Copper(II)–mercury (II) heterometallic complexes derived from a salen-type ligand: a new coordination mode of the old Schiff base ligand

Abstract

Three heterometallic copper (II)–mercury (II) complexes, [(CuL-CH₃)HgCl₂] (1), [(CuL-CH₃)₂HgCl₂] (2) and [(CuL-CH₂]-HgCl) ₂] (3), have been synthesized by reacting the “complex as ligand” [CuL-CH₃] with HgCl₂ by varying the reaction conditions and stoichiometry of the reactants, where H₂]L-CH₃ = the di-Schiff base of 1,3-propanediamine and 2-hydroxyacetophenone. All three complexes have been characterized by X-ray single-crystal structure, elemental and spectroscopic analyses. In complex 1, the Hg (II) ion is bonded by two phenoxido oxygen atoms of a [CuL-CH₃] moiety and two terminal chloride ions to form a dinuclear species. In the trinuclear complex 2, the central Hg (II) ion is coordinated by two terminal [CuL-CH₃] units through one phenoxido oxygen from each unit and two chloride ions. On the other hand, in the tetranuclear complex 3, the Hg (II) ion has a distorted-tetrahedral geometry, being bonded to one chloride, two phenoxido oxygen atoms of one [CuL–CH₂]- unit and a methyl carbon atom of another [CuL–CH₂]- unit. The structure of complex 3 reveals an unprecedented heptadentate coordination mode (1-κ⁴NN′OO′:2-κ²OO′:3-κC) of the Schiff base ligand that resulted in a unique organomercury metallamacrocycle.