SYNTHESIS AND CHARACTERIZATION OF NITRIDO TC(V) AND RE(V) COMPLEXES WITH FERROCENEDITHIOCARBOXYLATE (FCCS(2)=[FE(C5H4CS2)(C5H5)](-))

The first mixed technetium-iron complexes [Tc-99g(N)(FcCS(2))(2)] (FcC S(2) = [Fe-II(C5H5)(C5H4CS2)](-)) (1) and [Tc-99g(N)(FcCS(2))(FcCS(2) )](+) (FcCS(2) = [Fe-II(C5H5)(C5H4CS2)](-); FcCS(2) = Fe-III(C5H5)(C5 H4CS)) (2) have been prepared and characterized. Complex 1 was obtaine d by reaction of the precursor complex [(TC)-T-99g(N)Cl-2(PPh3)(2)] wi th the piperidinium salt of the ligand FcCS(2). The resulting biferroc ene complex is formed by two FcCS(2) ligands bound to the Te atom thro ugh the four sulfur atoms of the two CS2- groups and bridged by a Tc=N multiple bond. The mixed-valence Fe2+-Fe3+, monocationic complex 2 wa s isolated as secondary product of the reaction of the precursor compl ex [(TC)-T-99g(N)Cl-4](-) with the ligand FcCS(2). It has the same com position as 1 except for the fact that the Fe(II) center of one FcCS(2 ) ligand has been oxidized to Fe(III). The electrochemical properties of 1 and 2 are consistent with their formulations. Cyclic voltammetric studies and controlled potential electrolyses showed that complex 1 u ndergoes a quasi-reversible. two-electron exchange at 0.320 V (vs ferr ocene/ferrocenium couple) attributed to the oxidation of the two Fe(II ) ions, while complex 2 undergoes a quasi-reversible, one-electron exc hange at nearly the same potential (0.344 V) assigned to the oxidation of the residual Fe(II) ion. These results indicate that in complex 1 the two Fe(II) atoms behave as independent redox centers. The synthesi s, characterization, and electrochemical behavior of the analogous, si x-coordinated rhenium(V) complex [Re(N)(FcCS(2))(2)(PPh3)] are also re ported.