Formation of Hybrid Guanidine‐Stabilized Bis(μ‐oxo)dicopper Cores in Solution: Electronic and Steric Perturbations

Abstract

A series of new hybrid peralkylated-amine-guanidine ligands based on a 1,3-propanediamine backbone and their Cu-O₂ chemistry is reported. The copper(I) complexes react readily with O₂ at low temperatures in aprotic solvents with weakly coordinating anions to form exclusively bis(μ-oxo) dicopper species (<b>O</b>). Variation of the substituents on each side of the hybrid bidentate ligand highlights that less sterically demanding amine and guanidine substituents increase not only the thermal stability of the formed <b>O</b> cores but enhance inner-sphere phenolate hydroxylation pathways. TD-DFT analysis on selected guanidine-amine <b>O</b> species suggest that the additional visible feature observed is a guanidine π*→ Cu₂O₂ LMCT, which appears along with the classic oxo-ζ_u*→Cu(III) and π_ζ*→ Cu(III) LMCT transitions.