Bidentate guanidine ligands with ethylene spacer in copper-dioxygen chemistry: Structural characterization of bis(μ-hydroxo) dicopper complexes

► The syntheses of four new aliphatic guanidine-amine-hybrid ligands and the reaction of their Cu(I) complexes with molecular oxygen are reported. ► In case of ligand TMGdmae (L2) a bis(μ-oxo) dicopper(III) species is observed. ► The molecular structures of 10 bis(μ-hydroxo) dicopper complexes based on these ligands are described. ► [Cu2(μ-OH)2(DMEGdmae)2]I2 exhibits a Cu···Cu distance of 2.860(1) Å, which is one of the smallest observed for such compounds so far. ► The influence of the anion on the structure of the bis(μ-hydroxo) dicopper(II) unit in these complexes is analyzed.