Crystal structure of aquachlorido(nitrato-κ2 O,O′)[1-(pyridin-2-yl-κN)-2-(pyridin-2-ylmethylidene-κN)hydrazine-κN 2]manganase(II)

The asymmetric unit comprises a discrete molecule in which the cation MnII is heptacoordinated. The environment around the cation is an almost perfect pentagonal bipyramid. In the crystal, extensive hydrogen bonding leads to a three-dimensional framework.

The search for novel manganese(II) compounds having interesting magnetic properties, using 1-(pyridin-2-ylmethylidene)-2-(pyridin-2-yl)hydrazine (HL) as a tridendate ligand, led to the preparation of the title mononuclear material, [MnCl(NO 3 )(C 11 H 10 N 4 )(H 2 O)], and the determination of its structure by XRD. The asymmetric unit comprises a discrete molecule in which the cation Mn II is heptacoordinated. The environment around the cation is an almost perfect pentagonal bipyramid. The base is defined by the two N atoms of the pyridine rings, the N atom of the imino function of the ligand and the two O atoms of the chelating bidentate nitrate ligand. The apical positions are occupied by a Cl atom and a water molecule. In the crystal, there are numerous hydrogen bonds of the types Ow-HÁ Á ÁONO 2 and C-HÁ Á ÁONO 2 , which generate layers parallel to the bc plane in which the ligands in the axial positions point into the interlayer space. These axial ligands give rise to hydrogen bonds of the types Ow-HÁ Á ÁONO 2 , Ow-HÁ Á ÁCl, N-HÁ Á ÁCl and C-HÁ Á ÁCl, leading to a threedimensional framework. The chain bridging the two pyridine rings is disordered over two sets of sites in a 0.53 (2):0.47 (2) ratio.

Chemical context
Although very much studied, the coordination chemistry of manganese remains very interesting as this metal can have several degrees of oxidation and its complexes can display different coordination numbers and geometries that are not always easily predicted (Chiswell et al., 1987;Baldeau et al., 2004;Mikuriya et al., 1997). Although the coordination numbers four and six are the most common in the coordination chemistry of manganese, the coordination numbers five, seven and eight are also observed (Louloudi et al., 1999). As a result of the multiple degrees of oxidation of this metal, interest in the coordination chemistry of manganese complexes is considerable. The involvement of manganese in various important biological processes such as oxidation of water by photosynthetic enzymes (Whittaker & Whittaker, 1997), hydrogen peroxide disproportionation by catalase (Meier et al., 1996), superoxide dismutase (SOD) (Schwartz et al., 2000), ribonucleotide reductase and lipoxygenase (Baffert et al., 2003) increases the interest of scientists in this metal. These examples from nature inspire chemists to search for biomimetic catalysts of these metalloenzymes that are highly selective and cause little damage to the environment ISSN 2056-9890 (Krishnan & Vancheesan, 1999). Manganese complexes are also used as catalysts in many processes such as epoxidation of alkene (Castaman et al., 2009), oxidation (Wegermann et al., 2014) and hydrogenation of ketones (Bruneau-Voisine et al., 2017). The involvement of the metal center in these processes depends as much on its degree of oxidation as on its coordination number in the complex. The synthetic procedures adopted are essential for yielding complexes with specific properties. In this context, for the synthesis of the heptacoordinated Mn II title complex, we use a one-pot synthesis method, which is an efficient approach to prepare a large variety of coordination compounds (Oyaizu et al., 2000). Manganese dichloride tetrahydrate is mixed with the synthesized organic ligand (HL), which provides three soft nitrogenbinding sites in the presence of nitrate anions that can act with hard oxygen-binding sites to yield a mononuclear heptacoordinated manganese(II) complex.

Structural commentary
The structure of the title complex is shown in Fig. 1. The asymmetric unit comprises a discrete molecule in which the cation Mn II is heptacoordinated. The coordination polyhedron of the Mn II center is best described as a distorted pentagonal bipyramid with an MnN 3 O 3 Cl chromophore. The basal plane is occupied by two nitrogen atoms from the pyridine rings, one nitrogen atom from the imino function and two oxygen atoms from the chelating bidentate nitrate group. The metal-bound ligand nitrogen atoms exhibit angles of 69.85 (7) (N1-Mn1-N2) and 69.62 (7) (N2-Mn1-N4) which are slightly different from the ideal angle for a regular pentagon (72  (14) Å ]. The two pyridine rings are connected by a disordered chain C-CH=N-NH-C in which the bond lengths are slightly different from those observed in similar complexes; this may be related to the observed disorder. Two intramolecular hydrogen bonds, C1-H1Á Á ÁO2 and C11-H11Á Á ÁO3, are also observed in the structure (

Figure 1
An ORTEP view of the title compound, showing the atom-numbering scheme and intramolecular hydrogen bonds as dashed lines. Displacement ellipsoids are plotted at the 50% probability level.

Supramolecular features
In the crystal, the complex molecules are linked by hydrogen bonds, giving rise to a three-dimensional network (Fig. 2, Table 2). The structure is built up from pentagonal bipyramids around the Mn II atom, which are assembled in layers parallel to the bc plane. These layers are interconnected by hydrogen bonds. The coordinating axial water molecule points into the interlayer space and act as a hydrogen-bond donor towards oxygen atom O2-NO 2 and chlorine atom Cl1 (Fig. 2) via the hydrogen bonds O1W-H1WBÁ Á ÁO2 ii and O1W-H1WAÁ Á ÁCl1 i , [symmetry codes: (i) x + 1, y, z; (ii) Àx + 2, Ày + 1, Àz + 2]. The axial Cl1 atom points also in the interlayer space and acts as a hydrogen-bond acceptor toward N3-H3NÁ Á ÁCl1 iii and C6-H6Á Á ÁCl1 iii [symmetry code: (iii) Àx + 1, Ày + 1, Àz + 1]. The combined hydrogen bonds link the layers into a three-dimensional framework. Within a layer, the molecules are interconnected by hydrogen bonds of the type C-HÁ Á ÁONO 2 [C8-H8Á Á ÁO4 iv -NO 2 ; symmetry code: (iv) x, y, z À 1].  , Cu II (Mesa et al., , 1989Rojo et al., 1988;Ainscough et al., 1996;Chowdhury et al., 2009;Mukherjee et al., 2010;Chang et al., 2011), Co II (Gerloch et al., 1966), Ni II (Chiumia et al., 1999) and Zn II (Dumitru et al., 2005;. In all cases, the ligand behaves as a tridentate ligand acting through the soft nitrogen donor atoms from the two pyridine rings and the imino function. The hard protonated nitrogen atom remains uncoordinated in all complexes.

Synthesis and crystallization
A mixture of 2-hydrazinopyridine (1 mmol) and 2-pyridinecarbaldehyde (1 mmol) in ethanol (10 mL) was stirred under reflux for 30 min. A mixture of ammonium nitrate (3 mmol) and MnCl 2 Á4H 2 O (1 mmol) in ethanol (10 mL) was added to the solution. The mixture was stirred for 30 min and the resulting yellow solution was filtered and the filtrate was kept at 298 K. A yellow powder appeared after one day and was collected by filtration, yield 65%. Analysis calculated for [C 11 H 12

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All H atoms ( CH, NH and OH 2 groups) were optimized geometrically (C-H = 0.93, N-H = 0.86 and O-H = 0.87-0.91 Å ) and refined as riding with U iso (H) = 1.2U eq (C) or 1.5U eq (O). The chain bridging the two pyridine rings is disordered. This disorder may be explained by the fact that the sequence of atoms C(Py)-CH N-NH-C(py) overlaps with the sequence C(py)-NH-N CH-C(py), meaning two orientations of the ligand. In  such a case, for the refinement it was assumed that the C atom of the CH group from one chain and the NH atoms from the second chain occupy the same position. The same relates inversely. The occupancy factor refined to 0.53 (2):0.47 (2).

Aquachlorido(nitrato-κ 2 O,O′)[1-(pyridin-2-yl-κN)-2-(pyridin-2-ylmethylidene-κN)hydrazine-κN 2 ]manganase(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.