[N-(1-Azanidyl-2,2,2-trichloroethylidene)-2,2,2-trichloroethanimidamide]copper(II)

The title compound, [Cu(C4H2Cl6N3)2], was obtained by the reaction of CCl3CN with ammonia in presence of CuCl. The CuII atom is located about an inversion centre. The molecule consists of three planar units (one central square CuN4 and two C2N3 fragments), adopting a staircase-like structure. The six-membered metallocycles have a sofa conformation with the Cu atom out of the plane of the 1,3,5-triazapentadienyl ligands by 0.246 (5) Å. The ipso-C atoms of the CCl3 substituents are slightly out of the 1,3,5-triazapentadienyl planes by 0.149 (6) and −0.106 (6) Å. The CCl3 groups of each 1,3,5-triazapentadienyl ligand are practically in the energetically favourable mutually eclipsed conformation. In the crystal, the molecules are packed in stacks along the a axis. The molecules in the stacks are held together by two additional axial Cu⋯Cl interactions of 3.354 (2) Å. Taking the axial Cu⋯Cl interactions into account, the CuII atom exhibits a distorted [4 + 2]-octahedral coordination environment. The stacks are bound to each other by weak intermolecular attractive Cl⋯Cl [3.505 (2)–3.592 (3) Å] interactions.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: AA2069). Recently we have discovered a new catalytic olefination reaction as a general method for the preparation of alkenes from polyhalogenated compounds and hydrazones ( Fig. 1) Korotchenko et al., 2001;Nenajdenko et al., 2003Nenajdenko et al., , 2004aNenajdenko et al., , 2004bNenajdenko et al., , 2005Nenajdenko et al., , 2007.
During our study of the catalytic olefination reaction we have found that the reaction with trichloroacetonitrile demand the use of ethylenediamine as a base because in the case of ammonia no target alkene is formed (Nenajdenko et al., 2004c). We decided to study the reaction of CCl 3 CN with ammonia in presence of CuCl more thoroughly and found that the formation of the title copper (II) chelate complex takes place (Fig. 2). The formation of this complex can be explained by high electrophilicity of trichloroacetonitrile ( Fig. 3). At the first stage, ammonia reacts with CN bond to form amidine A as an intermediate. The subsequent reaction of A with second molecule of trichloroacetonitrile gives B. And finally, B reacts with CuCl 2 resulting in the copper(II) complex I in a high yield. We believe that Cu 2+ is formed by oxidation of Cu 1+ with CCl3CN as it was confirmed previously for catalytic olefination reaction.
The structure of the title compound I, C 8 H 4 N 6 Cl 12 Cu, was unambigouosly established by X-ray diffraction study (Fig.   4). The compound I crystallizes in the triclinic space group P-1 and there is a crystallographically imposed inversion centre at the Cu atom of each molecule. The Cu atom has a square-planar coordination. The 1,3,5-triazapentadienyl ligands are also planar (r.m.s. deviation is 0.021 Å). However, the six-membered metallocycles deviate significantly from the planarity and have a sofa conformation with the Cu atom out of the plane of the 1,3,5-triazapentadienyl ligands by 0.246 (5) Å. Thus, the molecule of I consists of the three planar units adopting the staircase-like structure. The similar molecular conformation has been previously observed in the related compounds (Zhang et al., 2005;Igashira-Kamiyama et al., 2006;Figiel et al., 2010). Nevertheless, it is important to note that the analogous complexes can adopt the planar conformation also (Boča et al., 1996;Kajiwara et al., 2002;Zheng et al., 2007). The ipso-C atoms of the CCl 3substituents are slightly out of the 1,3,5-triazapentadienyl planes by 0.149 (6) and -0.106 (6) Å. The CCl 3 -groups of each 1,3,5-triazapentadienyl ligand are practically in the energetically favorable eclipsed mutual conformation.

Experimental
A solution of trichloroacetonitrile (7.3 ml) in DMSO (15 ml) was dropped to a mixture of aqueous ammonia (5 ml) and freshly purified copper monochloride (0.3 g) during 3 min. upon keeping of the room temperature by the cooling on water-bath. The reaction mixture was stirred for 4 h. At the end of the reaction, the mixture was washed with water (150 ml) and filtered off. The formed product was re-crystallized from aqueous ethanol to give 1.47 g of red crystals of I.

Refinement
The hydrogen atoms were placed in calculated positions with N-H = 0.86 Å and refined in the riding model with fixed isotropic displacement parameters [U iso (H) = 1.2U eq (N)].

Figure 1
New catalytic olefination reaction as a general method for the preparation of alkenes; X and Y are H, Hal, CHal 3 , CN.  The stage-to-stage reaction mechanism of the formation of I.

Figure 4
Molecular structure of I with the atom numbering scheme. Displacement ellipsoids are shown at the 50% probability level. H atoms are presented as small spheres of arbitrary radius. Symmetry code: (i) -x, -y + 2, -z + 2.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.18 e Å −3 Δρ min = −0.85 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.