CROWN THIOETHER CHEMISTRY. THE Co(II) COMPLEXES OF HEXATHIA-18-CROWN-6 AND BIS(TRITHIANONANE)

Article abstract of DOI:10.1021/ja00266a015

The cobalt(II) complexes of hexathia-18-crown-6 (18S6) and 2,5,8-trithianonane (ttn) have been synthesized and characterized by electron paramagnetic resonance, electrochemical, magnetic, and X-ray diffraction methods. (picrate)2 crystallizes in the triclinic system, space group P1/, with a = 6.659(2) Angstroem, b = 9.565(3) Angstroem and c = 13.591(4) Angstroem, α = 85.15(2)deg, β = 76.05(2)deg, and γ = 76.08(2)deg, and Z = 1. (BF4)2 crystallizes in the orthorhombic system, space group P2₁2₁2₁, with a = 10.321(5) Angstroem, b = 12.181(5) Angstroem, c = 21.522(14) Angstroem, and Z = 4.In both complexes the cobalt ion is coordinated solely by thioether groups to give bona fide low-spin six-coordinate Co(II) complexes both in the solid state and solution.Consistent with the low-spin formulation, the complexes exhibit S = 1/2 magnetic moments, and EPR spectra with g_<*> ca. 2, g_<*> >/= 2, and their CoS₆ coordination spheres display marked Jahn-Teller elongation.In addition, cyclic voltammetric measurements show that the complexes exhibit extraordinarly high potentials for the Co(III/II) couple (>/= +840 mV vs.NHE).These results emphasize the ability of thioether ligands to stabilize low-spin and oxidation states by virtue of their ? acidity.