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Volume 61 
Part 8 
Pages m1525-m1527  
August 2005  

Received 3 May 2005
Accepted 21 June 2005
Online 13 July 2005

Key indicators
Single-crystal X-ray study
T = 100 K
Mean [sigma](C-C) = 0.007 Å
Some non-H atoms missing,
Disorder in main residue
R = 0.089
wR = 0.255
Data-to-parameter ratio = 35.0
Details

Diethanolaminium cyclo-octa-[mu]2-fluoro-hexadeca-[mu]2-trimethylacetato-[kappa]32O:O'-heptachromium(III)nickel(II) ethyl acetate 0.5-solvate

aDepartment of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark, and bSchool of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, England
Correspondence e-mail: kre@chem.au.dk

The title compound, [N(C2H4OH)2H2][Cr7NiF8(C5H9O2)16]·0.5C4H8O2, is a heterometallic wheel templated by a protonated amino alcohol. It consists of an octagon of metal centres, with each edge of the octagon bridged by a single F- anion and two carboxylate groups. Each metal atom is octahedrally coordinated. The protonated amine molecule protrudes through the cavity of the ring, while a solvent ethyl acetate molecule fills up the vacant space between the ring anions. It appears that the one equivalent of Ni atoms is unevenly distributed among the eight metal sites.

Comment

Our recent report (Larsen, McInnes et al., 2003[Larsen, F. K., McInnes, E. J. L., El Mkami, H., Overgaard, J., Piligkos, S., Rajaraman, G., Rentschler, E., Smith, A. A., Smith, G. M., Boote, V., Jennings, M., Timco G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 101-105.]) of a series of octanuclear {Cr7M} heterometallic wheel-type complexes with the general formula [NR2H2][Cr7MF8(O2CCMe3)16] was the first report of anti-ferromagnetically coupled cyclic molecules that have a non-diamagnetic ground state. There has been considerable interest in such molecules for applications as diverse as olefin polymerization catalysis (Lassahn et al., 2004[Lassahn, P.-G., Lozan, V., Timco, G. A., Christian, P., Janiak C. & Winpenny, R. E. P. (2004). J. Catal. 222, 260-267.]), magnetic cooling (Affronte et al., 2004[Affronte, M., Ghirri, A., Carretta, S., Amoretti, G., Piligkos, S., Timco, G. A. & Winpenny, R. E. P. (2004). Appl. Phys. Lett. 84, 3468-3470.]) and quantum computing (Meier et al., 2003[Meier, F., Levy, J. & Loss, D. (2003). Phys. Rev. Lett. 90, 047901-1.]). They were synthesized using a secondary ammonium cation, [NR2H2]+, which is a protonated alkyl-chain secondary amine with R = CH3(CH2)n (e.g. n = 0-7). It acts as a template in the reaction of CrF3·4H2O with pivalic acid in the presence of a second divalent metal cation (M2+ = Ni, Co, Mn, Fe, Zn or Cd). This procedure gives {Cr7M} ring compounds in good yield (Larsen, Overgaard et al., 2003[Larsen, F. K., Overgaard, J., Parsons, S., Rentschler, E., Smith, A. A., Timco, G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 5978-5981.]; Larsen, McInnes et al., 2003[Larsen, F. K., McInnes, E. J. L., El Mkami, H., Overgaard, J., Piligkos, S., Rajaraman, G., Rentschler, E., Smith, A. A., Smith, G. M., Boote, V., Jennings, M., Timco G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 101-105.]). In each case, the amines are found to be hydrogen-bonded at the centre of the metal ring. The protonated N atoms are not involved in the packing of the molecules in the crystal structure, because they are accommodated completely in the cavity (void) of the wheels. However, it was found that the choice of R can influence the packing of the rings in the crystal structure, regardless of the solvent used for crystallization. For example, both short and very long alkyl chains lead to packing where the octanuclear wheels are coplanar (generally tetragonal or orthorhombic crystals), but for intermediate chain lengths (Et or nPr), monoclinic crystals are found, where the rings pack with an angle of ca 50° between the mean planes of neighbouring rings (Larsen, Overgaard et al., 2003[Larsen, F. K., Overgaard, J., Parsons, S., Rentschler, E., Smith, A. A., Timco, G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 5978-5981.]).

The purpose of this paper is to extend further our studies of heterometallic wheels, by the preparation and structural characterization of the new title complex, [N(CH2CH2OH)2H2][Cr7NiF8(O2CCMe3)16][C4H8O2]0.5, (I)[link]. Using a protonated secondary amino alcohol as a template, we wished to investigate the influence of the alcohol group on the accommodation of the amine group in the void of the wheel, and also how the -OH group might influence the packing of the anionic rings in the crystal structure. A further goal was to obtain a complex for the synthesis of further polymetallic cage complexes, using the two OH groups of the diethanolamine to bind to further metal centres.

[Scheme 1]

For five of the 16 bridging pivalate groups in (I)[link], two possible positions were located and refined for the tert-butyl methyl groups. The occupation factors for the major component of these five disordered pivalate groups, of which two are on either face, while one is on the edge of the circular ring molecule, are in the range 0.521 (10)-0.592 (9). For all pivalate groups, a restraint was imposed in order to maintain tetrahedral coordination of the CMe3 groups, and a common C-C bond length was restrained to 1.521 (1) Å.

Compound (I)[link] was crystallized from an ethyl acetate solution and a molecule of ethyl acetate is incorporated in the crystal structure. It is situated near a centre of symmetry and is disordered over two positions, with two of the atom positions coinciding. The protonated ethanolamine molecule appears to be disordered over three orientations in the void of the octagonal ring, with one major [0.444 (5)] and two minor [0.251 (5) and 0.302 (5)] orientations. The amine N atom of the main component sits significantly closer to one side of the ring than the other. The N...F distances vary systematically around the ring: N1...F1 = 3.104 (3), N1...F2 = 3.408 (3), N1...F3 = 3.730 (3), N1...F4 = 3.829 (3), N1...F5 = 3.557 (3), N1...F6 = 3.215 (3), N1...F7 = 2.878 (3) and N1...F8 = 2.855 (3) Å.

In the final cycles of refinement, all Cr/Ni atoms were refined using Cr scattering factors. The metal atoms on the side of the ring with the shorter N...F separations tend to have smaller values for their equivalent isotropic displacement parameters: Ueq(Cr1) = 0.0238 (1), Ueq(Cr2) = 0.0281 (1), Ueq(Cr3) = 0.0286 (1), Ueq(Cr4) = 0.0308 (1), Ueq(Cr5) = 0.0234 (1), Ueq(Cr6) = 0.0222 (1), Ueq(Cr7) = 0.0238 (1) and Ueq(Cr8) = 0.0257 (1) Å2. Since Ni has four more electrons than Cr, it is conceivable that the Cr atoms with lower Ueq values may have greater Ni occupancy, so there is an indication of an uneven distribution of Ni around the ring.

The O atoms of the ethanolamine molecule are found to have short distances to the same F atoms which are involved in the shortest N...F separation [O2A...F1 = 2.952 (3) and O2B...F8 = 2.933 (3) Å]. The minor disorder components of the ethanolammonium cation show short N...F distances to other F atoms than found for the major component and of similar lengths: N1C...F1 = 2.721 (3), N1C...F2 = 2.922 (3) and N1C...F8 = 2.939 (3) Å, and N1E...F6 = 2.837 (3), N1E...F7 = 2.940 (3) and N1E...F5 = 3.084 (3) Å.

[Figure 1]
Figure 1
A view of (I)[link], showing 50% displacement ellipsoids, with selected atoms labelled. Only one orientation is shown for the disorder components. Colour key: Cr/Ni green, F pink, O red, C grey, N blue. H atoms have been omitted.

Experimental

Compound (I)[link] was synthesized in approximately 65% yield in a similar way to the analogues reported earlier (Larsen, Overgaard et al., 2003[Larsen, F. K., Overgaard, J., Parsons, S., Rentschler, E., Smith, A. A., Timco, G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 5978-5981.]), except that the amine used was diethanolamine and the product was crystallized from ethyl acetate. Elemental analysis (dried sample), calculated for C84H156Cr7F8N1Ni1O34: Cr 15.83, Ni 2.55, C 43.89, H 6.84, N 0.61%; found: Cr 15.28, Ni 2.72, C 43.89, H 7.00, N 0.62%. ES-MS (2 THF/MeOH m/z): -2191 [Cr7NiF8(O2CCMe3)16], 2298 [M-], 2321 [M+Na]+.

Crystal data
  • (C4H12NO2)[Cr7NiF8(C5H9O2)16]·0.5C4H8O2

  • Mr = 2342.85

  • Monoclinic, P 21 /c

  • a = 24.9892 (15) Å

  • b = 16.6220 (9) Å

  • c = 30.8299 (19) Å

  • [beta] = 110.506 (3)°

  • V = 11994.4 (12) Å3

  • Z = 4

  • Dx = 1.294 Mg m-3

  • Mo K[alpha] radiation

  • Cell parameters from 9946 reflections

  • [theta] = 2.2-31.0°

  • [mu] = 0.78 mm-1

  • T = 100 (2) K

  • Block, green

  • 0.38 × 0.3 × 0.25 mm

Data collection
  • Bruker X8 APEX-II diffractometer

  • [varphi] and [omega] scans

  • Absorption correction: multi-scan(SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.])Tmin = 0.723, Tmax = 0.823

  • 209153 measured reflections

  • 38517 independent reflections

  • 28754 reflections with I > 2[sigma](I)

  • Rint = 0.035

  • [theta]max = 31.1°

  • h = -36 [rightwards arrow] 35

  • k = -23 [rightwards arrow] 24

  • l = -44 [rightwards arrow] 44

Refinement
  • Refinement on F2

  • R[F2 > 2[sigma](F2)] = 0.091

  • wR(F2) = 0.258

  • S = 1.04

  • 38517 reflections

  • 1066 parameters

  • H-atom parameters constrained

  • w = 1/[[sigma]2(Fo2) + (0.1134P)2 + 52.1149P] where P = (Fo2 + 2Fc2)/3

  • ([Delta]/[sigma])max = 0.006

  • [Delta][rho]max = 2.10 e Å-3

  • [Delta][rho]min = -1.17 e Å-3

Methyl H atoms were located in idealized positions, with C-H = 0.98 Å, and refined as riding, with the constraint Uiso(H) = 1.5Uiso(C). N-bound H atoms were located in idealized positions, with N-H = 0.92 Å, and refined as riding, with the constraint Uiso(H) = 1.2Uiso(N). The highest difference peak is 0.39 Å from H20C and the deepest difference hole is 0.51 Å from C28.

Data collection: APEX-II (Bruker-Nonius, 2004[Bruker-Nonius (2004). APEX-II and SAINT-Plus (Version 7.06a). Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-Plus (Bruker-Nonius, 2004[Bruker-Nonius (2004). APEX-II and SAINT-Plus (Version 7.06a). Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXL97 and SHELXS97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXL97 and SHELXS97. University of Göttingen, Germany.]); molecular graphics: SHELXL97; software used to prepare material for publication: enCIFer (Version 1.1; Allen et al., 2004[Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J. Appl. Cryst. 37, 335-338.]) and WinGX (Version 1.70.00; Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Acknowledgements

This work was supported by the INTAS (03-51-4532) and the EPSRC (UK).

References

Affronte, M., Ghirri, A., Carretta, S., Amoretti, G., Piligkos, S., Timco, G. A. & Winpenny, R. E. P. (2004). Appl. Phys. Lett. 84, 3468-3470. [CrossRef] [ChemPort]
Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J. Appl. Cryst. 37, 335-338. [details]
Bruker-Nonius (2004). APEX-II and SAINT-Plus (Version 7.06a). Bruker AXS Inc., Madison, Wisconsin, USA.
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838. [details]
Larsen, F. K., McInnes, E. J. L., El Mkami, H., Overgaard, J., Piligkos, S., Rajaraman, G., Rentschler, E., Smith, A. A., Smith, G. M., Boote, V., Jennings, M., Timco G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 101-105.
Larsen, F. K., Overgaard, J., Parsons, S., Rentschler, E., Smith, A. A., Timco, G. A. & Winpenny, R. E. P. (2003). Angew. Chem. Int. Ed. 42, 5978-5981. [ISI] [CSD] [CrossRef] [ChemPort]
Lassahn, P.-G., Lozan, V., Timco, G. A., Christian, P., Janiak C. & Winpenny, R. E. P. (2004). J. Catal. 222, 260-267.
Meier, F., Levy, J. & Loss, D. (2003). Phys. Rev. Lett. 90, 047901-1. [CrossRef] [PubMed]
Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.
Sheldrick, G. M. (1997). SHELXL97 and SHELXS97. University of Göttingen, Germany.


Acta Cryst (2005). E61, m1525-m1527   [ doi:10.1107/S1600536805019562 ]