COPPER THIOETHER CHEMISTRY - SYNTHESIS AND X-RAY CRYSTAL-STRUCTURES OF BINUCLEAR COPPER(I) COMPLEXES [CU2([24]ANES8)]2+, [CU2([28]ANES8)2+ INCORPORATING OCTATHIA MACROCYCLES

Reaction of L {L = ]24[aneS8, ]28[aneS8} with two molar equivalents of [Cu(NCMe)4]X(X- = ClO4-, BF4-, PF6-) in MeCN affords the white binuclear copper(I) complexes ]Cu2(L)[2+. A single crystal X-ray structure determination of ]Cu2(]24[aneS8)[ (BF4)2 shows two tetrahedron copper(I) centres, each of which is coordinated to four thioether sulphur-donors, Cu-S(1) = 2.263(3), Cu-S(4) = 2.363(3), Cu-S(7) = 2.349(3), Cu-S(10) = 2.261(3) angstrom. The Cu...Cu distance is 5.172(3) anstrom. A single crystal X-ray structure determination of [Cu2(CU2([28]aneS8)](ClO4)2 shows that this complex also contains two tetrahdral copper(I) centres, each coordinated to four thioether sulphur-donors, Cu-S(1) =2.278(5), Cu-S(4) = 2.333(5), Cu-S(8) = 2.328(5), Cu-S(11) = 2.268(5) angstrom. The Cu...Cu distance of 6.454(3) angstrom is greater than in [Cu2([24]aneS8)]2+, reflecting the greater cavity size in [Cu2([28]aneS8)]2+. Cyclic voltammetry of [Cu2([24]aneS8)]2+, reflecting the greater cavity size in {Cu2([28]aneS8)2+. Cyclic voltammetry of [Cu2([24]aneS8)]2+ and [Cu2([28]aneS8)]2+ at platinum electrodes in MeCN (0.1 M (n)Bu4NPF6) shows irreversible oxidations at e(pa) = + 0.88 V, +0.92 V vs Fc/Fc+, respectively, at a scan rate of 200 mV s-1. Coulometric measurements in MeCN confirm these oxidations to be two-electron (one electron per copper) processes to give binuclear copper9II) species. Oxidation of the binuclear copper(I) percursors with H2SO4 or HNO3 affords ESR-active copper(II) species which presumably incorporate SO4(2-) and NO3- bridges.