Aerobic Oxidative Coupling of 2‑Naphthol Derivatives Catalyzed by a Hexanuclear Bis(μ-hydroxo)copper(II) Catalyst

A novel hexanuclear bis­(μ-hydroxo)­copper­(II)
complex, [L3(Cu2(μ-OH)2)3]­(ClO4)6 (1), was synthesized
with dinucleating ligand N,N,N,N-tetra­(pyridin-2-ylmethyl)-m-xylene diamine (L). Complex 1 is fully
characterized by X-ray crystallography and magnetic susceptibility
in the solid state and UV–vis and electron paramagnetic resonance
spectroscopy in solution. The molecular structure of 1 possesses three dicopper cores, in which two copper centers are
bridged by two hydroxide groups and separated by a distance ranging
from 2.8852(15) to 2.8937(10) Å. In addition, the three dicopper
cores are linked by the dinucleating ligand between each pair of adjacent
dicopper cores. Importantly, aerobic oxidative coupling of 2,4-di-tert-butylphenol, 2-naphthol, and six 2-naphthol derivatives
was achieved in 33–96% yield using complex 1 as
a catalyst.