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Volume 68 
Part 9 
Pages m251-m254  
September 2012  

Received 17 July 2012
Accepted 23 July 2012
Online 1 August 2012

The weakly coordinating perchlorate group in bis(N,N'-dimethylethylenediamine-[kappa]2N,N')bis(perchlorato-[kappa]O)copper(II) studied at 100, 250 and 400 K

aInstitut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany, and bFaculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Polizu 1, RO-011061 Bucharest, Romania
Correspondence e-mail: ullrich.englert@ac.rwth-aachen.de

The crystal structure of the title compound, [Cu(ClO4)2(C4H12N2)2], (I), is reported at 100, 250 and 400 K. The CuII cation in this complex is coordinated in a distorted octahedral mode characteristic of Jahn-Teller systems. The coordination of the perchlorate ligands via longer, and presumably weaker, axial Cu-O distances varies significantly as a function of temperature. One of the Cu-O distances increases between 100 and 250 K, and one of the Cu-O-Cl angles expands between 250 and 400 K. At all temperatures, the complex forms a two-dimensional N-H...O hydrogen-bond network in the (001) plane.

Comment

The perchlorate group (ClO4-) represents a rather weakly coordinating anion (Pascal & Favier, 1998[Pascal, J.-L. & Favier, F. (1998). Coord. Chem. Rev. 178-180, 865-902.]). A search of the Cambridge Structural Database (CSD; Version 5.33 of November 2011, including updates until May 2012; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]) gave 10 249 error-free entries without disorder which contain one or more perchlorate anions and at least one metal atom; 1205 entries (11.8%) showed at least one perchlorate bonded to the metal. In an attempt to identify suitable cations for the coordination of weak ligands (Serb et al., 2007[Serb, M.-D., Calmuschi-Cula, B., Dumitru, F., Englert, U. & Guran, C. (2007). Acta Cryst. E63, m1484-m1486.]; Schnitzler et al., 2010[Schnitzler, S., Merkens, C., Wang, R., Wang, Y., Kalf, I. & Englert, U. (2010). Acta Cryst. A66, s270-s271.]), we envisaged CuII as a good candidate. This cation is a textbook example of Jahn-Teller distortion (Atkins et al., 2009[Atkins, P. W., Overton, T., Rourke, J., Weller, M. & Armstrong, F. (2009). Inorganic Chemistry, 5th ed. Oxford University Press.]) and we presumed that the more distant vertices in the coordination polyhedron might be more readily accessible to weakly coordinating groups. A CSD search confirmed this simple idea: 581 entries, corresponding to a higher fraction of 18.1%, featured a coordinated perchlorate, out of a total of 3213 error-free and undisordered entries with at least one CuII cation and one perchlorate in the structure. 204 structures showed (almost exclusively trans) geometries with two coordinated perchlorate groups. In this contribution, we report the influence of temperature on the crystal structure of a compound in that category.

[Scheme 1]

For the title compound, (I)[link], the lattice parameters and space group at ambient temperature, but not the atomic coordinates, had previously been determined by Näsänen et al. (1966[Näsänen, R., Virtamo, I. & Korvenranta, J. (1966). Suom. Kemistil. B, 39, 1-2.]) (CSD refcode ZZZHVW) based on Weissenberg photographs. Complex (I)[link] features four N-donor atoms in the equatorial plane of an elongated pseudo-octahedron and shows two longer, and presumably weaker, bonds between the CuII centre and the symmetrically independent perchlorate anions. In the present work, intensity data were collected at 100, 250 and 400 K, and are denoted data sets (Ia), (Ib) and (Ic), respectively. The resulting displacement ellipsoid plots are provided in Figs. 1[link]-3[link][link].

The intramolecular distances and angles at 100 K are unexceptional. Packing in this solid is dominated by classical intermolecular N-H...O hydrogen bonding, with N...O > 3 Å; a two-dimensional network is formed in the ab plane (see Fig. 4[link]). The hydrogen-bond geometry has been compiled in Tables 1[link] [for (Ia)] and 2[link] [for (Ib)].

The main focus of this contribution is the effect of temperature on perchlorate coordination. In this context, two observations merit discussion. Firstly, comparison of the structures at 100 and 250 K, i.e. (Ia) and (Ib), shows only one significant difference, namely an increase in the Cu1-O1 distance (Table 3[link]). In view of the disorder and the more elevated standard uncertainties in (Ic), the results obtained at the highest temperature should not be overinterpreted. Secondly, the weak perchlorate coordination is also reflected in the Cl1...Cl2 distances at different temperatures (Table 4[link]); (Ia) and (Ib) consistently show two different Cu-O-Cl angles, whereas both angles are large in the case of (Ic), resulting in a significantly longer Cl1...Cl2 separation. Both these observations lead to the conclusion that the increase in temperature is sufficient to trigger a significant change in the coordination of the weak perchlorate ligand.

[Figure 1]
Figure 1
The molecular structure of (Ia) at 100 K, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2]
Figure 2
The molecular structure of (Ib) at 250 K, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms have been omitted or clarity.
[Figure 3]
Figure 3
The molecular structure of (Ic) at 400 K, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms have been omitted for clarity. Atoms of the chelating ligand associated with N1 and N2 and of the perchlorate ligand associated with Cl1 refer to the major disorder component. For clarity, the corresponding minor components have not been shown.
[Figure 4]
Figure 4
The hydrogen-bond network in the ab plane in (Ia).

Experimental

Compound (I)[link] was prepared according to the procedure of Akitsu & Einaga (2004[Akitsu, T. & Einaga, Y. (2004). Acta Cryst. C60, m162-m164.]) by adding N,N'-dimethylethylenediamine (0.176 g, 2.00 mmol) dropwise to a methanol solution (20 ml) of Cu(ClO4)2·6H2O (0.375 g, 1.01 mmol) at room temperature (yield 87.7%). Violet plates suitable for single-crystal X-ray diffraction were obtained after 2 d by diffusion between solutions of both reactants in methanol at room temperature. Elemental analysis calculated (%): C 21.90, H 5.51, N 12.77; found (%): C 21.95, H 5.63, N 12.73.

(Ia) at 100 K

Crystal data
  • [Cu(ClO4)2(C4H12N2)2]

  • Mr = 438.75

  • Monoclinic, C c

  • a = 8.5395 (17) Å

  • b = 13.543 (3) Å

  • c = 14.743 (4) Å

  • [beta] = 95.358 (3)°

  • V = 1697.6 (6) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 1.65 mm-1

  • T = 100 K

  • 0.19 × 0.11 × 0.03 mm

Data collection
  • Bruker D8 goniometer with a SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2004[Bruker (2004). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.745, Tmax = 0.952

  • 9912 measured reflections

  • 3488 independent reflections

  • 3137 reflections with I > 2[sigma](I)

  • Rint = 0.055

Refinement
  • R[F2 > 2[sigma](F2)] = 0.037

  • wR(F2) = 0.075

  • S = 0.99

  • 3488 reflections

  • 224 parameters

  • 8 restraints

  • H atoms treated by a mixture of independent and constrained refinement

  • [Delta][rho]max = 0.45 e Å-3

  • [Delta][rho]min = -0.38 e Å-3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), with 1739 Friedel pairs

  • Flack parameter: 0.004 (14)

Table 1
Hydrogen-bond geometry (Å, °) (Ia) at 100 K

D-H...A D-H H...A D...A D-H...A
N1-H1...O4i 0.82 (3) 2.23 (3) 3.041 (5) 167 (4)
N2-H2...O3ii 0.81 (3) 2.34 (4) 3.133 (5) 168 (4)
N3-H3...O4 0.81 (3) 2.49 (3) 3.138 (5) 139 (3)
N3-H3...O7iii 0.81 (3) 2.56 (3) 3.071 (5) 123 (4)
N4-H4...O8iv 0.82 (3) 2.53 (4) 3.200 (5) 139 (3)
Symmetry codes: (i) [x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]; (ii) [x-{\script{1\over 2}}, y+{\script{1\over 2}}, z]; (iii) [x-{\script{1\over 2}}, y-{\script{1\over 2}}, z]; (iv) [x+{\script{1\over 2}}], [y-{\script{1\over 2}}, z].

(Ib) at 250 K

Crystal data
  • [Cu(ClO4)2(C4H12N2)2]

  • Mr = 438.75

  • Monoclinic, C c

  • a = 8.5966 (14) Å

  • b = 13.655 (2) Å

  • c = 14.966 (3) Å

  • [beta] = 95.533 (4)°

  • V = 1748.5 (5) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 1.60 mm-1

  • T = 250 K

  • 0.19 × 0.11 × 0.03 mm

Data collection
  • Bruker D8 goniometer with a SMART APEX CCD area detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2004[Bruker (2004). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.751, Tmax = 0.954

  • 10331 measured reflections

  • 3607 independent reflections

  • 2853 reflections with I > 2[sigma](I)

  • Rint = 0.064

Refinement
  • R[F2 > 2[sigma](F2)] = 0.047

  • wR(F2) = 0.103

  • S = 0.99

  • 3607 reflections

  • 224 parameters

  • 8 restraints

  • H atoms treated by a mixture of independent and constrained refinement

  • [Delta][rho]max = 0.42 e Å-3

  • [Delta][rho]min = -0.29 e Å-3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), with 1793 Friedel pairs

  • Flack parameter: 0.011 (19)

Table 2
Hydrogen-bond geometry (Å, °) for (Ib) at 250 K

D-H...A D-H H...A D...A D-H...A
N1-H1...O4i 0.82 (5) 2.27 (5) 3.068 (6) 163 (5)
N2-H2...O3ii 0.83 (5) 2.33 (5) 3.149 (9) 167 (5)
N3-H3...O4 0.83 (4) 2.49 (4) 3.211 (7) 147 (5)
N3-H3...O7iii 0.83 (4) 2.67 (5) 3.136 (7) 117 (4)
N4-H4...O8iv 0.82 (5) 2.68 (6) 3.287 (7) 132 (5)
Symmetry codes: (i) [x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]; (ii) [x-{\script{1\over 2}}, y+{\script{1\over 2}}, z]; (iii) [x-{\script{1\over 2}}, y-{\script{1\over 2}}, z]; (iv) [x+{\script{1\over 2}}, y-{\script{1\over 2}}, z].

(Ic) at 400 K

Crystal data
  • [Cu(ClO4)2(C4H12N2)2]

  • Mr = 438.75

  • Monoclinic, C c

  • a = 8.731 (3) Å

  • b = 13.824 (5) Å

  • c = 15.314 (6) Å

  • [beta] = 94.866 (9)°

  • V = 1841.7 (12) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 1.52 mm-1

  • T = 400 K

  • 0.32 × 0.10 × 0.04 mm

Data collection
  • Bruker D8 goniometer with a SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2004[Bruker (2004). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.643, Tmax = 0.942

  • 9966 measured reflections

  • 3479 independent reflections

  • 2156 reflections with I > 2[sigma](I)

  • Rint = 0.088

Refinement
  • R[F2 > 2[sigma](F2)] = 0.075

  • wR(F2) = 0.207

  • S = 1.01

  • 3479 reflections

  • 210 parameters

  • 69 restraints

  • H-atom parameters constrained

  • [Delta][rho]max = 0.86 e Å-3

  • [Delta][rho]min = -0.37 e Å-3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), with 1702 Friedel pairs

  • Flack parameter: 0.03 (4)

Table 3
Selected geometric parameters (Å, °) for the three determinations

  (Ia) (Ib) (Ic)
Cu1-N1 2.026 (3) 2.031 (4) 2.027 (11)
Cu1-N2 2.026 (4) 2.041 (5) 2.045 (11)
Cu1-N3 2.035 (3) 2.027 (5) 2.020 (9)
Cu1-N4 2.051 (4) 2.038 (5) 2.038 (10)
Cu1-O1 2.470 (3) 2.514 (5) 2.490 (10)
Cu1-O5 2.496 (3) 2.513 (5) 2.546 (11)
       
N1-Cu1-N2 85.66 (14) 85.21 (18) 85.2 (4)
N2-Cu1-N3 93.85 (13) 94.19 (18) 95.4 (4)
N1-Cu1-N3 174.88 (15) 176.57 (19) 178.4 (4)
N2-Cu1-N4 177.28 (16) 177.3 (2) 178.1 (4)
N1-Cu1-N4 95.09 (15) 95.34 (19) 94.9 (4)
O1-Cu1-O5 173.07 (10) 173.27 (18) 178.6 (5)

Table 4
Comparison of the perchlorate coordination in (Ia), (Ib) and (Ic) (Å, °)

  Cl1...Cl2 Cu1-O1-Cl1 Cu1-O5-Cl2
(Ia) 7.459 (2) 129.63 (18) 172.3 (2)
(Ib) 7.553 (2) 135.6 (4) 176.0 (3)
(Ic) 7.698 (5) 164.9 (10) 178.2 (9)

H atoms attached to N atoms in (Ia) and (Ib) were refined with Uiso(H) = 1.2Ueq(N) and with similarity restraints applied to the N-H distances. H atoms attached to N atoms in (Ic) and all other H atoms were introduced in their idealized positions and treated as riding, with methyl C-H = 0.98 Å for (Ia), 0.97 Å for (Ib) and 0.96 Å for (Ic), and with Uiso(H) = 1.5Ueq(C); methylene C-H = 0.99 Å for (Ia), 0.98 Å for (Ib) and 0.97 Å for (Ic), and with Uiso(H) = 1.2Ueq(C); N-H = 0.91 Å for (Ic) and Uiso(H) = 1.2Ueq(N).

Data set (Ic) was collected at 400 K. At this temperature, the displacement parameters indicate the pronounced mobility of all ligands in the complex. Obvious disorder was encountered in one of the perchlorate anions and in an ethylenediamine ligand. Split positions were refined for the atoms of the chelating ligand associated with N1 and N2 and for those of the perchlorate ligand associated with Cl1. Site occupancies for the alternative orientations were refined, and the sum of these occupancies was constrained to unity. The occupancies for the major conformations amounted to 0.67(2) in the disordered dimethylethylenediamine and to 0.53(2) in the disordered perchlorate ligand. All atom sites with fractional occupancies were assigned isotropic displacement parameters. These displacement parameters, and the distances and angles in the alternative conformations, were restrained to similarity, resulting in a total of 69 restraints. In (Ic), the occurrence of intensities with I(obs) >> I(calc) indicated nonmerohedral twinning (180° rotation about a*); PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) was used to generate an expanded set of intensity data in which a small fraction (225 out of 3479 reflections) was assigned as overlapped with contributions from a second smaller domain with a volume fraction of 0.348 (10).

For all determinations, data collection: SMART (Bruker, 2001[Bruker (2001). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-Plus (Bruker, 1999[Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: SHELXL97.


Supplementary data for this paper are available from the IUCr electronic archives (Reference: SK3443 ). Services for accessing these data are described at the back of the journal.


References

Akitsu, T. & Einaga, Y. (2004). Acta Cryst. C60, m162-m164.  [CSD] [CrossRef] [details]
Allen, F. H. (2002). Acta Cryst. B58, 380-388.  [ISI] [CrossRef] [details]
Atkins, P. W., Overton, T., Rourke, J., Weller, M. & Armstrong, F. (2009). Inorganic Chemistry, 5th ed. Oxford University Press.
Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.
Bruker (2001). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.
Bruker (2004). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
Flack, H. D. (1983). Acta Cryst. A39, 876-881.  [CrossRef] [details]
Näsänen, R., Virtamo, I. & Korvenranta, J. (1966). Suom. Kemistil. B, 39, 1-2.
Pascal, J.-L. & Favier, F. (1998). Coord. Chem. Rev. 178-180, 865-902.  [ISI] [CrossRef] [ChemPort]
Schnitzler, S., Merkens, C., Wang, R., Wang, Y., Kalf, I. & Englert, U. (2010). Acta Cryst. A66, s270-s271.  [CrossRef] [details]
Serb, M.-D., Calmuschi-Cula, B., Dumitru, F., Englert, U. & Guran, C. (2007). Acta Cryst. E63, m1484-m1486.  [CSD] [CrossRef] [details]
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.  [CrossRef] [details]
Spek, A. L. (2009). Acta Cryst. D65, 148-155.  [ISI] [CrossRef] [details]


Acta Cryst (2012). C68, m251-m254   [ doi:10.1107/S0108270112033318 ]