SYNTHETIC, STRUCTURAL, AND PHYSICAL STUDIES ON HEXATHIA-18-CROWN-6 AND ITS TRANSITION METAL COMPLEXES (THIOETHER, MACROCYCLE, COPPER, NICKEL, COBALT)

Hexathia-18-crown-6 (18s6) has been synthesized, characterized by x-ray diffraction, and found to be the first reported example of a macrocyclic thioether containing sulfur atoms with lone pairs pointing into the center of the ring. Analysis of the conformation of hexathia-18-crown-6 and other published crown ethers and crown thioethers suggests that the conformation of a crown can be predicted using the following gauche preference rules: C-S-C-C > C-C-C-O > C-C-O-C > C-C-C-S.; The nickel(II) complexes of (18s6) and trithianonane have been synthesized and characterized by electronic and NMR spectroscopy, magnetic methods, and x-ray diffraction. The cavity size of 18s6 is slightly smaller than the ionic radii of octahedral Ni(II), resulting in a complex with unusually short nickel-thioether bond distances. The compression of the Ni(II) ion by 18s6 is maintained in solution as shown by the larger ligand field strength of 18s6 than that of trithianonane in the analogous hexakis(thioether) Ni(II)bis(trithianonane) ('2+) cation.; The Co(II) complexes of 18s6 and trithianonane have been synthesized and characterized by electronic spectroscopy, EPR, electrochemistry, magnetic methods, and x-ray diffraction. Both complexes are unusual examples of octahedral, low spin Co(II) ions. Although 18s6 does compress the axial Co-S bonds, the low spin behavior is found to be a result of the polarizability of the thioethers and not primarily a result of the crown ligand. The polarizability of the thioethers also results in a very high Co(III)/Co(II) potential.; The Cu(II) and Cu(I) complexes of 18s6 have been synthesized, characterized by electrochemistry, EPR, and x-ray diffraction, and found to be the two halves of a high potential couple. Electrochemically reversible behavior is observed despite the difference in stereochemistry between the 6-coordinate octahedral Cu(II) complex and the 4-coordinate distorted-tetrahedral Cu(I) complex.; The Mn(IV) tris complexes of catecholate and 3,5-di-t-butylcatecholate have been synthesized. Characterization of these complexes by electronic spectroscopy, EPR, magnetic methods, electrochemistry, and x-ray diffraction establish that they are better formulated as Mn(IV)tris(catecholate) than Mn(III)bis(catecholate)(semiquinone).