Crystal structure of dichlorido-1κCl,2κCl-(μ2-3,5-dimethyl-1H-pyrazolato-1κN 2:2κN 1)(3,5-dimethyl-1H-pyrazole-2κN 2){μ-2-[(2-hydroxyethyl)amino-1κ2 N,O]ethanolato-1:2κ2 O:O}dicopper(II)

The title pyrazolate aminoalcohol complex comprises two dimethylpyrazole molecules in monodentate and bidentate-bridged coordination modes and a monodeprotonated diethanolamine molecule.


Chemical context
Metal complexes of paramagnetic metal ions formed by polynucleative or polydentate ligands are of great interest as they often exhibit non-trivial magnetic behaviour (Gumienna-Kontecka et al., 2007;Suleimanov et al., 2015;Gural'skiy et al., 2012). Among polydentate and polynucleative ligands, those containing both nitrogen and oxygen donor atoms are probably the most versatile and efficient chelators for the vast majority of metal ions (Pavlishchuk et al., 2010(Pavlishchuk et al., , 2011Strotmeyer et al., 2003). Amino alcohol ligands and their derivatives are one of the most widely used representatives of N,Ochelators and attract attention as strong polydentate ligands that can form coordination compounds with transition metals (Hughes et al., 1972). Amino alcohols contain both amino and hydroxyl groups within the same molecule, and therefore they are good chelating and bridging ligands. Polynuclear complexes of 3d metals with amino alcohols or their deprotonated forms can show non-trivial properties as catalysts, materials with different magnetic properties or biologically active compounds (Reiter et al., 2006). Amino alcohol ligands are used to prepare copper(II) amino alcoholates that can selfassemble to form both mono-and multinuclear complexes. In bionuclear copper complexes, the metal atoms can be connected by bridged oxygen atoms (alkoxy) from two different diethanolamine molecules (Tudor et al., 2003;Marin et al., 2005), or combined by a single oxygen atom from an amino alcohol and a bridged ligand molecule (Ashurov et al., 2015). There are several typical binding modes of tridentate amino alcohol ligands to copper(II) ions and other metals such as lanthanides, yttrium, and alkaline-earth metals (Breeze & Wang, 1994;Chen et al., 1995;Wang et al., 1995). It is a wellknown fact that copper coordination compounds can be modified with amino alcohols. For example, copper complexes with theophylline show promising potential antitumor action and can be modified with diethanolamine by similar coordination of amino alcohols to the copper atom (Madará sz et al., 2000). Studies of both tridentate-and bidentate-coordinated amino alcohol ligands to the copper atom have been carried out (Wang, 1995). Complexes of 3d metals with a tricoordinated diethanolamine are interesting objects for synthesis and further studies (Buvaylo et al., 2009). Considering the above, we understand the importance of accumulating a theoretical information base on such coordination compounds, and therefore in this article we report the synthesis and crystal structure of a new binuclear mixed-ligand copper(II) complex containing 3,5-dimethylpyrazole and diethanolamine (Fig. 1).

Structural commentary
The crystal structure of the title compound ( Fig. 2) consists of dinuclear Cu 2 (Hdmpz)(dmpz-H)(HDEA)Cl 2 (Hdmpz = 3,5dimethyl-1H-pyrazole, dmpz-H = deprotonated 3,5-dimethylpyrazole, and HDEA = monodeprotonated diethanolamine) units enclosed in two antisymmetrically oriented rows along the a axis. The unit cell consists of two unrelated structural fragments from both rows (Fig. 2). Along the a axis within one row, each molecule is bonded to the preceding and subsequent ones by hydrogen bonds of the same length. Along the b axis, the formation of molecules into dimers is due to hydrogen bonds of equal length between the bridged oxygen atom and the non-deprotonated hydroxy group of the adjacent molecule. The title dinuclear pyrazolate amino-alcohol compound forms a cyclic structure. Two copper atoms bridged by an oxygen atom of a deprotonated diethanolamine and by a molecule of deprotonated dimethylpyrazole form a fivemembered bimetallic ring. The five-membered metallocycle has a non-planar structure. The N atoms of the bridging molecule of dimethylpyrazole are in the plane of the metallocycle while the bridging O atom is out of this plane by 0.802 (1) Å . The angle between the Cu1/O1/Cu2 and Cu1/Cu2/ N3/N4 planes is 45.85 (8) . The geometrical environment of Cu1 with a coordination number of 4 is different from that of Cu2, which exhibits a coordination number of 5. The Cu1 atom is in a distorted tetrahedral environment formed by the pyridine N atom of the non-deprotonated dimethylpyrazole molecule, the N atom of the deprotonated bridging dimethylpyrazole, the Cl atom and the bridging O atom of the monodeprotonated diethanolamine. The environment of the Cu2 metal center is intermediate between trigonal bipyramidal and square pyramidal, formed by the N atom of the deprotonated bridged dimethylpyrazole, the Cl atom and the aminoalcohol N atom, and two O atoms of the deprotonated and non-deprotonated OH groups. The intermetallic distance The crystal packing of the title compound viewed along the a-axis direction.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.
between Cu1 and Cu2 is 3.2439 (4) Å . The diethanolamine fragment is coordinated by all donor atoms to copper in a tridentate mode (with atom O1 bridging the two metal centers Cu1 and Cu2) and forms two similar non-planar fivemembered metallocycles. It is worth mentioning that the Cu1-O1 distance of 1.9388 (13) Å (Table 1) differs significantly from the Cu2-O2 distance of 2.2441 (14) Å .

Supramolecular features
In the crystal, hydrogen bonds (Table 2) are observed between the N and Cl atoms (N1-H1Á Á ÁCl2 and N5-H5Á Á ÁCl1) leading to the formation of antisymmetric chains running along the a-axis direction (Fig. 3). Adjacent chains are connected by hydrogen bonds between the hydroxyl group as donor and the O1 atom of the adjacent molecule as acceptor. There are different fragments that are potential H-atom donors or acceptors and further analysis of the structure indicates the presence of multiple non-covalent intermolecular interactions.

Figure 3
The hydrogen bonds (dotted lines) in the crystal structure of the title compound.

Figure 4
Partial view of the one-dimensional architecture in the crystal structure of the title compound. Non-relevant H atoms are omitted for clarity.

Figure 5
Two projections of Hirshfeld surfaces mapped over d norm showing the intermolecular interactions within the molecule. Red areas represent contacts shorter than the sum of the van der Waals radii, while blue areas represent regions where contacts are longer than the sum of van der Waals radii, and white areas are zones close to the sum of van der Waals radii.
copper atom) gave 168 hits. Most similar to the title compound are the dinuclear complexes with coordinated diethanolamine molecules, and copper atoms connected by a bridging oxygen atom and some other ligands, see: refcodes ELESAP (Tudor et al., 2003), FARKAL (Marin et al., 2005) and WITBAC (Madará sz et al., 2000).

Synthesis and crystallization
A 1.76 mmol diethanolamine solution was added dropwise to a 1.15 mmol acetonitrile solution of complex Cu 4 ( 2 -Cl) 6 ( 4 -O)(C 5 H 8 N 2 ) 4 under stirring. The mixture was stirred for a further 2 h with oxygen access and without heating. Amino alcohol was added to the brown solution and the colour of the mixture changed to green. Dark-green crystals of the title compound suitable for a single crystal X-ray analysis were obtained in 55% yield by slow gas diffusion in an acetonitrile/ hexane isolated system. Elemental analysis of C 14 H 25 Cl 2 Cu 2 N 5 O 2 : found C 33. 96, H 5.267 and N 14.13% (calculated C 34.08, H 5.1, N 14.19%). The starting compound Cu 4 ( 2 -Cl) 6 ( 4 -O)(C 5 H 8 N 2 ) 4 is a polymorphic modification of the already known tetranuclear copper pyrazole-containing cluster Cu 4 OCl 6 (C 5 H 8 N 2 ) 4 and was obtained from the Cu-CuCl 2 Á2H 2 O-Hdmpz system.