Copper(II) complexes of aliphatic tridentate amine/dithioether ligands – Synthesis and molecular structures

Three new tridentate ligands (1–3) featuring a central secondary amine linked by ethylene bridges to two thioether donor functions with S-methyl or S-benzyl substituents have been synthesized and reacted with copper(II) chloride or copper(II) nitrate. The resulting complexes of type [CuX2(L)] (L = amine-dithioether ligand) 6, 7, and 9 exhibit a square-pyramidal coordination geometry with the nitrogen and sulfur donor groups of the tridentate ligand occupying three of the basal binding sites at the metal ion. Two chloro (6 and 7) or a nitrato ligand (9) originating from the metal precursor salt complete the coordination sphere of the copper(II) ion. The apical donors are bonded with significantly longer bond distances compared to identical donors in the basal plane. The weakly bound apical chloro ligand of 6 can be abstracted with silver(I) nitrate effecting the formation of the dinuclear complex 10 featuring a nitrato ligand coordinated to two copper(II) centers in a bridging fashion. For all copper(II) complexes the observed Cu–S bond distances are very similar and not significantly influenced by alteration of the alkyl group at the thioether donor function.