Bis[benzyl 2-(heptan-4-ylidene)hydrazine-1-carboxylate]bis(thiocyanato)cobalt(II)

The title compound, [Co(NCS) 2 (C 15 H 22 N 2 O 2 ) 2 ] or C 32 H 44 CoN 6 O 4 S 2 , was prepared from cobalt(II) nitrate, benzyl carbazate and ammonium thiocyanate in the presence of 4-heptanone. The compound crystallizes with two centrosymmetric complexes in which the cobalt(II) atoms have a trans -CoO 2 N 4 octahedral coordination geometry. In the crystal, N—H (cid:2) (cid:2) (cid:2) S, C—H (cid:2) (cid:2) (cid:2) S and C— H (cid:2) (cid:2) (cid:2) . (cid:2) contacts stack the complex molecules along the b -axis direction.


Structure description
Our previous work involving Schiff-base complexes derived from benzyl carbazate and carbonyl compounds was limited to short-chain dialkyl ketones (Nithya et al., 2016(Nithya et al., , 2017. In order to investigate and compare the coordinating ability of benzyl carbazate Schiff bases derived from higher homologues, we have prepared the title cobalt complex from benzyl carbazate with 4-heptanone with thiocyanate as the charge-balancing anionic ligand. We report the molecular and crystal structure of the complex here. Neither the structure of the bidentate ligand used here, nor of its complexes, have been reported previously. The title compound, Co(C 15 H 22 N 2 O 2 ) 2 (NCS) 2 , crystallizes with two centrosymmetric, octahedral cobalt(II) complexes (1) and (2) in the monoclinic unit cell. These are differentiated in the numbering scheme by leading 1 and 2 characters, respectively (Fig. 1). The molecules overlay with an r.m.s. deviation of 0.602 Å (Fig. 2), with the greatest conformational differences in the vicinity of the n-propyl substituents on C12 and C22 (Macrae et al., 2008). The benzyl-2-(heptan-4-ylidene)hydrazine-1-carboxylate ligand is N,O-bidentate with two such ligands in the equatorial plane, binding through the imine N and carbonyl O atoms. The N bound thiocyanato ligands occupy trans-axial positions and are slightly kinked, with N-C-S and Co-N-C bond angles of 177.3 (6) and 169.8 (5) , respectively, in (1) and 178.9 (6) and 165.6 (6) , respectively, in (2). With the exception of the di-n-propyl substituents on the C12 and C22 carbon atoms, the nonhydrogen atoms of the bidentate ligands lie close to the equatorial planes of both complexes with r.m.s. deviations from the best-fit plane through N11, N12, O11, C11, O12, C13Á Á ÁC19 of 0.079 Å for (1) and 0.094 Å for the corresponding plane in (2). Pairs of intramolecular C-HÁ Á ÁO hydrogen bonds form in both molecules, Table 1, Fig. 1. In the crystal, N-HÁ Á ÁS and weaker C-HÁ Á ÁS hydrogen bonds combine with a C-HÁ Á Á contact between molecules (1) and (2), Table 1, to stack the complexes along the b-axis direction, Fig. 3.

Synthesis and crystallization
Cobalt(II) nitrate (0.146 g, 0.50 mmol) dissolved in 10 ml of doubly distilled water was added to a methanolic solution (10 ml) of benzyl carbazate (0.166 g, 1.00 mmol) and ammonium thiocyanate (0.076 g, 1.00 mmol). The solution was then layered with 4-heptanone (0.1 ml, 1 mmol) and the colour changed from pink to blue. The resulting mixture was retained for slow evaporation at room temperature, resulting in olivegreen crystals, which were collected, washed with water and air-dried. Yield 81.5% (0.119 g) with respect to the metal.

Figure 3
A view of the overall packing of the title compound along the b-axis direction. Hydrogen bonds are drawn as cyan dashed lines and a representative C-HÁ Á Á(ring) contact is shown as a green dashed line, with a red sphere representing the ring centroid.

Figure 2
An overlay of the two unique molecules of the title compound (r.m.s. deviation = 0.602 Å ).

Data collection
Agilent SuperNova, Dual, Cu at zero, Atlas diffractometer Radiation source: sealed X-ray tube, SuperNova (Cu) X-ray Source Detector resolution: 5.1725 pixels mm -1 ω scans Absorption correction: gaussian (CrysAlis PRO; Agilent, 2014) T min = 0.839, T max = 0.912 34985 measured reflections 7198 independent reflections 4299 reflections with I > 2σ(I) Hydrogen site location: mixed H atoms treated by a mixture of independent and constrained refinement 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. Refinement. l reflection with Fo >>> Fc was omitted from the final refinement cycles.