Formation of dihelicate and mononuclear complexes from ethane-bridged dimeric bipyridine or phenanthroline ligands with copper(I), cobalt(II), and iron(II) cations

The dimeric ethane-bridged ligands 1,2-bis(6{prime}-methyl-2,2{prime}-bipyridin-6-yl)ethane (1) and 1,2-bis(9-methyl-1,10-phenanthrolin-2-yl)ethane (2) form a double-stranded helicate by complexation with copper(I), yielding the dinuclear complexes (Cu{sub 2}(1){sub 2})(ClO{sub 4}){sub 2} (1a) and (Cu{sub 2}(2){sub 2})(ClO{sub 4}){sub 2} (2a). The double-helical structure, in which two ligands are wrapped around two copper (I) cations, has been assigned by {sup 1}H NMR studies and confirmed in the case of the dinuclear complex 1a by x-ray diffraction. The crystal structure for the complex C{sub 48}H{sub 44}O{sub 8}Cl{sub 2}Cu{sub 2} is reported. The copper cations, which are arranged in a distorted tetrahedral fashion, are separated by a distance of 5.926 (1) {angstrom}. The dinuclear copper complexes with ligands 1 and 2 are oxidized in a single reversible dielectronic wave at potentials somewhat higher than those of mononuclear analogues. Ligand 2 gives a mononuclear cobalt(II) species of octahedral geometry, which has been fully characterized by x-ray diffraction. The crystal structure for the complex C{sub 30}H{sub 22}N{sub 4}O{sub 6}F{sub 6}S{sub 2}Co is reported also. Ligand 3 (1,2-bis(5{prime} methyl-2,2{prime}-bipyridin-5-yl)ethane) leads to a triply bridged dinuclear iron species. 29 refs., 3 figs., 3 tabs.