Synthesis and characterization of technetium(III) complexes with nitrogen heterocycles by oxygen atom transfer from oxotechnetium(V) cores. Crystal structures of mer-[Cl3(pic)3Tc] and mer-[Cl3(pic)(PMe2Ph)2Tc] (pic = 4-picoline). Electrochemical parameters for the reduction of TcII, TcIII, and TcIV

Abstract

The combination of pyridine ligands, (OCl{sub 4}Tc){sup {minus}}, and O atom acceptors of different cone angles, such as PMe{sub 2}Ph or PPh{sub 3}, results in Tc{sup III} complexes that vary in the coordination of the phosphine ligand. The compounds mer(Cl{sub 3}(4-picoline){sub 3}Tc) and mer-(Cl{sub 3}(4-picoline)(PMe{sub 2}Ph){sub 2}Tc) have been obtained in good yield and have been characterized spectroscopically and by single-crystal x-ray diffraction. The crystal structure data are reported. Linear correlations of technetium reduction potentials in DMF with electrochemical ligand additivity parameters (E{sub L}'s) have been obtained for the Tc{sup II,I}, Tc{sup III,II}, and Tc{sup IV,III} couples. The slope and intercept (S{sub M}, I{sub M}) pairs for each technetium oxidation-reduction couple, respectively, are (1.39, {minus}2.07), (1.29, {minus}0.91), and (1.00, 0.65). 32 refs., 3 figs., 6 tabs.