Crystal structure of dichlorido{2-methyl-2-[(pyridin-2-ylmethyl)amino]propan-1-ol-κ3 N,N′,O}copper(II) from synchrotron data

The CuII ion in the title compound shows a distorted square-pyramidal coordination geometry with two N and one O atoms of the mpmapOH ligand and two Cl anions. In the crystal, molecules are connected by hydrogen bonds and π–π interactions, forming a strong supramolecular network along the a-axis direction.


Chemical context
Polyamine ligands have attracted much interest in the development of coordination and bio-inorganic chemistry because they can easily bind or interact with transition metal ions and form stable multifunctional metal complexes with significant potential applications in catalysis (Ahn et al., 2016), magnetic materials (Benelli et al., 2013) as well as pharmacology (Stringer et al., 2015). For example, various platinum complexes including polyamine ligands or their derivatives have been synthesized and investigated as potential anticancer agents, e. g. nedaplatin, heptaplatin, and lobaplatin (Kapdi & Fairlamb, 2014). In particular, polyamine derivatives containing hydroxyl groups can easily form various multinuclear metal complexes and supramolecular compounds because the hydroxyl groups can be fully or partially deprotonated and act as hydrogen-bonding donors and/or acceptors. For example, bpaeOH [bpaeOH = N,N-bis(2-pyridinmethyl)-2-aminoethanol] and H 2 pmide [H 2 pmide = N-(2-pyridylmethyl)iminodiethanol] ligands containing pyridine, amine and hydroxyl groups have been used to form multinuclear iron(III) complexes (Shin et al., 2014) and mixed-valence cobalt(II/III) complexes and have shown significant magnetic interactions and catalytic activities toward various olefins and alcohols (Shin et al., 2011). Chloride ions in such complexes can easily bridge two metal ions, allowing the assembly of supramolecular compounds (Sabounchei et al., 2015).

Structural commentary
In the title compound (I) (Fig. 1), the copper(II) ion is fivecoordinated by two nitrogen and one oxygen atoms from the mpmapOH ligand and by two chloride anions. The coordination geometry around the copper ion can be described as distorted square-pyramidal. The equatorial plane consists of the two nitrogen (N1 and N2) atoms and the hydroxyl group (O1) of the mpmapOH ligand and one chloride anion (Cl1). The coordination geometry is completed by an axial coordination of the second chloride anion (Cl2). The chloride anions coordinate in a cis position to each other. The Cu-L mpmapOH bond lengths are in the range 1.9881 (10) to 2.0409 (9) Å . The Cu-Cl bond lengths are 2.2448 (5), and 2.5014 (6) Å , respectively, with the larger value corresponding to the axial chloride ligand. The equatorial atom Cl1 lies 0.332 (1) Å above the equatorial plane, away from the axial chloride anion Cl2. The bite angles of the five-membered chelate rings involving C5, C6 and C7, C10 atoms are 82.92 (4) and 82.97 (4) , respectively. The bond angles around the copper ion range from 82.92 (4) to 161.51 (4) .

Supramolecular features
The two chloride anions form strong intermolecular hydrogen bonds with secondary amine and hydroxyl groups of adjacent mpmapOH ligands, giving rise to a polymeric chain along the b axis ( Fig. 2 and Table 1) (Steed & Atwood, 2009). The hydrogen-bonded polymeric chains are linked by face-to-face interactions between the pyridine groups of the mpmapOH ligand with a centroid-to-centroid distance of 3.764 (1) Å and an interplanar separation of 3.745 (1) Å . These interactions give rise to a two-dimensional supramolecular network with layers parallel to (101) (Fig. 2).

Database survey
A search of the Cambridge Structural Database (Version 5.37, Feb 2016 with two updates; Groom et al., 2016) did not show any related metal complexes with an mpmapOH ligand. The mpmapOH ligand was newly synthesized and the title compound is the first metal complex using mpampOH ligand for this research.

Synthesis and crystallization
The title compound (I) was prepared as follows. 2-Amino-2methyl-1-propanol (4.90 g, 0.050 mol) was dissolved in MeOH (30 mL) followed by the addition of 2-pyridinecarboxaldehyde (5.41 g, 0.050 mol) under a nitrogen atmosphere. The resulting mixture was strirred at room temperature for three hours, and then NaBH 4 (6.05 g, 0.16 mol) was added slowly. The mixture was again stirred at room temperature overnight. The yellow solution was evaporated to dryness under reduced pressure. The residue was dissolved in CH 2 Cl 2 and the undissolved solids were filtered off. The solution was washed with H 2 O and dried over MgSO 4 . After removal of the drying agent and solvent, the mpmapOH ligand was obtained as a yellow oil. Yield: 6.67 g (74%

Dichlorido{2-methyl-2-[(pyridin-2-ylmethyl)amino]propan-1-ol-κ 3 N,N′,O}copper(II)
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.