Crystal structures of μ-oxalato-bis-[azido-(hista-mine)-copper(II)] and μ-oxalato-bis-[(dicyan-amido)(hista-mine)-copper(II)

Chen Liu,Khalil A Abboud

doi:10.1107/s2056989015019908

Abstract

The title compounds, μ-oxalato-κ(4) O (1),O (2):O (1'),O (2')-bis-[[4-(2-amino-eth-yl)-1H-imid-azole-κ(2) N (3),N (4)](azido-κN (1))copper(II)], [Cu2(C2O4)(N3)2(C5H9N3)2], (I), and μ-ox-al-ato-κ(4) O (1),O (2):O (1'),O (2')-bis-[[4-(2-amino-eth-yl)-1H-imidazole-κ(2) N (3),N (4)](dicyanamido-κN (1))copper(II)], [Cu2(C2O4)(C2N3)2(C5H9N3)2], (II), are two oxalate-bridged dinuclear copper complexes. Each Cu(II) ion adopts a five-coordinate square-pyramidal coordination sphere where the basal N2O2 plane is formed by two O atoms of the oxalate ligand and two N atoms of a bidentate chelating histamine mol-ecule. The apical coordination site in compound (I) is occupied by a monodentate azide anion through one of its terminal N atoms. The apical coordination site in compound (II) is occupied by a monodentate dicyanamide anion through one of its terminal N atoms. The mol-ecules in both structures are centrosymmetric. In the crystals of compounds (I) and (II), the dinuclear complexes are linked through N-H⋯X and C-H⋯X (X = N, O) hydrogen bonds where the donors are provided by the histamine ligand and the acceptor atoms are provided by the azide, dicyanamide, and oxalate ligands. In compound (I), the coordinatively unsaturated copper ions inter-act with the histamine ligand via a C-H⋯Cu inter-action. The coordinatively unsaturated copper ions in compound (II) inter-act via a weak N⋯Cu inter-action with the dicyanamide ligand of a neighboring mol-ecule. The side chain of the histamine ligand is disordered over three sets of sites in (II).

Highlights

4](dicyanamido-N )copper(II)], [Cu2(C2O4)(C2N3)2(C5H9N3)2], (II), are two oxalate-bridged dinuclear copper complexes
Each CuII ion adopts a fivecoordinate square-pyramidal coordination sphere where the basal N2O2 plane is formed by two O atoms of the oxalate ligand and two N atoms of a bidentate chelating histamine molecule
Hydrogen bonds where the donors are provided by the histamine ligand and the acceptor atoms are provided by the azide, dicyanamide, and oxalate ligands

Summary

Chemical context

The oxalate ligand often plays an important role as a versatile bridging ligand in the formation of coordination polymers of various dimensionalities, including dinuclear complexes, chains, two-dimensional layered structures etc. (Coronado et al, 2003; Pardo et al, 2010). The oxalate ligand often plays an important role as a versatile bridging ligand in the formation of coordination polymers of various dimensionalities, including dinuclear complexes, chains, two-dimensional layered structures etc. In our effort to design and synthesize coordination polymers in a more rational and controlled fashion, we decided to use oxalate-based dinuclear complexes as molecular building blocks in preparing ladder-like coordination polymers. One strategy would be to introduce a linear bridging ligand to link the dinuclear units into ladder-like structures. Some potential choices of linear bridging ligands include azide and dicyanamide anions which have been widely used as bridging ligands in the design and synthesis of coordination polymers. The azide anion mainly coordinates in an end-on or end-to-end fashion (Escuer & Aromı, 2006; Stamatatos & Christou, 2009), while dicyanamide exhibits several different coordination modes (Batten & Murray, 2003). Complexes, we obtained the title compounds as dinuclear units interacting via hydrogen-bonding and weak interactions

Structural commentary

Supramolecular features

Synthesis and crystallization

Refinement details