Controlled Copper-Mediated Chlorination of Phenol Rings under Mild Conditions

• Published in: Inorganic chemistry Vol. 46; no. 12; pp. 4944 - 4950
• Main Authors: Song, Yu-Fei, van Albada, Gerard A, Tang, Jinkui, Mutikainen, Ilpo, Turpeinen, Urho, Massera, Chiara, Roubeau, Olivier, Costa, José Sanchez, Gamez, Patrick, Reedijk, Jan
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 11.06.2007
• Subjects: Chemical Sciences; Chlorine - chemistry; Copper - chemistry; Ligands; Magnetic Resonance Spectroscopy; Magnetics; Mass Spectrometry; Material chemistry; Molecular Structure; Phenols - chemistry; Water - chemistry; X-Ray Diffraction
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic070057n

The very unusual case of copper-mediated chlorination of phenol rings under mild conditions at room temperature is reported. Reaction of the ligand 1,7-bis(2-hydroxyphenyl)-2,6-diaza-4-hydroxylheptane (H3L1) with CuCl2 in acetonitrile leads to either the formation of a tetranuclear copper(II) complex [Cu4(HL3)2(μ-Cl)2Cl2](CH3CN) (1) or a linear trinuclear complex [Cu3(HL1)2Cl2(CH3CN)2](CH3CN)2 (2), depending on the reaction conditions. Both compounds have been fully characterized, including the determination of their 3D structures by X-ray diffraction. The unprecedented tetranuclear compound 1 is constituted of a dichlorido-bridged dimer of di-μ-phenoxido-dinuclear species, whereas the trinuclear complex 2 presents a linear array of copper(II) ions, held together through di-μ-phenoxido bridges of the central and external ions. The magnetic susceptibility of the two compounds was investigated, revealing either very strong (J < −500 cm-1) or strong (J value around −370(1) cm-1) antiferromagnetic dominant interactions among the CuII ions for 1 and 2, respectively. The tetranuclear complex 1 is obtained, under dry conditions, through the in situ formation of ligand HL3 (H3L3 = 1,7-bis(2-hydroxy-5-chlorophenyl)-2,6-diaza-4-hydroxylheptane) by oxidative chlorination of (HL1)2-. In the presence of traces of water, 1 is partially hydroxylated at the ortho position of one of the phenyl rings. The use of trimethylorthoformate as the dehydrating agent prevents the formation of hydroxylated ligands. Several partly chlorinated/hydroxylated products (identified as H3L2) have also been obtained through slight variations of the synthetic procedures (presence or absence of water and/or triethylamine in the reaction mixtures). These partially chlorinated and/or hydroxylated coordination species are mutually isomorphous to either 1 or 2. Several “modified” ligands have been isolated and characterized by 1H NMR and MS, after reaction with sodium sulfide of the complexes formed.