Spectrophotometric study of the complexation equilibria and the determination of palladium(II) with 4-(5′-methyl-3′-isoxazolylazo)-resorcinol

Abstract

The complexation equilibria between PdII and 4-(5′-methyl-3′-isoxazolylazo)-resorcinol (MIAR) have been studied and the existence of the species PdH2R2+, PdHR+, PdR and PdOHR− have been established; the acid dissociation constants for the first three are pK121a = 2.65±0.16, pK111a = 7.09±0.15 and pK101a = 9.57±0.20. The ternary complex PdII-MIAR-hexamine has also been studied. A new method for the determination of 0.4–4.0 ppm Pd (ε = 1.8 x 104 1 Mol−1 cm−1) has been developed and applied to samples of hydrogenation catalysts.