Rüdiger W. Seidel

On the Chiral Z′ = 2 Crystal Structure of [Cu2(H2valdien)2](NO3)2 [H2valdien = N1,N3-bis(3-methoxysalicylidene)diethylenetriamine]

AbstractThe crystal and molecular structure of [Cu2(H2valdien)2](NO3)2 (1), whereby H2valdien is the known Schiff base ligand N1,N3-bis(3-methoxysalicylidene)diethylenetriamine, is reported. In 1, two H2valdien ligands join two CuII ions in a chelate–spacer–chelate mode, in which the protonated aliphatic secondary amine moieties represent the spacers, to form a double helix. Both CuII ions in the homodinuclear cationic complex exhibit similar distorted square-planar N2O2 coordination spheres. The axially chiral molecular structure of the [Cu2(H2valdien)2]2+ complex features intramolecular π···π stacking and N–H⋯O hydrogen bonds in the crystal. Compound 1 crystallizes in the Sohncke space group P21, with a = 14.165(3), b = 13.7755(13), c = 21.1185(4) Å, β = 102.199(4)°, and with two enantiomeric molecules in the asymmetric unit (Z′ = 2). The two crystallographically unique [Cu2(H2valdien)2]2+ enantiomers are related by pseudo inversion symmetry.Graphical AbstractThe pseudo centrosymmetric chiral Z′ = 2 crystal structure (space group P21) of [Cu2(H2valdien)2](NO3)2, whereby H2valdien is the known Schiff base ligand N1,N3-bis(3-methoxysalicylidene)diethylenetriamine, is reported.

Adiponitrile at 100 K

Adiponitrile, C6H8N2, is a key intermediate in the synthesis of the polyamide Nylon 66 and is produced industrially on a large scale. We have determined the crystal and molecular structure of adiponitrile by single-crystal X-ray analysis at 100 K, a suitable crystal (m.p. 275 K) having been grown from the melt at low temperature. The compound crystallizes in the monoclinic space group P21/c with Z = 2. In the crystal structure, the molecule adopts an exact Ci-symmetric gauche-anti-gauche conformation of the C-C-C-C skeleton about an inversion centre. The molecules are densely packed, with short intermolecular contacts between the α-H and nitrile N atoms.

Acetic anhydride at 100 K: the first crystal structure determination

Acetic anhydride (ethanoic anhydride), (CH3CO)2O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single-crystal X-ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X-ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C2-symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.

Crystal structure of {6,6'-dihy-droxy-2,2'-[imino-bis-(propane-1,3-diyl-nitrilo-methanylyl-idene)]diphenolato-κ(5) O (1),N,N',N'',O (1')}copper(II).

The title compound, [Cu(C20H23N3O4)], crystallizes in the space group Cc with two independent molecules in the asymmetric unit. The CuII atoms are each coordinated by the pentadentate Schiff base ligand in a distorted trigonal bipyramidal N3O2 geometry. The equatorial plane is formed by the two phenolic O atoms and the amine N atom, while the axial positions are occupied by the two imine N atoms. In the crystal, the two independent molecules are each connected into a column along the b axis through intermolecular O—H⋯O hydrogen bonds. The two independent columns are further linked through an N—H⋯O hydrogen bond, forming a double-column structure.

Crystal structure of {2-[({2-[(2-amino­ethyl)amino]­ethyl}imino)­meth­yl]-6-hy­droxy­phenolato-κ4N,N′,N′′,O1}(nitrato-κO)copper(II) ethanol 0.25-solvate

In the crystal structure of the title mononuclear CuII complex, [Cu(C11H16N3O2)(NO3)]·0.25C2H5OH, the complex molecules are linked by N—H⋯O and O—H⋯O hydrogen bonds, forming a dimer with an approximate non-crystallographic twofold rotation axis of symmetry. In the monomeric unit, the Cu2+ ion exhibits a distorted square-pyramidal configuration, whereby the anionic [HL]− Schiff base ligand binds in a tetradentate fashion via the O and the three N atoms which all are approximately coplanar. The O atom of a nitrate anion occupies the fifth coordination site, causing the CuII atom to move slightly out of the approximate basal plane toward the bound nitrate group. The structure exhibits disorder of the ethanol solvent molecule.