catena-Poly[[[(diethylenetriamine-κ3 N,N′,N′′)copper(II)]-μ-cyanido-κ2 C:N] perchlorate]

The structure of the title salt, {[Cu(CN)(C4H13N3)]ClO4}n, is composed of copper-containing cations and perchlorate anions. The CuII atom shows a square-pyramidal coordination, with equatorial positions occupied by the cyanide C atom [Cu—C = 1.990 (3) Å] and the N atoms of the diethylenetriamine ligand (average Cu—N = 2.033 Å), while the axial position is occupied by the N atom of a c-glide-related cyanide group. The axial Cu—N distance of 2.340 (3) Å is longer than the equatorial distances, reflecting Jahn–Teller distortion. The CuII cations are linked by the cyanide groups into infinite chains along the c-axis direction. The refinement included a three-component disordered model for the perchlorate ion. Each minor site is stabilized by hydrogen bonds to N—H donors from four surrounding cations, while one O atom of the major perchlorate site forms hydrogen bonds to three of these cations.


Experimental
Crystal data [Cu(CN) (C 4  158 parameters H-atom parameters constrained Á max = 0.59 e Å À3 Á min = À0.35 e Å À3 Table 1 Selected bond lengths (Å ).  Data collection: locally modified program (Corfield, 1972); cell refinement: locally modified program (Corfield, 1972); data reduction: cell refinements and data reduction follow procedures in Corfield et al. (1967) and Corfield & Shore (1973); standard deviations of intensities include an ignorance factor (Busing & Levy, 1957b) set here to 0.06; program(s) used to solve structure: local superposition program (Corfield, 1972); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.  (Fig. 1), was originally prepared as a simple model for CNbinding to coppercontaining proteins, with the expectation that structural data would supplement information from infra-red studies on cyanide binding to the proteins. (Fager and Alben, 1972) The structure is reported now in light of current interest in cyanide-bridged copper polymers.
The crystal structure consists of cyanidodiethylenetriaminecopper(II) cations and perchlorate anions. The cyanide groups link c-glide related copper atoms to form infinite chains along the c axis, as shown in Fig. 2. The coordination of the copper atoms is square pyramidal, with the terdentate diethylenetriamine ligand and the carbon atom of the cyanide group in equatorial positions, and the nitrogen atom of a symmetry-related cyanide group in the axial position.
Atom O4 of the perchlorate group would occupy the sixth coordination site of the Cu II atom if the Cu-O4 distance of 2.956 (4) Å represented a chemical bond, making the copper atom octahedrally coordinated. Perchlorate anions rarely coordinate, however, and we prefer the square pyramidal designation, in view of the long Cu-O4 distance, and the displacement of the copper atom by 0.237 (1) Å towards the axial nitrogen atom and away from the perchlorate O4 atom.
Furthermore, the O4 atom has similar U eq values to the other perchlorate oxygen atoms, and is disordered in the same way, whereas bonding to the Cu atom would be expected to localize the atom O4.
The Cu-C-N angle at the cyanide carbon atom is close to linear, at 175.9 (3)°, but the C-N-Cu angle at the bridging cyanide nitrogen atom is 146.5 (2)°, significantly different from 180°. The C-N bond length is 1.139 (4) Å, similar to the terminal bond length of 1.129 Å in K 3 Cu(CN) 4 , (Roof et al., 1968).
Two minor alternative orientations for the perchlorate anion were refined, related to the major orientation by rotation about the Cl-O2 bond, by 34° in one direction, and 25° in the other. (Fig. 3) Each minor site is stabilized by hydrogen bonds to N-H donors from four surrounding cations, while atom O3 of the major perchlorate site forms hydrogen bonds to three of these cations.

Experimental
The compound was prepared by addition of stoichiometric amounts of diethylenetriamine and potassium cyanide to a solution of copper (II)

Refinement
All 13 hydrogen atoms of the diethylenetriamine ligand were found unambiguously in a difference Fourier map, and were initially refined freely. In the final refinements, hydrogen atoms were constrained to idealized positions by SHELXL97.
The assignment of C and N atoms in the cyanide group was checked early in the analysis by carrying out a least-squares refinement with the N and C atoms of the cyanide group reversed. The weighted R factor increased significantly from 0.061 to 0.091. There is no evidence of disorder between the C and N atoms of the cyanide group.
Perchlorate ion disorder: Refinement of a single anisotropic perchlorate group converged successfully with wR2=0.1091 for all 1752 reflections. The thermal parameters indicated large librations about the Cl-O2 bond however, and difference Fourier maps indicated two minor alternative orientations for the perchlorate group.
After initial stringent constraints, the three orientations were refined freely, with common Cl and O2 atoms. The main orientation (O1-O4) was refined anisotropically, with an occupancy fixed at 70%. The two minor orientations (O1′-O4′) and (O1′′-O4′′) were given occupancy factors of 18% and 12% respectively, based upon heights found in difference Fourier maps. U values for O1′ and O1′′, O3′ and O3′′, and O4′ and O4′′ were constrained to be equal. This model reduced wR2 significantly from 0.1091 to 0.0847, with the addition of 22 new parameters.

catena-Poly[[[(diethylenetriamine-κ 3 N,N′,N′′)copper(II)]-µ-cyanido-κ 2 C:N] perchlorate]
Crystal data [Cu(CN) where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.59 e Å −3 Δρ min = −0.35 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0010 (2) 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (