Ligands with Two Different Binding Sites and O2 Reactivity of their Copper(I) Complexes

The synthesis of two new unsymmetric dinucleating ligand systems, L1, combining a bidentate binding site with a tridentate binding site linked through a dibenzofuran spacer, and L2, with two tridentate binding sites bridged by an ethylene spacer, is reported. The ligands L1 and L2 were used for the preparation of the dicopper(I) complexes [Cu-2(L1)(NCCH3)(3)](X)(2), {[Cu-2(L1)Cl-2]}(n) and [Cu-2(L2)(NCCH3)(2)](Y)(2) (X = PF6, BF4, OTf; Y = ClO4, PF6, BF4), in which the two respective copper ions possess two different coordination environments. All complexes reacted with O-2, but in the case of the L1 series, no primary O-2 adduct could be identified by UV/Vis spectroscopy. Reaction of the [Cu-2(L2)(NCCH3)(2)](Y)(2) complexes with pure oxygen led to the formation of an O-2 adduct that proved rather unstable.