Complexation of Tricarbonyltechnetium(I) Ion with Halide and Thiocyanate Ions in Aqueous Solution: 9 9 Tc NMR Study

Abstract

Complexation of the Tc(CO)3(H2O)3+ ion with halide (F-, Cl-, Br-, I-) and thiocyanate ions in aqueous solutions was studied by 99Tc NMR spectroscopy. The stability constants of the mono-, di-, and tri- substituted complexes were calculated. The stability of halide (Cl-, Br-, I-) complexes grows as the ionic radius of the halogen increases and its electronegativity decreases. For halide complexes of similar composi- tion, the 99Tc chemical shift correlates with the stability of the complexes. The fluoride ion, most probably, does not coordinate with the Tc(CO)3+ ion, in contrast to its close analog, hydroxide ion. Among the ligands studied, the pseudohalide anion NCS- forms the most stable complexes with the Tc(CO)3+ ion.