Abstract
Abstract It was reported previously that metal ions such as Mg2+, Cr3+, Cu2+, Mn2+, and Ca2+ catalyzed selective P–O bond cleavage of P–O–S linkage in the methanolysis of phenyl phosphatosulfate (PPS), and in contrast, metal ions such as Zn2+, Fe3+, Al3+, and Be2+ promoted selective S–O bond cleavage.1) We have now found that Cd2+ catalyzes mixed cleavage of P–O and S–O bond in a ratio of 58 and 42%, respectively, in the methanolysis of PPS. The value of second-order-rate constant (k2) for Cd2+ catalyzed P–O bond cleavage satisfied the correlation between values of k2(P–O) and ionic radii of metal ions, but that for Cd2+ catalyzed S–O bond cleavage was considerably smaller than that expected from the rate correlation. The presence of chloride ion reduced the rate of Cd2+ catalyzed P–O bond cleavage to about one tenth of that in the absence of chloride ion, but inhibited completely the S–O bond cleavage catalyzed by Cd2+ or Zn2+. The kinetic studies suggested that the inhibition by chloride ion occurred with the formation of ternary (PPS·Cd2+·Cl−) and tetramerous (PPS·Zn2+·2Cl−) complexes of substrate, metal ion and chloride ion. On the basis of these results the selectivity of the metal ion in the site of bond cleavage was discussed.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call