Bis(tri-2-pyridylamine)nickel(II) bis(perchlorate)

In the title compound, [Ni(C15H12N4)2](ClO4)2, the NiII atom lies on an inversion center and is octahedrally coordinated by the N atoms of two tridentate tri-2-pyridylamine ligands. The two perchlorate anions are disordered over two sites with a refined occupancy ratio of 0.528 (19):0.472 (19).

In the title compound, [Ni(C 15 H 12 N 4 ) 2 ](ClO 4 ) 2 , the Ni II atom lies on an inversion center and is octahedrally coordinated by the N atoms of two tridentate tri-2-pyridylamine ligands. The two perchlorate anions are disordered over two sites with a refined occupancy ratio of 0.528 (19):0.472 (19).

Experimental
Crystal data [Ni(C 15  Bis(tri-2-pyridylamine)nickel(II) bis(perchlorate) S. Wang, W. He and W. Huang Comment Luminescent organic and coordination compounds have been an active research area for decades because of their various potential applications in materials sciences. It has been demonstrated that 2,2'-dipyridylamine can produce a bright blue luminescence when deprotonated and bound to either an aluminium ion or a boron center (Liu et al., 1997). However, many of the previously reported aluminium or boron compounds based on 2,2'-dipyridylamine are not stable enough for electroluminescent devices. The neutral tripodal ligand 2,2',2''-tripyridylamine and its derivatives with Zn(II), Cd(II) and Hg(II) have been investigated for their optical properties (Yang et al., 1999). However, its complexes with d 8 metal(II) remain unkown. By using the 2,2',2''-tripyridylamine ligand, we report here the synthesis and crystal structure of the title compound, bis(2,2',2''-tripyridylamine)nickel(II) bis(perchlorate), (I).
The structure of (I) consists of monomeric [Ni(2,2',2''-tpa) 2 ] 2+ cations and associated ClO 4 anions. The Ni atom lies on an inversion center. As shown in Fig. 1, the Ni center is six-coordinate with an octahedral geometry. In principle, 2,2',2''-tpa can function not only as a tridentate chelating ligand but also as a bidentate chelating ligand where only two pyridyl groups bind to the same central atom (Wang et al., 2009). In the title compound, each 2,2',2''-tpa ligand functions as a tridentate ligand, chelating to the nickel center. The two perchlorate anions are disordered over two sites with a refined occupancy ratio of 0.528 (19) : 0.472 (19).
A solution of 2,2',2''-tpa (62.11 mg, 0.2 mmol) in acetonitrile (5 ml) was added dropwise to a solution of Ni(ClO 4 ) 2 .6H 2 O (36.58 mg, 0.1 mmol) in acetonitrile (2 ml). The mixture was stirred at room temperature for 5 min and then filtered. Light purple crystals of (I) suitable for X-ray analysis were obtained by slow diffusion of filtrate.

Refinement
The two perchlorate anions are disordered over two sites with a refined occupancy ratio of 0.528 (19) Fig. 1. The structure of (I), shown with 30% probability displacement ellipsoids. The disordered perchlorate anions and H atoms have been omitted for clarity. Unlabeled atoms are related to labeled atoms by inversion symmetry.

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. 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 > 2sigma(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.