A new type of mu4-Oxo-bridged copper tetramer: synthesis, X-ray molecular structure, magnetism and spectral properties of (mu4-Oxo)tetrakis(mu-bromo)bis(mu-2, 6-bis(morpholinomethyl)-4-methylphenolato)tetracopper(II) and (mu4-Oxo)tetrakis(mu-benzoato)bis(mu-2, 6-bis(morpholinomethyl)-4-methylphenolato)tetracopper(II)

CuBr2 and sodium benzoate react with 2, 6-bis(morpholinomethyl)-4-methylphenol (Hbmmk) yielding two novel mu4-oxo-bridged tetranuclear copper(II) complexes. X-ray crystallography, magnetic measurements and NMR techniques reveal the molecular structure, magnetic properties and spectra properties of the complexes, respectively. The Cu(II) cluster complexes are the first members of this class to have chelating ligands.