ChemInform Abstract: Aliphatic Amino Acid‐Metal Ion‐Aromatic Amine Ternary Complexes. Crystal Structures of Aqua(L‐leucinato)(1,10‐phenanthroline)copper(II) Nitrate and Aqua(DL‐leucinato)(1,10‐phenanthroline)copper(II) Nitrate

Abstract

Abstract The crystal structures of the two aliphatic amino acid-metal ion-aromatic diamine ternary complexes, [Cu( L -Leu)( o -phen)(H 2 O)]NO 3 (1) and [Cu( DL -Leu)( o -phen) (H 2 O)]NO 3 (2) (Leu=leucinato and o -phen=1,10-phenanthroline), have been determined by X-ray diffraction. Complex 1 crystallizes in the triclinic space group P 1 with a =12.362(2), b =11.593(2), c =7.311(2) A, α=107.82(2), β=76.05(2), γ=93.62(2)°, Z =2, D calc =1.557 g cm −3 , and R =0.045 for 3184 unique observed reflections. Complex 2 crystallizes in triclinic space group P 1 with a =12.368(4), b =11.608(4), c =7.280(3) A, α=107.16(3), β=75.98(3), γ=93.54(3)°, Z =2, D calc =1.556 g cm −3 , and R =0.052 for 2579 unique observed reflections. The L -Leu complex (1) involves two crystallographically independent molecules, which are related by a pseudo center of symmetry except for the C β atoms. Both the 1 and 2 structures are essentially identical, including the crystal packing mode, except for the existence of an exact crystallographic center of symmetry in 2. In 2 the C β atom of Leu is disordered at two positions corresponding to D - and L -configurations, respectively. In each complex, the copper atom is coordinated in a distorted squarepyramidal geometry by the bidentate Leu and o -phen ligands at the equatorial sites and water at an axial position. The isopropyl side chain of each Leu extends away from the aromatic ring system of o -phen, thus there is no intramolecular ligand-ligand interaction between them, in contrast to a ring-aliphatic hydrophobic interaction in solution for this ternary system. Factors affecting the formation of a folded structure having such an interligand interaction are considered from the structural viewpoint.