Copper thioether chemistry: Synthesis and X-ray crystal structures of binuclear copper(I) complexes [Cu2(L)]2+ {L = [24]aneS8, [28]aneS8} incorporating octathia macrocycles ☆

Abstract Reaction of L {L = [24]aneS 8 , [28]aneS 8 } with two molar equivalents of [Cu(NCMe) 4 ]X (X − = ClO 4 − , BF 4 − , PF 6 − ) in MeCN affords the white binuclear copper(I) complexes [Cu 2 (L)] 2+ . A single crystal X-ray structure determination of [CU 2 ([24]aneS 8 )](BF 4 ) 2 shows two tetrahedral 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) A. The Cu … Cu distance is 5.172(3) A. A single crystal X-ray structure determination Of [CU 2 ([28]aneS 8 )](ClO 4 ) 2 shows that this complex also contain two tetrahedral 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) A. The Cu … Cu distance of 6.454(3) A is greater than in [CU 2 ([24]aneS 8 )] 2+ , reflecting the greater cavity size in [CU 2 ([28]aneS 8 )] 2+ . Cyclic voltammetry of [CU 2 ([24]aneS 8 )] 2+ and [CU 2 ([28]aneS 8 )] 2+ at platinum electrodes in MeCN (0.1 M n BU 4 NPF 6 ) 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 copper(II) species. Oxidation of the binuclear copper(I) precursors with H 2 SO 4 or HNO 3 affords ESR-active copper(II) species which presumably incorporate SO 4 2− and NO 3 − bridges.