Churchill, M.R. and Rotella, F.J. (1979) Crystal Structure and Molecular Configuration of a Tetranuclear Copper(II) Complex Active as a Catalyst in the Oxidative Coupling of Phenols by Dioxygen: Cu4OCl6 (nmp)3(OH2···nmp) (nmp = N-methyl-2-pyrrolidinone). Inorganic Chemistry, 18, 853-860.
http://dx.doi.org/10.1021/ic50193a063

has been cited by the following article:

• TITLE: Synthesis and Characterization of Novel μ-Carbonato Tetranuclear Copper Complexes [(Pip)4nCu4X4(CO3)2] in Aprotic Media

  AUTHORS: Mohamed A. El-Sayed, Hoda A. Elwakeil, Ahmed H. Abdel Salam, Hemmat A. Elbadawy

  KEYWORDS: Complexes, Tetranuclear Cuban, Carbonato Bridge, Copper

  JOURNAL NAME: Open Journal of Inorganic Chemistry, Vol.6 No.1, January 15, 2016

  ABSTRACT: In this work, novel oxidative coupling complexes, [(Pip)4nCu4X4(CO3)2] (n = 1 or 2, X = Cl or Br, Pip = piperidine), are synthesized from the reaction of well characterized Lewis base [(Pip)4nCu4X4O2] with carbon dioxide as a Lewis acid in CH2Cl2. These carbonato-derivatives are isolated as stable solids. They are easily soluble in aprotic solvents as CH2Cl2or phNO2. Cryoscopic measurements support tetranuclear structure for all of them. Electronic spectra in the near infrared with high molecular absorptivity may be explained for tetranuclear cuban structure to fulfil 3 halo-ligands for each copper centre in [(Pip)4nCu4X4(CO3)2]. The EPR spectra for [(Pip)4nCu4X4(CO3)2] complexes are axial type of spectra (dx2-y2 G.S) suggesting elongated tetragonal distortion for all of them. Cyclic voltammograms for [(Pip)4nCu4X4(CO3)2] are irreversible in character. These tetranuclear carbonato complexes show catalytical activity. They initiate the oxidation of 2,6-dimethylphenol (DMP) to 3,3’,5,5’-tetramethyl-4,4’-diphenoquinone (DPQ).