Copper(I) complexes of pentatomic heterocyclic selone donors

Summary New complexes of copper(I) with some heterocyclic pentatomic rings, X·CH₂·CH₂·NR·CSe, where X=CH₂, NH, NMe, NEt, S and R=H, Me, Et, were prepared by reacting copper(II) chloride and bromide in MeOH. The stoichiometry of the complexes and the binding mode of the ligands have been discussed comparatively, together with those of the thione parents. It is noteworthy that the selone ligands with R=H (L) yield complexes of the type CuL_nY, (n=1,2 or 3; Y=Cl or Br) like the corresponding thione ones. On the contrary, when R=Me or Et, the selonic ligands (L) give complexes whose stoichiometries, Cu₂LY₂ and Cu₃L₂Y₃, differ from the thione homologues. The i.r. spectra of the complexes compared with those of the ligands support the coordinative bondvia selenium atom.