IV in the presence of 10 µg of Pt^IV and 10 µg of Pd^II, respectively. The optimum conditions for the co-colour reaction of Pt^IV and Pd^II with TMK and the interferences of foreign ions are reported. The proposed method has been used successfully for the spectrophotometric determination of platinum and palladium in synthetic samples. Based on the experiments, the structure of the complex and the mechanism of the co-colour reaction are proposed and discussed.