Crystal structures of two dimeric nickel diphenylacetate complexes

The molecular and crystal structures of μ-aqua-κ2 O:O-di-μ-diphenylacetato-κ4 O:O′-bis[(diphenylacetato-κO)bis(pyridine-κN)nickel(II)] and μ-aqua-κ2 O:O-di-μ-diphenylacetato-κ4 O:O′-bis[(2,2′-bipyridine-κ2 N,N′)(diphenylacetato-κO)nickel(II)]–acetonitrile–diphenylacetic acid (1/2.5/1) are reported. Hirshfeld surface analysis of both compounds have been carried out.

O 2 ) 4 (C 10 H 8 N 2 ) 2 (H 2 O)]Á2.5CH 3 CNÁ-C 14 H 12 O 2 (2), the complex units are stabilized by a variety of intra-and intermolecular hydrogen bonds, as well as C-HÁ Á Á andcontacts between the aromatic systems of the pyridine, dipyridyl and diphenylacetate ligands. Despite the fact that the diphenylacetate ligand is sterically bulky, this does not interfere with the formation of the described aqua-bridged dimeric core, even with a 2,2 0 -bipyridine ligand, which has a strong chelating effect.

Chemical context
The title compounds, 1 and 2, were synthesized as a part of our ongoing research on catalytically active polynuclear Ni II and Co II carboxylate complexes with various structures and nuclearity in lactone ring-opening polymerization and ketone hydrosilylation. They belong to the type of aqua-bridged dinickel(II) carboxylates with the general formula [M II 2 (-H 2 O)(-O 2 CR) 2 (O 2 CR) 2 L n ] (n = 4 in the case of a monodentate ligand or 2 in the case of bidentate coordination), well known since the 1970s (Turpeinen, 1976). In this work, it is shown that the reaction of highly reactive synthetic hellyerite, NiCO 3 Á5.5H 2 O (Bette et al., 2016), a stoichiometric amount of diphenylacetic acid and treatment with the N-donor ligand leads to self-assembly of the title compounds. The use of sterically bulky ligands and ligands that are prone to the formation of multiple intra-and intermolecular interactions can give unexpected and interesting results (Lee et al., 2002;Nikolaevskii et al., 2016).

Structural commentary
In the title binuclear complexes, 1 and 2, each Ni II ion is sixcoordinated by two carboxylate O atoms from two bidentatebridged diphenylacetate ligands, one O atom from a monodentate diphenylacetate ligand, two N atoms from two pyridine (Py) (for 1) or one 2,2 0 -bipyridine (Bipy) ligand (for 2) and one O atom from a bridging aqua ligand in an octahedral geometry ( Figs. 1 and 2). The complexes display idealized twofold symmetry, with the axis passing through the bridging water molecule. The NiÁ Á ÁNi distances in the complexes are ISSN 2056-9890 3.5779 (4) (for 1) and 3.4826 (5) Å (for 2). Each monodentate coordinated diphenylacetate ligand is involved in the formation of an intramolecular hydrogen bond with a bridging water molecule. Hydrogen-bond geometries are specified in Tables 1 and 2.

Hirshfeld surface analysis
In order to visualize and quantitatively describe intermolecular interactions in the crystal packing of complexes 1 and 2, Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and two-dimensional fingerprint plots (McKinnon et al., 2007) were carried out and generated using CrystalExplorer (Version 17; Turner et al., 2017). The percentage contributions of the intermolecular interactions to the Hirshfeld surface are shown in Figs. 3 (for 1) and 4 (for 2).
research communications Figure 1 The molecular structure of 1, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms have been omitted for clarity.

Figure 2
The molecular structure of 2, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms and solvent molecules have been omitted for clarity.
As in the case of complex 1, close CÁ Á ÁC interplanar contacts, responsible forstacking interactions between  The two-dimensional fingerprint plots for compound 1.

Figure 4
The two-dimensional fingerprint plots for compound 2.

Figure 5
The Hirshfeld surface mapped over d norm for compound 1 in the range À0.4078 to 1.4837 a.u.
Bipy ligands, are displayed as patches of combined blue and red triangles on the surface over shape index (Fig. 8). Hirshfeld surface of compound 1 plotted over shape-index.

Figure 7
The Hirshfeld surface mapped over d norm for compound 2 in the range À0.7804 to 1.5753 a.u. 6. Synthesis and crystallization 6.1. Compound 1 A suspension of synthetic hellyerite, NiCO 3 Á5.5H 2 O (0.653 g, 3.0 mmol), in acetonitrile (40 ml) was added to a solution of diphenylacetic acid (1.274 g, 6.0 mmol) in 10 ml acetonitrile. After full conversion of hellyerite, pyridine (0.485 ml, 6.0 mmol) was added and the solution was refluxed for 15 min. The resulting pale-green-blue solution was cooled to room temperature and filtered. After a few days, blue crystals of 1 were collected by filtration (yield $70%).

Compound 2
The synthesis of compound 2 was carried out in a similar manner to the synthesis of compound 1, but 2,2 0 -bipyridine (0.469 g, 3.0 mmol) was added instead of pyridine. The resulting blue solution was cooled to room temperature and filtered. After a few days, blue crystals of 2 were collected by filtration (yield $60%).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The H atoms of the water molecules were located in difference Fourier maps and refined freely. The other H atoms were placed in calculated positions and refined using a riding model, with C-H = 0.98 Å and U iso (H) = 1.2U eq (C) for the tertiary C atoms, C-H = 0.93 Å and U iso (H) = 1.2U eq (C) for aromatic C atoms, and C-H = 0.96 Å and U iso (H) = 1.5U eq (C) for methyl groups.

Computing details
For both structures, data collection: CrysAlis PRO (Rigaku OD, 2017); cell refinement: CrysAlis PRO (Rigaku OD, 2017); data reduction: CrysAlis PRO (Rigaku OD, 2017); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009) and DIAMOND (Brandenburg, 2012); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009). 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.

acetonitrile-diphenylacetic acid (1/2.5/1) (2)
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.48 e Å −3 Δρ min = −0.57 e Å −3 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.