THIOLATO-TECHNETIUM COMPLEXES .4. SYNTHESIS, CHARACTERIZATION AND ELECTROCHEMICAL PROPERTIES OF BIS(1,2-BIS(DIMETHYLPHOSPHINO)-ETHANE)TECHNETIUM(III) COMPLEXES WITH ARENE-THIOLATO LIGANDS

The reaction of trans-[TcV(OH)(O)(DMPE)2]2+ (DMPE = 1,2-bis(dimethylphosphino)ethane) with a series of arenethiols in base produces the novel complexes cis-[Tc(III)-(SC6H4X-P)2 (DMPE)2]+ for X = H, Cl, Me, OMe, t-Bu. One of the complexes has been characterized by X-ray crystallography: cis-[Tc(SPh)2(DMPE)2]PF6, chemical formula Tc1S2P5F6C24H42, crystallizes in the orthorhombic space group P2(1)nb with Z = 4 and lattice parameters a = 9.311(1)angstrom, b = 11.190(2)angstrom, c = 31.936(4)angstrom, Vol = 3327.3(8) angstrom3. The final weighted R-value was 0.033. Averaged structural parameters are Tc-S = 2.29(2)angstrom, Tc-P (trans to P)=2.42(1)angstrom, Tc-P (trans to S) = 2.49(3)angstrom, Tc-S-C = 118.5(5)-degrees. The complexes have been characterized by FAB mass spectrometry and u.v.vis. spectroscopy. The visible region charge transfer bands are diagnostic for cis geometry in the [Tc(SR)2(DMPE)2]+ complexes. Electrochemical and spectroelectrochemical measurements show reversible Tc(III/II) redox couples in the range -0.19 V to -0.38 V versus Ag/AgCl (3 M NaCl). Irreversible couples are exhibited at ca. -1.1 V to -1.2 V for Tc(II/I) and +0.7 V to +0.9 V for Tc(IV/III). Variation in redox potential is discussed in terms of sulphur nucleophilicity.