Synthesis, crystal structure and esterification of a novel iron(III) 18-metallacrown-6 complex

Abstract

The trianionic heptadentate ligand, ( Z)-3-(5′-chlorosalicylhydrazinocarbonyl) propenoic acid, has been synthesized and reacted with FeCl 3·6H 2O, to produce the complex [Fe III 6(C 12H 8N 2O 5Cl) 6(H 2O) 4(CH 3OH) 2]·8H 2O·4CH 3OH. In the self-assembly process the ligand was esterified and transferred into ( Z)-methyl 3-(5′-chlorosalicylhydrazinocarbonyl) propenoate. In the crystal structure, the neutral Fe(III) complex contain a 18-membered metallacrown ring consisting of six Fe(III) and six trianionic ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Fe(III)–N–N]. Due to the meridional coordination of the ligands to the Fe 3+ ions, the ligands enforce the stereochemistry of the Fe 3+ ions as a propeller configuration with alternating Λ/Δ forms. The metallacrown can be treated with SnCl 2 or Zn powder to obtain purified ester.