Tuning the Bonding of a μ-Mesityl Ligand on Dicopper(I) through a Proton-Responsive Expanded PNNP Pincer Ligand

Abstract

We report the synthesis and characterization of a series of cationic, neutral, and anionic dicopper(I) complexes featuring a μ-mesityl ligand and a naphthyridine-derived PNNP expanded pincer ligand. Structural characterization showed that the protonation state of the dinucleating ligand has a pronounced effect on the bending and tilting of the μ-mesityl ligand. DFT calculations indicate that the varying orientations of the μ-mesityl ligand are inherent due to changes in electronic structure rather than crystal-packing effects. NBO analysis reveals how the interactions that contribute to the three-center–two-electron bond between the μ-mesityl ligand and the dicopper core change for the various degrees of observed bending and tilting.