Acid-catalysed hydrolysis of cis-[Cr(C2O4)(AaraNH2)(OH2)(OSO2)]? (where AaraNH2 denotes methyl 3-amino-2,3-dideoxy-α,d-arabino-hexopyranoside)

摘要

The synthesised complex cis-[Cr(C2O4)(AaraNH2)(OH2)(OSO2)]? anion with SO 3 2? as a ligand in the inner coordination sphere, where AaraNH2 denotes methyl 3-amino-2,3-dideoxy-α-d-arabino-hexopyranoside, was hydrolysed in the presence of acid at H+ concentrations from 0.01 to 2.7 m (HClO4). The reaction kinetics was studied with the stopped-flow spectrophotometric (u.v.–vis.) technique at temperatures of 5, 10, 15, 18 and 20 °C. This hydrolysis turned out to be a single-step process. Determined for this reaction were the rate constant k 1 for the removal of SO2 from the coordination sphere of the cis-[Cr(C2O4)(AaraNH2)(OH2)(OSO2)]? ion and the constant pK 1 of the protonation of this species in the reaction preceding the hydrolysis. The final product of this reaction – a new complex of CrIII, cis-[Cr(C2O4)(AaraNH2)(OH2)2]+, was obtained. A mechanism for the acid hydrolysis reaction is put forward based on the analysis of the rate constants obtained.