Selenoether complexes of copper(II) - Synthesis, spectroscopy and structures

The red-brown copper(II) diselenoether complexes, [Cu (L-L)(2)][BF4](2) (L-L = MeSeCH2CH2SeMe, MeSeCH2CH2CH2SeMe or PhSeCH2CH2SePh) have been prepared from copper(II) fluoroborate and the ligands in anhydrous dichloromethane. Some new dithioether analogues are also described. The reaction of MeSeCH2CH2SeMe and copper(II) fluoroborate in ethanol led to an unstable dark green substance which appeared to contain both copper(I) and copper(II) and was formulated [Cu(MeSeCH2CH2SeMe)(2)] [BF4](x). The complexes were characterised by analysis, W-visible and e.p.r. spectroscopy, and magnetic measurements, and cyclic voltammetry has been used to probe the Cu (II)/ Cu(I) redox couples. The complexes are too unstable in solution to obtain crystals for an X-ray study, but structural data has been obtained for both the Cu(II) and Cu(I) complexes by copper K-edge EXAFS studies. Ditelluroethers reduce copper(II) salts to copper(I) complexes.