Tungsten (VI) Complexes with 2-Hydroxy-5-chlorthiophenol in the Presence of Aminophenols and Their Application

In the present paper, we report results from liquid-liquid extraction-spectrophotometric experiments on 2 different systems, each of which containing W(VI), a 2-hydroxy-5-chlorothiophenol (H2L), and an - aminophenols (AP1,2) {As aminophenole 2(N, N-dimethylaminomethyl)-4-chlorphenol (АP1) and 2(N, N-dimethylaminomethyl)-4-bromphenol (AP2) were used}. In the complex formation with H2L, W (VI) is reduced to W (V) by the reagent itself. This fact was also confirmed by ESR spectrometry. Extraction of mixed ligand complexes is maximal at pH 4.1-5.2. The absorption maxima of the mixed-ligand complex (MLC) W(V)- L - AP1,2 lie in the range of 476-480 nm. Molar coefficients of absorption make (2.0-2.8)×104. The optimum amount of AP for the maximum binding of the anionic hydroxyl thiophenolate complex of tungsten [W (V)–L] into an ionic associate was determined by varying the quantity of AP added. For the formation of MLC W(V)-L- AP1,2, the concentration of 1.2 ×10-3 M of H2L and 2.0 × 10–3 M of AP1,2 in the solution is required. MLC of W(V)–L–AP1,2 were stable in aqueous and organic solvents and did not decompose for three days, and after extraction, more than a month. The maximum absorbance is reached within 5-8 minutes. Beer’s law is obeyed over the concentration range 0.10–18 W(V) μg mL-1. The method is free from common interferences. The proposed method were applied to the determination of tungsten in steel and samples of soil.