Crystal structure of trans-bis[2-(1H-benzotriazol-1-yl)acetato-κO]bis(ethanolamine-κ2 N,O)copper(II)

The copper(II) atom shows a typical Jahn–Teller distorted [4 + 2] octahedral coordination sphere.

The reaction of 2-(1H-benzotriazol-1-yl)acetic acid (HBTA; C 8 H 7 N 3 O 2 ) and monoethanolamine (MEA; C 2 H 7 NO) with CuCl 2 Á2H 2 O resulted in the formation of the title complex, [Cu(C 8 H 6 N 3 O 2 ) 2 (C 2 H 7 NO) 2 ] or [Cu(BTA) 2 (MEA) 2 ]. Its asymmetric unit comprises one BTA anion coordinating to the Cu 2+ cation (site symmetry 1) through the carboxyl O atom, and one MEA ligand chelating the metal cation by two heteroatoms (O and N). The equatorial Cu-O and Cu-N bond lengths are similar at 2.029 (1) and 1.980 (2) Å , respectively, while the length of the axial Cu-O bond is considerably greater [2.492 (2) Å ], as is typical for Jahn-Teller-distorted systems. An intramolecular hydrogen bond is present between the hydroxy group of the MEA ligand and the non-coordinating O atom of the carboxylate group. Intermolecular hydrogen bonding involving the amino function of the MEA ligand and the carboxylate group results in eight-membered rings with an R 2 2 (8) graph-set motif. The molecules are further linked by C-HÁ Á Á interactions involving the triazole rings and methylene groups of MEA, thus generating an overall three-dimensional supramolecular framework.

Structural commentary
The molecular structure of trans-bis(ethanolamine-2 N,O)bis-[2-(1H-benzotriazol-1-yl)acetato-O]copper(II), (I), is shown in Fig. 1 and consists of isolated [Cu(MEA) 2 (BTA) 2 ] units. The Cu 2+ cation is located on a center of inversion. Its coordination polyhedron is a distorted N 2 O 4 octahedron formed by two oxygen atoms (O2) of the carboxy groups of symmetryrelated BTA anions, by two nitrogen atoms (N4) of two symmetry-related MEA ligands in the equatorial plane and by two O atoms (O3) of the same set of MEA ligands in the axial positions. The Cu-O2 and Cu-N4 bond lengths are 2.029 (1) and 1.980 (2) Å , respectively, whereas the length of the axial Cu-O3 bond is 2.492 (2) Å , typical for Jahn-Teller distortions. The MEA ligand is neutral and acts as a bidentate Nand O-donor ligand and forms CuNC 2 O five-membered chelate rings which have a twist conformation; the O3-C10-C9-N4 torsion angle is À60.3 (3) . The planar benzotriazole ring system (N1-N3/C1-C6: r.m.s. deviation = 0.0064 Å ) is coplanar with the methyl carbon atom C7 [deviation from the plane of 0.158 (2) Å ], whereas the carboxylate group is nearly normal to this plane [88.0 (2) ]. The difference of the C8-O(1,2) distances of the carboxylate group (Á = 0.036 Å ) is due to the monodentate coordination, with the longer C-O distance involving the coordinating O2 atom.
The molecular structure is stabilized by an intramolecular O3-H3Á Á ÁO1 hydrogen bond between the OH group of the MEA ligand and the non-coordinating carboxylate O atom ( Fig. 1, Table 1).

Figure 1
The molecular structure of [Cu(MEA) 2 (BTA) 2 ] with the atomnumbering scheme. Displacement ellipsoids are drawn at the 25% probability level.

Figure 2
Chain structures formed by hydrogen bonds in the structure of (I).
Hydrogen bonds are shown as dashed lines.

Database survey
There are thirty-one structures of coordination compounds that are derived from 2-(1H-benzotriazol-1-yl)acetic acid and different metal cations in the CSD (Version 5.39, last update August 2018; Groom et al., 2016). The interaction of metal ions with BTA results in the formation of complexes in which metals demonstrate monodentate [CUYGAG (Ma et al., 2015),

Synthesis and crystallization
To an aqueous solution (2.5 ml) of CuCl 2 Á2H 2 O (0.048 g, 0.282 mmol) was slowly added an ethanol solution (5 ml

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound hydrogen atoms were placed in calculated positions and refined as riding atoms with C-H = 0.93 and 0.97 Å for aromatic and methylene hydrogen atoms, respectively, and with U iso (H) = 1.2U eq (C). The positions of the O-and N bound H atoms were located from a difference-Fourier map and were refined with soft distance restraints, 0.82 Å for the hydroxyl group and 0.95 Å for the primary amine group.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq