(Dicyanamido)[tris(2-pyridylmethyl)amine]zinc(II) perchlorate

In the title complex, [Zn(C2N3)(C18H18N4)]ClO4, the ZnII ion has a slightly distorted trigonal–bipyramidal ZnN5 coordination geometry. The crystal structure is stabilized by weak intermolecular C—H⋯O and C—H⋯N hydrogen bonds. In addition, there are relatively close contacts between the O atoms of the perchlorate anion and symmetry-related pyridine rings [O⋯Cg = 3.179 (3) and 3.236 (3) Å, where Cg is the centroid of a pyridine ring], and between the terminal N atom of the dicyanamide ligand and pyridine rings [N⋯Cg = 3.381 (4)–3.761 (3) Å]. The central N atom of the dicyanamide ligand is disordered over two sites in an approximately 0.6:0.4 ratio.

In the title complex, [Zn(C 2 N 3 )(C 18 H 18 N 4 )]ClO 4 , the Zn II ion has a slightly distorted trigonal-bipyramidal ZnN 5 coordination geometry. The crystal structure is stabilized by weak intermolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds. In addition, there are relatively close contacts between the O atoms of the perchlorate anion and symmetry-related pyridine rings [OÁ Á ÁCg

Comment
Tris[(2-pyridyl)methylene)amine is a very common terminal ligand and many complexes containing this ligand have been reported, including some Zn(II) complexes with perchlorate anions (e.g. Makowska-Grzyska et al., 2003) such as in the title compound. The dicyanamide anion can play a role as bridging ligand to form multi-nuclear complexes (e.g. Sun et al., 2003;Martin et al., 2001). As part of our work we wanted to prepare a coordination polymer with dicyanamide group acting as a bridging ligand and tris[(2-pyridyl)methylene)amine as terminal ligand, but instead we obtained the title mononuclear five-coordinated Zn(II) complex (I) and its crystal structure is reported herein. At this time there appears to be no other published examples of crystal structures of complexes of the two above mentioned ligands both coordinated to a transition metal.
The title complex is shown in Fig. 1. The Zn II ion is in a slightly distorted trigonal-bipyramidal coordination geometry.

Experimental
A 10 ml me thanol solution of tris[(2-pyridyl)methylene]amine (0.2103 g, 0.72 mmol) was added into 20 ml H 2 O solution containing Zn(ClO 4 )6H 2 O (0.2621 g, 0.70 mmol) and sodium dicyanamide (0.0645 g, 0.72 mmol), and the mixture was stirred for a few minutes. Colorless single crystals were obtained after the filtrate had been allowed to stand at room temperature for 10 d.

Refinement
The central N atom of the dicyanamide ligand is disorded over two sites in a 0.40 (7): 60 (7) ratio (sum constrained to unity).
H atoms were placed in calculated positions (C-H = 0.97 Å for methylene group and C-H = 0.93 Å for other H atoms) and refined as riding with U iso = 1.2 U eq (C).  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.