Study on the complex-formation reaction of yttrium with para-methyl-chlorophosphonazo(CPApM)

Abstract

Yttrium forms with CPApM a 1:2 α-complex instantaneously in acidic medium. At pH∼5 (buffer solution), the α-complex is transformed to a β-complex with an absorption peak at 755 nm after standing. The transformation reaction is a first-order reaction. The rate constant and the apparent activation energy were found to be 9.67 × 10−1 min−1 and 52.3 kJ·mol−1 respectively. The mechanism of the reaction shows that the β-complex (Y:CPApM=2:4) is formed by combining two molecules of α-complex with the liberation of one proton.