Copper thioether chemistry: Synthesis and X-ray crystal structures of binuclear copper(I) complexes [Cu 2(L)] 2+ {L = [24]aneS 8, [28]aneS 8} 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) Å. The Cu … Cu distance is 5.172(3) Å. 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) Å. The Cu … Cu distance of 6.454(3) Å 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 nBU 4NPF 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 2SO 4 or HNO 3 affords ESR-active copper(II) species which presumably incorporate SO 4 2− and NO 3 − bridges.