Synthese und Koordinationsverhalten neuer Schiffscher Basen aus 3-Formylacetylaceton und natürlichenL-Aminosäuren

Abstract

Three novel chiral Schiff Base ligands (H2L) were prepared from the condensation reaction of 3-formyl acetylacetone with the amino acids L-alanine, L-phenylalanine, and L-threonine. X-ray single crystal analyses revealed that the Schiff Base compounds exist as enamine tautomers in the solid state. The molecular structure of the compounds is stabilized by an intramolecular hydrogen bridge between the enamine NH function and a carbonyl oxygen atom of the pentandione residue. Treatment of the ligands H2L with copper(II) actetate in the presence of pyridine led to the formation of copper complexes [CuL(py)]. In each of the complexes the copper atoms adopt a distorted square-pyramidal coordination. Three of the basal coordination sites are occupied by the doubly deprotonated Schiff Bases L2– which act as tridentate chelating O, N, O-ligands. The remaining coordination sites are occupied by a pyridine ligand at the base and a carboxyl oxygen atom of a neighboring complex at the apical position. The latter coordination is responsible for a catenation of the complexes in the solid state.