Copper(II)–Mercury(II) Heterometallic Complexes Derived from a Salen-Type Ligand: A New Coordination Mode of the Old Schiff Base Ligand

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 H2L-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.