Stability constants and rate coefficients for decarboxylation of lanthanide oxalacetates

Abstract

Stability constants β₁₀₁ of ML and β₁₀₂ of ML₂(M = lanthanide, L = oxalacetate) for most of the series La to Yb have been calculated from the electromotive force values of a glass electrode–calomel electrode cell at I= 0.5 mol dm^–3 and 25 °C. Rate coefficients for decarboxylation, k_ML and k_ML2′ have been calculated from UV spectrophotometric data obtained at I= 0.5 mol dm^–3. The stability-constant values follow the usual pattern for moderately strong complexes, i.e. increasing from La to Yb with a slight dip around Gd and Ho, but this pattern is not found in the rate coefficients. Those for k_ML decrease from Ce to Eu, rise again for Gd and Ho and then decrease again from Ho to Yb. The ratio of k_ML2 to k_ML is about 2 to 3:1 except for La, Ce and Yb. With La and Ce the k_ML2 values, like the β₁₀₂ values, are zero or very small while the ratio for the strong ytterbium complex is about 10:1. Some interpretations for the above trends are made.