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The compound reported as tetra-μ-nitro­aminato-bis­[aqua­copper(II)] [Öztürk et al. (2003). Acta Cryst. E59, i107–i109] is shown to be tetra-μ-acetato-bis­[aqua­copper(II)], [Cu2(C2H3O2)4(H2O)2], based on a new refinement using the original reflection data.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803017331/cf6277sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803017331/cf6277Isup2.hkl
Contains datablock I

CCDC reference: 222792

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.006 Å
  • R factor = 0.048
  • wR factor = 0.096
  • Data-to-parameter ratio = 16.2

checkCIF/PLATON results

No syntax errors found



Alert level C PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low ..... 0.99
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 1 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 0 ALERT type 2 Indicator that the structure model may be wrong or deficient 1 ALERT type 3 Indicator that the structure quality may be low 0 ALERT type 4 Improvement, methodology, query or suggestion

Comment top

The structure of a centrosymmetric binuclear copper(II) complex described as tetra-µ-nitroaminato-bis[aquacopper(II)], [(H2NNO2)2Cu(H2O)]2, has recently been reported (Öztürk et al., 2003). Our interest in this material was kindled by the fact that, while the coordinated water molecule acts as a double donor in O—H···O hydrogen bonds, neither of the supposed amino groups participates in the hydrogen bonding. We note that no elemental analysis was reported for this complex and that identification as a nitramine derivative was based solely on the IR spectrum. We note further that nitramine H2NNO2 is a neutral compound, so that the description of the neutral complex in question as a copper(II) complex of nitramine cannot possibly be correct. Moreover, the reported N—N distances in this complex [1.505 (7) and 1.477 (6) Å] are both very long for bonds of this type. In 1-nitroindazole, for example, the N—NO2 distance is 1.336 (1) Å (Zaleski et al., 2001); on the other hand, such distances are typical of C—CO2 distances in carboxylate anions.

We report here that the material described as a nitramine complex (Öztürk et al., 2003) is, in fact, the well known tetra-µ-acetato-bis[aquacopper(II)], (I), whose structure has been extensively documented (van Niekerk & Schoening, 1953; de Meester et al., 1973; Brown & Chidambaram, 1973; Kita et al., 1992; Shamuratov et al., 1994). We base this diagnosis on (a) the unit-cell dimensions and space group, identical with those reported earlier; (b) the method of production, where an unidentified copper complex, obtained adventitiously following decomposition of a substituted triazolone, intended to act as a ligand, but containing no nitro group or indeed any N—O bonds, was recrystallized from hot glacial acetic acid, i.e. conditions in which nitramine readily undergoes decomposition to nitrous oxide N2O (Stedman, 1979); and (c) a new refinement based upon the original reflection data, but using the correct composition C8H16Cu2O10 (Fig. 1), rather than the erroneous formulation H12Cu2N8O10. This new refinement gave a lower R factor, viz. 0.048 as opposed to the 0.051 obtained using the same data set and the wrong composition, and detailed scrutiny of an extensive series of difference-map sections showed plainly the presence of disordered methyl groups, both modelled using six sites with 0.5 occupancy each, rather than amino groups. Similar scrutiny of difference-map sections based on the original refinement model allowed us to reject definitively the presence of NH2 groups. The C—C and C—O distances obtained (Table 1), while essentially the same as those reported as N—N and N—O distances, agree with those found in previous determinations of the structure of this acetate complex, as do the hydrogen bonds (Table 2).

We conclude that the identification reported for this material by Öztürk et al. (2003), in terms of both the chemical composition and the X-ray structure, is incorrect.

Refinement top

The refinement of the title compound employed the data associated with the publication of Öztürk et al. (2003). The coordinates were adjusted such that the asymmetric unit now forms a connected set, with the dimeric complex centred at (1/2, 1/2, 1/2). The two water H atoms were clearly visible in a difference map and the O—H distances were restrained to 0.84 (4) Å during subsequent refinement. The H atoms of the two independent methyl groups were clearly disordered and each group was modelled using six sites of 0.5 occupancy and a constrained common C—H distance of 0.99 Å.

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek 2003); software used to prepare material for publication: manual editing of cif.

Figures top
[Figure 1] Fig. 1. The molecule of compound (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level, and the atoms marked 'a' are at the symmetry position (1 − x, 1 − y, 1 − z).
Tetra-µ-acetato-bis[aquacopper(II)] top
Crystal data top
[Cu2(C2H3O2)4(H2O)2]F(000) = 808
Mr = 399.31Dx = 1.905 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 2792 reflections
a = 13.1677 (18) Åθ = 2.9–28.3°
b = 8.5716 (12) ŵ = 3.12 mm1
c = 13.8499 (19) ÅT = 293 K
β = 117.024 (2)°Slab, blue
V = 1392.5 (3) Å30.36 × 0.28 × 0.22 mm
Z = 4
Data collection top
Siemens SMART CCD area-detector
diffractometer
1624 independent reflections
Radiation source: fine-focus sealed tube1391 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.030
Detector resolution: 8.33 pixels mm-1θmax = 28.3°, θmin = 3.0°
ω scansh = 1715
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
k = 1111
Tmin = 0.368, Tmax = 0.504l = 1418
3874 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.048Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.096H atoms treated by a mixture of independent and constrained refinement
S = 1.36 w = 1/[σ2(Fo2) + (0.0294P)2 + 2.7917P]
where P = (Fo2 + 2Fc2)/3
1624 reflections(Δ/σ)max < 0.001
100 parametersΔρmax = 0.55 e Å3
2 restraintsΔρmin = 0.62 e Å3
Crystal data top
[Cu2(C2H3O2)4(H2O)2]V = 1392.5 (3) Å3
Mr = 399.31Z = 4
Monoclinic, C2/cMo Kα radiation
a = 13.1677 (18) ŵ = 3.12 mm1
b = 8.5716 (12) ÅT = 293 K
c = 13.8499 (19) Å0.36 × 0.28 × 0.22 mm
β = 117.024 (2)°
Data collection top
Siemens SMART CCD area-detector
diffractometer
1624 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1391 reflections with I > 2σ(I)
Tmin = 0.368, Tmax = 0.504Rint = 0.030
3874 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0482 restraints
wR(F2) = 0.096H atoms treated by a mixture of independent and constrained refinement
S = 1.36Δρmax = 0.55 e Å3
1624 reflectionsΔρmin = 0.62 e Å3
100 parameters
Special details top

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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 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 (Å2) top
xyzUiso*/UeqOcc. (<1)
Cu10.54996 (3)0.58405 (5)0.45509 (3)0.01663 (14)
O10.5952 (2)0.3795 (3)0.4257 (2)0.0291 (6)
O20.5077 (2)0.2356 (3)0.5000 (2)0.0298 (6)
O30.6834 (2)0.5889 (3)0.6002 (2)0.0256 (5)
O40.6004 (2)0.4400 (3)0.6757 (2)0.0255 (6)
O50.6245 (3)0.7081 (4)0.3672 (2)0.0336 (7)
H500.677 (3)0.774 (4)0.385 (4)0.043 (10)*
H510.616 (4)0.664 (6)0.310 (2)0.043 (10)*
C10.5670 (3)0.2526 (5)0.4492 (3)0.0245 (8)
C20.6035 (4)0.1045 (5)0.4153 (4)0.0376 (10)
H2A0.60850.02180.46410.056*0.50
H2B0.67660.11990.41730.056*0.50
H2C0.54850.07740.34300.056*0.50
H2D0.61390.12420.35220.056*0.50
H2E0.54580.02620.39900.056*0.50
H2F0.67390.06860.47330.056*0.50
C30.6825 (3)0.5210 (5)0.6804 (3)0.0210 (7)
C40.7834 (4)0.5372 (6)0.7880 (3)0.0400 (11)
H4A0.76620.49420.84290.060*0.50
H4B0.80250.64550.80290.060*0.50
H4C0.84680.48210.78780.060*0.50
H4D0.84410.58700.77950.060*0.50
H4E0.80780.43570.81950.060*0.50
H4F0.76350.59910.83470.060*0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0130 (2)0.0199 (2)0.0166 (2)0.00141 (18)0.00638 (15)0.00039 (18)
O10.0277 (14)0.0263 (15)0.0377 (16)0.0006 (11)0.0187 (13)0.0064 (12)
O20.0318 (14)0.0210 (15)0.0402 (15)0.0032 (11)0.0194 (13)0.0048 (12)
O30.0186 (11)0.0346 (14)0.0218 (12)0.0030 (11)0.0077 (10)0.0020 (12)
O40.0174 (12)0.0327 (16)0.0212 (12)0.0056 (10)0.0042 (10)0.0032 (11)
O50.0397 (16)0.0417 (18)0.0286 (15)0.0206 (14)0.0235 (14)0.0112 (13)
C10.0147 (15)0.030 (2)0.0262 (18)0.0024 (14)0.0068 (14)0.0051 (16)
C20.038 (2)0.030 (2)0.044 (2)0.0084 (18)0.018 (2)0.0140 (19)
C30.0153 (15)0.0252 (17)0.0187 (16)0.0019 (13)0.0044 (14)0.0016 (14)
C40.0252 (19)0.058 (3)0.024 (2)0.0124 (19)0.0002 (17)0.0020 (19)
Geometric parameters (Å, º) top
Cu1—O2i1.945 (3)O5—H510.84 (4)
Cu1—O11.953 (3)C2—H2A0.96
Cu1—O31.979 (3)C2—H2B0.96
Cu1—O4i1.996 (2)C2—H2C0.96
Cu1—O52.159 (3)C2—H2D0.96
Cu1—Cu1i2.6157 (8)C2—H2E0.96
C1—C21.506 (5)C2—H2F0.96
O1—C11.239 (5)C4—H4A0.96
O2—C11.275 (5)C4—H4B0.96
C3—C41.486 (5)C4—H4C0.96
O3—C31.260 (4)C4—H4D0.96
O4—C31.261 (4)C4—H4E0.96
O5—H500.84 (4)C4—H4F0.96
O2i—Cu1—O1168.69 (12)C1—C2—H2E109.5
O2i—Cu1—O387.37 (12)H2A—C2—H2E56.3
O1—Cu1—O390.95 (11)H2B—C2—H2E141.1
O2i—Cu1—O4i90.11 (12)H2C—C2—H2E56.3
O1—Cu1—O4i89.36 (11)H2D—C2—H2E109.5
O3—Cu1—O4i168.63 (10)C1—C2—H2F109.5
O2i—Cu1—O597.60 (12)H2A—C2—H2F56.3
O1—Cu1—O593.71 (12)H2B—C2—H2F56.3
O3—Cu1—O598.07 (11)H2C—C2—H2F141.1
O4i—Cu1—O593.25 (11)H2D—C2—H2F109.5
O2i—Cu1—Cu1i86.10 (9)H2E—C2—H2F109.5
O1—Cu1—Cu1i82.62 (9)O3—C3—O4124.1 (3)
O3—Cu1—Cu1i86.29 (8)O3—C3—C4118.6 (3)
O4i—Cu1—Cu1i82.48 (8)O4—C3—C4117.3 (3)
O5—Cu1—Cu1i174.37 (8)C3—C4—H4A109.5
C1—O1—Cu1125.2 (2)C3—C4—H4B109.5
C1—O2—Cu1i120.7 (3)H4A—C4—H4B109.5
C3—O3—Cu1121.7 (2)C3—C4—H4C109.5
C3—O4—Cu1i125.2 (2)H4A—C4—H4C109.5
Cu1—O5—H50134 (4)H4B—C4—H4C109.5
Cu1—O5—H51114 (4)C3—C4—H4D109.5
H50—O5—H51109 (5)H4A—C4—H4D141.1
O1—C1—O2125.3 (4)H4B—C4—H4D56.3
O1—C1—C2118.8 (3)H4C—C4—H4D56.3
O2—C1—C2115.9 (4)C3—C4—H4E109.5
C1—C2—H2A109.5H4A—C4—H4E56.3
C1—C2—H2B109.5H4B—C4—H4E141.1
H2A—C2—H2B109.5H4C—C4—H4E56.3
C1—C2—H2C109.5H4D—C4—H4E109.5
H2A—C2—H2C109.5C3—C4—H4F109.5
H2B—C2—H2C109.5H4A—C4—H4F56.3
C1—C2—H2D109.5H4B—C4—H4F56.3
H2A—C2—H2D141.1H4C—C4—H4F141.1
H2B—C2—H2D56.3H4D—C4—H4F109.5
H2C—C2—H2D56.3H4E—C4—H4F109.5
O2i—Cu1—O1—C17.0 (8)Cu1i—Cu1—O3—C30.2 (3)
O3—Cu1—O1—C188.3 (3)Cu1—O1—C1—O22.8 (5)
O4i—Cu1—O1—C180.3 (3)Cu1—O1—C1—C2176.5 (3)
O5—Cu1—O1—C1173.5 (3)Cu1i—O2—C1—O11.4 (5)
Cu1i—Cu1—O1—C12.2 (3)Cu1i—O2—C1—C2178.0 (3)
O2i—Cu1—O3—C386.5 (3)Cu1—O3—C3—O42.9 (5)
O1—Cu1—O3—C382.3 (3)Cu1—O3—C3—C4176.6 (3)
O4i—Cu1—O3—C39.2 (7)Cu1i—O4—C3—O35.5 (5)
O5—Cu1—O3—C3176.2 (3)Cu1i—O4—C3—C4174.0 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H50···O3ii0.84 (4)2.12 (4)2.931 (4)166 (5)
O5—H51···O4iii0.84 (4)1.99 (4)2.825 (4)179 (5)
Symmetry codes: (ii) x+3/2, y+3/2, z+1; (iii) x, y+1, z1/2.

Experimental details

Crystal data
Chemical formula[Cu2(C2H3O2)4(H2O)2]
Mr399.31
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)13.1677 (18), 8.5716 (12), 13.8499 (19)
β (°) 117.024 (2)
V3)1392.5 (3)
Z4
Radiation typeMo Kα
µ (mm1)3.12
Crystal size (mm)0.36 × 0.28 × 0.22
Data collection
DiffractometerSiemens SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.368, 0.504
No. of measured, independent and
observed [I > 2σ(I)] reflections
3874, 1624, 1391
Rint0.030
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.048, 0.096, 1.36
No. of reflections1624
No. of parameters100
No. of restraints2
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.55, 0.62

Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek 2003), manual editing of cif.

Selected bond lengths (Å) top
C1—C21.506 (5)C3—C41.486 (5)
O1—C11.239 (5)O3—C31.260 (4)
O2—C11.275 (5)O4—C31.261 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H50···O3i0.84 (4)2.12 (4)2.931 (4)166 (5)
O5—H51···O4ii0.84 (4)1.99 (4)2.825 (4)179 (5)
Symmetry codes: (i) x+3/2, y+3/2, z+1; (ii) x, y+1, z1/2.
 

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