THIOLATO TECHNETIUM COMPLEXES .6. SYNTHESIS, CHARACTERIZATION, ELECTROCHEMICAL PROPERTIES AND CRYSTAL-STRUCTURE OF [TC(TDT)(DMPE)2]PF6 [TDT=TOLUENE-3,4-DITHIOLATE, DMPE=1,2-BIS(DIMETHYLPHOSPHINO)ETHANE]

The technetium(V) complex [Tc(OH)O(dmpe)2]2+ can be reduced by excess of toluene-3,4-dithiol (H-2tdt) to yield the technetium(III) complex [Tc(tdt)(dmpe)2]PF6. The product has been characterized by elemental analysis, UV/VIS spectroscopy, fast atom bombardment mass spectrometry and X-ray crystallography. It crystallizes in the triclinic space group P1BAR with Z = 2, a = 9.1508(9), b = 12.794(2), c = 13.516(2) angstrom, alpha = 93.94(1), beta = 95.24(1) and gamma = 108.791(9)-degrees. The final R value was 0.037. The technetium co-ordination geometry is midway between octahedral and trigonal prismatic. Relevant structural parameters are Tc-S 2.318(6), S-C 1.738(4) angstrom, S-Tc-S bite angle 84.49(4)-degrees and Tc-P 2.402(7) angstrom. The entire tdt ligand is planar. Electrochemical and spectroelectrochemical measurements have been made for the reversible Tc(III)-Tc(II) and Tc(II)-Tc(I) couples at -0.600 and -1.217 V respectively vs. Ag-AgCl (3 mol dm-3 NaCl). A quasi-reversible Tc(IV)-Tc(III) couple was observed at +0.680 V. The properties of [Tc(tdt)(dmpe)2]PF6 are compared to those observed previously for related cis- and trans-[Tc(SR)2(dmpe)2]+/0 (R = alkyl or aryl) complexes.