Di-μ1,1-azido-bis[(2-{1-[2-(isopropylamino)ethylimino]ethyl}phenolato)copper(II)]

In the centrosymmetric binuclear title complex, [Cu2(C13H19N2O)2(N3)2], the CuII atom adopts an elongated CuON4 square-based pyramidal coordination geometry, arising from the N,N′,O-tridentate ligand and two bridging end-on azide anions. The O atom is in the basal plane, one of the azide N atoms is in the apical site and the Cu⋯Cu separation is 3.2365 (3) Å. A pair of intramolecular N—H⋯O hydrogen bonds helps to establish the molecular conformation.

In the centrosymmetric binuclear title complex, [Cu 2 (C 13 H 19 N 2 O) 2 (N 3 ) 2 ], the Cu II atom adopts an elongated CuON 4 square-based pyramidal coordination geometry, arising from the N,N 0 ,O-tridentate ligand and two bridging end-on azide anions. The O atom is in the basal plane, one of the azide N atoms is in the apical site and the CuÁ Á ÁCu separation is 3.2365 (3) Å . A pair of intramolecular N-HÁ Á ÁO hydrogen bonds helps to establish the molecular conformation.

Comment
Polynuclear complexes containing bridging groups are of great interest because of their versatile molecular structures and applications (Massoud et al., 2007;Lisnard et al., 2007;Sarkar et al., 2004). In the last few years chemists have dedicated their efforts to the study of molecular-based magnetic materials. One strategy for the design of molecular based magnets involves assembling of paramagnetic metal ions in one-, two-and three-dimensional networks using suitable bridging ligands (Escuer & Aromí, 2006;Goher et al., 2001;Colacio et al., 2005;Sailaja et al., 2003). The azide ligands have been widely used because of their diverse binding modes that yield different types of molecules such as dimmers, tetramers, one-, two-, or three-dimensional arrays (Cheng et al., 2006;Meyer et al., 2005;Sharma, 1990;Ko et al., 2006;Escuer et al., 1998). In the present work, the title new end-on azido-bridged dinuclear copper(II) complex, (I), containing the deprotonated form of 2-[1-(2-isopropylaminoethylimino)ethyl]phenol), HL, has been prepared and structural characterized.
The structure of the complex is shown in Fig. 1. There are two unique units [CuL] linked by double end-on azido bridging groups with an inversion center at the midpoint of the two Cu atoms. Each Cu atom in the complex is in a square pyramidal environment consisting of the NNO donor set from one Schiff base ligand and two N atoms from two bridging azido groups.
The Cu···Cu distance is 3.236 (1) Å. The Cu-O and Cu-N bond lengths are comparable to the corresponding values observed in other similar copper(II) complexes with azido bridges (Triki et al., 2005;Gao et al., 2005;Zhang et al., 2001).
There are two N-H···O hydrogen bonds (Table 1) between the two symmetry-related two CuL units (Fig. 2).

Experimental
A mixture of NaN 3 (0.065 g, 1 mmol) and Cu(NO 3 ) 2 .3H 2 O (0.241 g, 1 mmol) in 50 ml methanol was stirred for half an hour with heating, then HL (0.220 g, 1 mmol) was added to the solution and the reaction continued to stirred for 1 h. After filtration, the blue filtrate was allowed to stand at room temperature for a week to deposit blue blocks of (I) in 54% yield.

Refinement
H atoms were placed in geometrically idealized positions and allowed to ride on their parent atoms, with C-H = 0.93-0.98 Å, N-H = 0.91 Å, and with U iso (H) = 1.2U eq (C,N) and 1.5U eq (C methyl ). Fig. 1. The molecular structure of (I) showing 30% probability displacement ellipsoids. The dashed lines indicate the N-H···O hydrogen bonds. Unlabelled atoms are generated by (1-x, -y, 1-z).

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 > σ(F 2 ) is used only for calculating Rfactors(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.