99Tc NMR study of complexation of [Tc(CO)3(H2O)3]+ with halide and thiocyanate ions in aqueous solutions

Abstract

Complexation of [Tc(CO)3(H2O)3]+ with halides (F−, Cl−, Br−, and I−) and thiocyanate anions in aqueous solutions was studied by 99Tc NMR spectroscopy. The stability constants of mono-, di-, and tri-substituted complexes were calculated. The stability of halide (Cl−, Br−, and I−) complexes increases with an increase in the ionic radius and with a decrease in the electronegativity of the halogen. The chemical shift of the halide complexes with the similar composition was correlated with their strength. Fluoride anion, unlike hydroxyl anion, is not co-ordinated to Tc(CO)3 +. Among the examined ligands, NCS− forms the strongest complex with [Tc(CO)3]+.