{2,2′-[1,1′-(3-Azapentane-1,5-diyldinitrilo)diethylidyne]diphenolato}(piperidine)cobalt(III) tetraphenylborate

The title compound, [Co(C20H23N3O2)(C5H11N)](C24H20B) or [Co{(Me-sal)2dien}(pprdn)]BPh4, where (Me-sal)2dien is 2,2′-[1,1′-(3-azapentane-1,5-diyldinitrilo)diethylidyne]diphenolate and pprdn is piperidine, contains a pentadentate (Me-sal)2dien ligand furnishing an N3O2 set, such that two of the N and one of the O atoms of the salicylidene rings define three positions of an equatorial plane, whereas the secondary amine N atom and the other O atom of the salicylidene lie in axial positions. The piperidine ligand occupies an equatorial position trans to one of the imine N atoms of the salicylidene. In the observed conformation of the pentadentate ligand, the salicylidene rings attain asymmetrical positions owing to the structural demands. The geometry of the resulting CoN4O2 coordination can be described as distorted octahedral. The asymetric unit contains two formula units.

The title compound, [Co(C 20 H 23 N 3 O 2 )(C 5 H 11 N)](C 24 H 20 B) or [Co{(Me-sal) 2 dien}(pprdn)]BPh 4 , where (Me-sal) 2 dien is 2,2 0 -[1,1 0 -(3-azapentane-1,5-diyldinitrilo)diethylidyne]diphenolate and pprdn is piperidine, contains a pentadentate (Me-sal) 2 dien ligand furnishing an N 3 O 2 set, such that two of the N and one of the O atoms of the salicylidene rings define three positions of an equatorial plane, whereas the secondary amine N atom and the other O atom of the salicylidene lie in axial positions. The piperidine ligand occupies an equatorial position trans to one of the imine N atoms of the salicylidene. In the observed conformation of the pentadentate ligand, the salicylidene rings attain asymmetrical positions owing to the structural demands. The geometry of the resulting CoN 4 O 2 coordination can be described as distorted octahedral. The asymetric unit contains two formula units.
Cg1, Cg2 and Cg3 are the centroids of the C130-C135, C150-C155 and C230-C235 rings, respectively. Metal complexes of Schiff base ligands, aside from their wide applications, have been investigated from the coordination chemistry and structural points of view (Botteher et al., 1997;Barnes et al., 1998;Niswander & Taylor, 1997;Hirota et al., 1998;Nagata et al., 1995). Extensive investigation of the reactivity and structural aspects of metal complexes with pentadentate N 3 O 2 ligands has been carried out and it has been found that, apart from the structural demands of the pentadentate ligand, many other factors play their rôles in the realised structures of these compounds (Cini, 2001;Amirnasr et al., 2006;Morshedi et al., 2006;Meghdadi et al., 2007;Munro & Govender, 2007). In this context, we report here the synthesis and structure of [Co{(Me-sal) 2 dien}(pprdn)]BPh 4 , (I).
The asymmetric unit consists of two chemically identical, but conformationally slightly different [Co{(Me-sal) 2 dien} (pprdn)] + cations and two tetraphenylborate anions. The environment surrounding each Co III atom in (I) is distorted octahedral (Fig. 1) (Meghdadi et al., 2007, Amirnasr et al., 2001. Neither of the two six-membered chelate rings formed by (Me-sal) 2 dien is planar. The metal centres lie off the salicylaldimine fragments by 0.666 (2), 1.040 (2), 0.730 (2) and 1.099 (2) Å for O11, O21, O51 and O61, respectively, the planes themselves having a mean deviation of 0.080 Å. The conformation adopted by (Me-sal) 2 dien in (I) is different from that of (Me-sal) 2 dpt in [Co{(Me-sal) 2 dpt}(py) 2 ]PF 6 (Meghdadi et al., 2007). While the three donor N atoms of (Me-sal) 2 dpt occupy three meridional sites and the two phenolate-O atoms are trans to each other, the three N atoms of (Me-sal) 2 dien ligand in (I) are arranged in facial positions and the two phenolate-O atoms are cis. This is presumably due to the structural demands imparted by the (Me-sal) 2 dien Schiff base ligand which has forced the [Co{(Me-sal) 2 dien}(pprdn)] + to attain such a twisted structure.
Unsurprisingly, the structure owes its cohesion to a multitude of C-H···π weak interactions (Fig. 2), the shortest of them (2.94 Å) being between the C610-H61A group and the C130-C135 phenyl ring (Table 2). There are also rather marginal C-H···O hydrogen bonds, some of them intramolecular.  Stereoscopic view of the crystal structure of (I), illustrating some typical C-H···π interactions. H atoms not involved in the interactions have been omitted.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
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