Ligands with Two Different Binding Sites and O 2 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)(NCCH 3 ) 3 ](X) 2 , {[Cu 2 (L1)Cl 2 ]} n and [Cu 2 (L2)(NCCH 3 ) 2 ](Y) 2 (X = PF 6 , BF 4 , OTf; Y = ClO 4 , PF 6 , BF 4 ), 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)(NCCH 3 ) 2 ](Y) 2 complexes with pure oxygen led to the formation of an O 2 adduct that proved rather unstable.