Heterometallic Cu/Co and Cu/Co/Zn Complexes Bearing Rare Asymmetric Tetranuclear Cores: Synthesis, Structures, and Magnetic and Catalytic Properties Toward the Peroxidative Oxidation of Cycloalkanes

The three novel heterometallic complexes [CuCoIIICoII2(MeDea)3Cl3(CH3OH)0.55(H2O)0.45](H2O)0.45 (1), [CuCoIIIZn2(MeDea)3Cl3(CH3OH)0.74(H2O)0.26](H2O)0.26 (2), and [CuCoIIIZn2(MeDea)3Cl3(DMF)] (3) have been prepared using a one-pot reaction of copper powder with cobalt chloride (1) and zinc nitrate (2, 3) in a methanol (1, 2) or dimethylformamide (3) solution of N-methyldiethanolamine. A search of the Cambridge Structural Database shows that the tetranuclear asymmetric cores M4(μ3-X)(μ-X)5 of 1–3 represent an extremely rare case of M4X6 arrays. The magnetic investigations of 1 disclose antiferromagnetic coupling in a CoII–CuII–CoII exchange fragment with JCo–Cu/hc = –4.76 cm–1, JCo–Co/hc = –2.76 cm–1, and DCo/hc = +34.3 cm–1. Compounds 1–3 act as precursors for the mild peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone with overall yields up to 23%. The synthetic and structural features as well as the thermogravimetric behavior and electrospray ionization mass spectrometry data are discussed.