Synthesis and characterization of mono- and μ6-sulfato hexanuclear zinc complexes of a new symmetric dinucleating ligand

Abstract

Zinc complexes of a new symmetric dinucleating ligand, N,N′-Bis[2-carboxybenzomethyl]-N,N′-Bis[carboxymethyl]-1,3-diaminopropan-2-ol (H₅ccdp) with mixed donating groups, have been studied in the solid state as well as in solution. In methanol, the reaction of stoichiometric and substoichiometric amounts of Zn(ClO₄)₂·6H₂O and the ligand H₅ccdp, in the presence of K₂CO₃ or Et₃N, afforded a mononuclear zinc complex, [Zn(H₂O)₆][Zn(H₂ccdp)(H₂O)₂]₂·12H₂O (1). The solid state structure of 1 contains two units of the zinc-ligand anion, [Zn(H₂ccdp)(H₂O)₂]⁻, and one [Zn(H₂O)₆]²⁺ counter cation. The Zn(II) center of the anion is in a distorted octahedral geometry. However, in methanol, the reaction of ZnSO₄·7H₂O and the ligand H₅ccdp in the presence of NaOH afforded a unique μ₆-sulfato hexanuclear zinc complex, Na₆[Zn₆(ccdp)₃(μ₆-SO₄)](OH)·10.5H₂O (2). The structure of 2 contains a [Zn^II₆(μ₆-SO₄)] core unit which is held together by three heptadentate bridging ligands, ccdp⁵⁻. Three of the Zn(II) centers are in highly distorted square pyramidal geometry, the other three Zn(II) centers are in a distorted octahedral geometry.