Bis{(E)-3-[2-(hydroxyimino)propanamido]-2,2-dimethylpropan-1-aminium} bis[μ-(E)-N-(3-amino-2,2-dimethylpropyl)-2-(hydroxyimino)propanamido(2−)]bis{[(E)-N-(3-amino-2,2-dimethylpropyl)-2-(hydroxyimino)propanamide]copper(II)} bis((E)-{3-[2-(hydroxyimino)propanamido]-2,2-dimethylpropyl}carbamate) aceton

The reaction between copper(II) nitrate and (E)-N-(3-amino-2,2-dimethylpropyl)-2-(hydroxyimino)propanamide led to the formation of the dinuclear centrosymmetric copper(II) title complex, (C8H18N3O2)2[Cu2(C8H15N3O2)2(C8H17N3O2)2](C9H16N3O4)2·2CH3CN, in which an inversion center is located at the midpoint of the Cu2 unit in the center of the neutral [Cu2(C8H15N3O2)2(C8H17N3O2)2] complex fragment. The Cu2+ ions are connected by two N—O bridging groups [Cu⋯Cu separation = 4.0608 (5) Å] while the CuII ions are five-coordinated in a square-pyramidal N4O coordination environment. The complex molecule co-crystallizes with two molecules of acetonitrile, two molecules of the protonated ligand (E)-3-[2-(hydroxyimino)propanamido]-2,2-dimethylpropan-1-aminium and two negatively charged (E)-{3-[2-(hydroxyimino)propanamido]-2,2-dimethylpropyl}carbamate anions, which were probably formed as a result of condensation between (E)-N-(3-amino-2,2-dimethylpropyl)-2-(hydroxyimino)propanamide and hydrogencarbonate anions. In the crystal, the complex fragment [Cu2(C8H15N3O2)2(C8H17N3O2)2] and the ion pair C8H18N3O2 +.C9H16N3O4 − are connected via an extended system of hydrogen bonds.

Amide derivatives of 2-hydroxyiminopropanoic acid have been widely used as versatile polynucleating ligands, in particular, for preparation of bi-and polynuclear complexes (Moroz et al., 2008(Moroz et al., , 2010 and metal complexes with efficient stabilization of unusually high oxidation states of 3d-metal ions like copper(III) and nickel(III) (Fritsky et al., 1998;Kanderal et al., 2005;Fritsky et al., 2006). Each dianion C 8 H 15 N 3 O 2 2is coordinated to a copper(II) ion Cu1 via three nitrogen atoms N1, N2, N3 (from the oxime, amide and amino groups, respectively) and through oxygen atom O1 from the N-O group to a second copper(II) ion Cu1′. The coordination environment of each copper ion is completed by the nitrogen atom N4 from the monodentately coordinated neutral ligand molecule C 8 H 17 N 3 O 2 , thus resulting N 4 O donor set of copper(II) ions. The bond distances between copper(II) ion and nitrogen atoms N1 -N4 vary from the 1.957 (2) Å to 2.041 (2) Å, while the Cu1 -O1 bond is longer (2.4417 (1) Å), that is a consequence of the Jahn -Teller distortion. The copper(II) ions in (I) are located in the distorted square-pyramidal coordination environment, what confirms with low value of τ parameter (τ = 0.27) (Addison et al., 1984) In both coordinated and non-coordinated ligands the oxime group is situated in the trans-position with respect to the amide group and anti-with respect to the amide carbonyl which was early shown in the structures of similiar compounds -amide derivatives of 2-hydroxyiminopropanoic acid (Skopenko et al., 1990;Onindo et al., 1995;Duda et al., 1997;Sliva et al., 1997). The C=N and N-O bond lengths in the oxime moiety are typical for 2-hydroxyiminopropanoic acid and its amide derivatives (Lampeka et al., 1989;Dvorkin et al., 1990aDvorkin et al., , 1990bDobosz et al., 1999;Mokhir et al., 2002).
The C-N and C-N bond lengths in the amine parts of the ligands are normal for aliphatic amines (Petrusenko et al., 1997).
The non-coordinated anions C 9 H 16 N 3 O 4in (I) possibly were formed due to the condensation processes between initial ligand C 8 H 17 N 3 O 2 and carbon dioxide, which could been captured from air. Capture of CO 2 from air and its following coordination or condensation with ligands in the complex composition is not rare (Kovbasyuk et al., 1997;Pavlishchuk et al., 2002;Nanda et al., 2006). In the crystal packing of (I) complex fragment [Cu 2 (C 8 H 15 N 3 O 2 ) 2 (C 8 H 17 N 3 O 2 ) 2 ] and the ion pair C 8 H 18 N 3 O 2 +. C 9 H 16 N 3 O 4are connected via extended system of hydrogen bonds. Almost all H atoms in hydroxy, amino and imino groups in I are included in the formation of hydrogen bonding.

Synthesis of the ligand C 8 H 17 N 3 O 2
A solution of the ethyl ester of 2-hydroxyiminopropanoic acid (13.1 g, 0.1 mol) in methanol (50 ml) was added to 1,3diamino-2,2-dimethylpropane (5.1 g, 5.9 ml, 0.05 mol) in methanol (25 ml). The obtained mixture was stirred at 60°C for 30 min and after that kept at room temperature for 72 h. The solution was dried by rotary evaporation, yielding an oily residue. Its subsequent treatment with a small amount of water resulted in a white powder which was collected, washed with cold water and air-dried. The resulting product is fairly soluble in alcohols and DMSO and poorly soluble in hot water. Yield: 15.1 g (81%

Refinement
The NH, NH 2 , NH 3 , and OH H atoms were located from the difference Fourier map but constrained to ride on their parent atom (U iso = 1.5 (parent atom)). Other H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.98-0.99 Å, and U iso = 1.2-1.5 U eq (parent atom). (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figure 1
ORTEP view of (I) with the atomic numbering scheme (thermal ellipsoids are drawn at the 50% probability level).

Figure 2
A view of the complete unit cell of the crystal structure of (I). Hydrogen atoms are omitted for clarity.

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. Symmetry codes: (i) −x+2, −y, −z+1; (ii) x, y+1, z; (iii) −x+2, −y, −z; (iv) x+1, y, z; (v) −x+1, −y+1, −z; (vi) −x+1, −y, −z.