CD-113 NUCLEAR-MAGNETIC-RESONANCE STUDIES OF CADMIUM(II)CARBOXYLATE COMPLEXES IN AQUEOUS-SOLUTION

A variety of complexes of cadmium with mono- and di-carboxylic acids i n aqueous solution were investigated using Cd-113 NMR spectroscopy. A single averaged chemical shift was obtained even at reduced temperatur e, showing that the cadmium-monocarboxylate complexes are undergoing r apid exchange in solution. Using the known stability constants, the in dividual chemical shifts were calculated to be in the range delta -22 to -24 and -39 to -40 for [CdL](+) and [CdL(2)] (L = carboxylate) spec ies respectively: carboxylates with higher basicity tend to increase t he shielding of the cadmium in the complexes. Tn case of dicarboxylic acids HO2C(CH2)(n)CO2H (n = 0-3) the Cd-113 nucleus showed greater shi elding with increasing n. The upheld chemical shift observed for the d ialkyl-substituted malonate complexes of Cd-II compared to the malonat e complex is caused by the steric effect hindering ring formation.