THIOLATO TECHNETIUM COMPLEXES .5. SYNTHESIS, CHARACTERIZATION, AND ELECTROCHEMICAL PROPERTIES OF BIS(ORTHO-PHENYLENEBIS(DIMETHYLARSINE))TECHNETIUM(II) AND BIS(ORTHO-PHENYLENEBIS(DIMETHYLARSINE)) TECHNETIUM(III) COMPLEXES WITH THIOLATO LIGANDS - SINGLE-CRYSTAL STRUCTURAL-ANALYSES OF TRANS-[TC(SCH3)2(DIARS)2]PF6 AND TRANS-[TC(SC6H5)2(DIARS)2]0

Three different thiols have been brought into reaction with trans-[Tc(OH)(O)(DIARS)2]2+ to produce initially the Tc(II) complex, [Tc(SR)2(DIARS)2]0, which can be oxidized to the Tc(III) complex, [Tc(SR)2(DIARS)2]+ (DIARS = o-phenylenebis(dimethylarsine)). In the case of SR = SCH3 and SCH2C6H5, the Tc(II) and Tc(III) products were found to be in the trans geometry, while for SR = SC6H5, both cis and trans isomers were generated. Two of the complexes were structurally characterized by X-ray diffraction. trans-[Tc(SCH3)2(DIARS)2]PF6, chemical formula TcAs4S2PF6C22H38, crystallizes in the monoclinic space group C2/c, with Z = 4 and lattice parameters a = 20.440 (3) angstrom, b = 11.989 (2) angstrom, c = 13.284 (2) angstrom, beta = 98.24 (1)-degrees, and V = 3221.5 (7) angstrom 3. The final weighted R value is 0.026. The Tc atom occupies an inversion center. Important molecular parameters are Tc(III)-S = 2.292 (2) angstrom, Tc(III)-As = 2.496 (2) angstrom, S-C = 1.816 (7) angstrom, and Tc-S-C = 118.9 (2)-degrees. trans-[Tc(SC6H5)2(DIARS)2]0, chemical formula TcAs4S2C32H42, crystallizes in the monoclinic space group P2(1)/c with Z = 2 and lattice parameters a = 12.406 (2) angstrom, b = 14.924 (3) angstrom, c = 9.848 (2) angstrom, beta = 108.62 (2)-degrees, and V = 1727.9 (6) angstrom 3. The final weighted R value is 0.027. The Tc atom occupies an inversion center. Important molecular parameters are Tc(II)-S = 2.410 (2) angstrom, Tc(II)-As = 2.471 (2) angstrom, S-C = 1.794 (7) angstrom, and Tc-S-C = 119.5 (3)-degrees. Representative elemental analyses, FAB mass spectra, and visible-UV spectra are reported. Electrochemical and spectroelectrochemical measurements were taken on trans-[Tc(SCH3)2(DIARS)2]+, trans-[Tc(SCH2C6H5)2(DIARS)2]+, and cis-[Tc(SC6H5)2(DIARS)2]+, which exhibit a reversible Tc(III/II) redox couple in the range -0.32 to -0.47 V vs. Ag/AgCl. Another redox couple is present in the range -1.22 to -1.70 V; this is ascribed to Tc(II/I) and is reversible only for SR = SCH2C6H5 at 20-degrees-C. At room temperature, chemically irreversible couples are exhibited at ca. +1.0 V for Tc(IV/III).