organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Salicylaldoxime-III at 150 K

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aSchool of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, Scotland, and bCambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England
*Correspondence e-mail: s.parsons@ed.ac.uk

(Received 13 August 2006; accepted 15 August 2006; online 18 August 2006)

Salicylaldoxime derivatives crystallize in either hydrogen-bonded ring or chain motifs. A polymorph of the parent compound, salicylaldoxime, characterized by ring formation, has been known for some time. We now report a new polymorph of salicylaldoxime (2-hydroxy­benzaldehyde oxime, C7H7NO2), which exhibits chain formation and which has two molecules per asymmetric unit. ππ stacking inter­actions occur between the chains. We refer to this polymorph as salicylaldoxime-III.

Comment

Salicylaldoximes bearing branched alkyl chains are used as extracta­nts to effect the separation and concentration operations in the hydro­metallurgical recovery of copper, accounting for around 30% of annual production (Kordosky, 2002[Kordosky, G. A. (2002). Proceedings of the International Solvent Extraction Conference, Cape Town, South Africa, 17-21 March 2002, pp. 853-862.]). The N2O22− donor set in bis-salicylaldoxime complexes is stabilized by inter­ligand hydrogen bonds, forming a pseudo­macrocyclic arrangement (e.g. Fig. 1[link]a). The high selectivity of salicylaldoximes for copper over other metal ions is the result of the compatibility of the size of the cavity at the centre of the pseudo-macrocycle and the ionic radius of Cu2+ (Smith et al., 2002[Smith, A. G., Tasker, P. A. & White, D. J. (2002). Coord. Chem. Rev. 241, 61-85.]).

[Scheme 1]

The crystal structure of the parent compound salicyl­aldoxime, (1), was determined using X-ray diffraction by Pfluger & Harlow (1973[Pfluger, C. E. & Harlow, R. L. (1973). Acta Cryst. B29, 2608-2609.]) [Cambridge Structural Database (CSD, Version 5.27; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]) refcode SALOXM]. We refer to the phase investigated by these workers as salicylaldoxime-I. We have recently shown that salicylaldoxime-I undergoes a phase transition at 5.3 GPa to a second phase, salicylaldoxime-II (Wood et al., 2006[Wood, P. A., Forgan, R. S., Henderson, D., Parsons, S., Pidcock, E., Tasker, P. A. & Warren, J. E. (2006). Acta Cryst. B. Accepted.]).

Salicylaldoxime-I crystallizes in space group P21/n. Pairs of mol­ecules, related by inversion centres, form inter­molecular O—H⋯O hydrogen bonds to produce a dimer (Fig. 1[link]b), for which the graph-set descriptor is R44(10) (Bernstein et al., 1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]). This dimeric form closely resembles the pseudo-macrocyclic arrangement observed in metal complexes, and is only observed in the free ligands in the solid state in salicyl­aldoxime derivatives which carry small substituents [e.g. CSD refcodes ABULIT (Xu et al., 2004[Xu, T., Li, L. & Ji, H. (2004). Hecheng Huaxue, 12, 22-24. (In Chinese.)]) and CLSALX (Simonsen et al., 1961[Simonsen, S. H., Pfluger, C. E. & Thompson, C. M. (1961). Acta Cryst. 14, 269-272.])]. Bulky alkyl substituents lead to hydrogen-bonded chain motifs in preference to rings [e.g. CSD refcodes HEPKET10 (Koziol & Kosturkiewicz, 1984[Koziol, A. E. & Kosturkiewicz, Z. (1984). Pol. J. Chem. 58, 569-75.]) and HELBOP (Maurin, 1994[Maurin, J. K. (1994). Acta Cryst. C50, 1357-1359.])].

We now report the crystal structure of a third polymorph of salicylaldoxime, salicylaldoxime-III, obtained under ambient conditions by recrystallization from a solution of hexane and chloro­form. Weissenberg photographs, taken using a crystal of salicylaldoxime obtained from alcohol, were indexed by Merritt & Schroeder (1956[Merritt, L. L. & Schroeder, E. (1956). Acta Cryst. 9, 194.]) on the basis of an ortho­rhom­bic cell with dimensions a = 12.69, b = 13.51 and c = 7.98 Å, although no coordinates were determined. These cell dimensions closely resemble those determined here for salicylaldoxime-III. In the same paper, the authors report a powder pattern, which Pfluger & Harlow (1973[Pfluger, C. E. & Harlow, R. L. (1973). Acta Cryst. B29, 2608-2609.]) claim actually corresponds to the monoclinic form, salicylaldoxime-I. However, a powder pattern simulated (using PLATON; Spek, 2006[Spek, A. L. (2006). PLATON. University of Utrecht, The Netherlands. PC version compiled by L. Farrugia, University of Glasgow, Scotland.]) on the basis of the structural parameters reported here for phase III more closely resembles the data reported by Merritt & Schroeder (1956[Merritt, L. L. & Schroeder, E. (1956). Acta Cryst. 9, 194.]) than the pattern calculated for phase I (sourcing coordinates from CSD refcode SALOXM). For example, the first six simulated d spacings for form III are 6.89, 6.36, 5.89, 5.74, 5.04 and 4.61 Å; the corresponding data for phase I are 9.59, 6.54, 6.26, 4.82, 4.71 and 4.50 Å, while the data reported by Merritt & Schroeder are 6.76, 6.32, 5.99, 5.68, 5.10 and 4.58 Å. We therefore disagree with Pfluger & Harlow's conclusion regarding the pattern reported by Merritt & Schroeder.

Salicylaldoxime-III is characterized by the formation of hydrogen-bonded chains rather than hydrogen-bonded rings. There are two mol­ecules in the asymmetric unit of salicyl­aldoxime-III (Fig. 2[link]), which alternate along a hydrogen-bonded chain formed by inter­molecular oximic O—H⋯O hydrogen bonds (Fig. 3[link]). The chains run along the crystallographic c axis, being generated by a ..21 operation. Intra­molecular phenolic O—H⋯N hydrogen bonds are also formed (Fig. 3[link]).

The chains inter­act with each other via ππ stacking contacts formed between two symmetry-independent mol­ecules. Within these stacking inter­actions, the atoms forming the phenyl ring of mol­ecule 2 (based on O12 etc.) lie between 3.394 (2) and 3.519 (2) Å from the mean plane of mol­ecule 1 (based on O11). The dihedral angle between the two phenyl planes is 2.69 (5)°.

[Figure 1]
Figure 1
Pseudomacrocycle formation by salicylaldoxime. (a) Salicylaldoxime complexation by copper(II). (b) Hydogen-bonded dimers formed in the crystal structure of salicylaldoxime-I. Dashed lines indicate hydrogen bonds.
[Figure 2]
Figure 2
The two mol­ecules comprising the asymmetric unit of salicylaldoxime-III. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as circles of arbitrary radii. Dashed lines indicate hydrogen bonds.
[Figure 3]
Figure 3
Hydrogen-bonded chains in salicylaldoxime-III. Dashed lines indicate hydrogen bonds.

Experimental

Salicylaldoxime was obtained from Acros. The solid was dissolved in chloro­form and enough hexane was added to induce precipitation of a small quality of solid. Chloro­form was added to redissolve the precipitated solid, and the solution was filtered into a small beaker through glass wool. Crystals of salicylaldoxime grew on allowing the solution to evaporate over the course of 5 d at room temperature.

Crystal data
  • C7H7NO2

  • Mr = 137.14

  • Orthorhombic, P 21 21 21

  • a = 7.6691 (2) Å

  • b = 12.7162 (3) Å

  • c = 13.3652 (3) Å

  • V = 1303.40 (5) Å3

  • Z = 8

  • Dx = 1.398 Mg m−3

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 150 K

  • Block, colourless

  • 0.42 × 0.25 × 0.18 mm

Data collection
  • Bruker SMART APEX CCD area-detector diffractometer

  • ω scans

  • Absorption correction: multi-scan (SADABS; Sheldrick, 2006[Sheldrick, G. M. (2006). SADABS. Version 2006/1. University of Göttingen, Germany.]) Tmin = 0.740, Tmax = 0.980

  • 15665 measured reflections

  • 1886 independent reflections

  • 1618 reflections with I > 2σ(I)

  • Rint = 0.061

  • θmax = 28.9°

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.033

  • wR(F2) = 0.079

  • S = 0.94

  • 1886 reflections

  • 194 parameters

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

  • w = 1/[σ2(F2) + (0.04P)2], where P = [max(Fo2,0) + 2Fc2]/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.22 e Å−3

  • Δρmin = −0.28 e Å−3

  • Extinction correction: Larson (1970[Larson, A. C. (1970). Crystallographic Computing, edited by F. R. Ahmed, S. R. Hall & C. P. Huber, pp. 291-294. Copenhagen: Munksgaard.]), equation 22

  • Extinction coefficient: 2.2 (2) × 102

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O11—H11⋯O52i 0.81 (2) 2.01 (2) 2.8137 (17) 176 (2)
O12—H12⋯O51ii 0.87 (2) 1.99 (2) 2.7945 (18) 155 (2)
O51—H51⋯N21 0.86 (2) 1.85 (2) 2.6384 (18) 152 (2)
O52—H52⋯N22 0.85 (2) 1.84 (2) 2.6285 (18) 153.4 (19)
Symmetry codes: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (ii) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1].

H atoms on O atoms (H11, H51, H12 and H52) were found in a difference Fourier map and their positions refined, subject to O—H distance restraints of 0.84 (5) Å and with Uiso(H) = 1.2Ueq(O). The remaining H atoms were positioned geometrically and constrained to ride on their host atoms, with C—H = 0.93–0.96 Å and with Uiso(H) = 1.2Ueq(C).

Data on this light-atom structure were collected with Mo Kα radiation, and dispersion effects are negligible. The absolute configuration of the crystal used for data collection has not been determined in this study. Friedel pairs were merged.

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART. Version 5.624. Bruker AXS, Madison, Wisconsin, USA.]); cell refinement: SAINT; data reduction: SAINT (Bruker, 2003[Bruker (2003). SAINT. Version 7. Bruker AXS, Madison, Wisconsin, USA.]); program(s) used to solve structure: SIR92 (Altomare et al., 1994[Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.]); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003[Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487.]); molecular graphics: DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Release 3.1d. Crystal Impact GbR, Bonn, Germany. https://www.crystalimpact.com/diamond]) and XP (Sheldrick, 1997[Sheldrick, G. M. (1997). XP. Version 5. University of Göttingen, Germany.]); software used to prepare material for publication: CRYSTALS and PLATON (Spek, 2006[Spek, A. L. (2006). PLATON. University of Utrecht, The Netherlands. PC version compiled by L. Farrugia, University of Glasgow, Scotland.]).

Supporting information


Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT; data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: DIAMOND (Brandenburg, 2006) and XP (Sheldrick, 1997); software used to prepare material for publication: CRYSTALS and PLATON (Spek, 2006).

2-hydroxybenzaldehyde oxime top
Crystal data top
C7H7NO2Dx = 1.398 Mg m3
Mr = 137.14Melting point = 332–334 K
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 7295 reflections
a = 7.6691 (2) Åθ = 2–28°
b = 12.7162 (3) ŵ = 0.10 mm1
c = 13.3652 (3) ÅT = 150 K
V = 1303.40 (5) Å3Block, colourless
Z = 80.42 × 0.25 × 0.18 mm
F(000) = 576
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
1618 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.061
ω scansθmax = 28.9°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2006)
h = 109
Tmin = 0.740, Tmax = 0.980k = 1716
15665 measured reflectionsl = 1717
1886 independent reflections
Refinement top
Refinement on F2Hydrogen site location: geom/difmap
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.033 w = 1/[σ2(F2) + (0.04P)2],
where P = [max(Fo2,0) + 2Fc2]/3
wR(F2) = 0.079(Δ/σ)max = 0.000152
S = 0.94Δρmax = 0.22 e Å3
1886 reflectionsΔρmin = 0.28 e Å3
194 parametersExtinction correction: Larson (1970), Equation 22
4 restraintsExtinction coefficient: 220 (20)
Primary atom site location: structure-invariant direct methods
Special details top

Experimental. Used Oxford Cryosystems low-temperature device.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O110.2811 (2)0.27564 (10)0.02463 (9)0.0368
N210.2508 (2)0.22621 (10)0.11662 (10)0.0274
C310.1828 (2)0.13549 (13)0.10589 (12)0.0264
C410.1437 (2)0.07010 (13)0.19232 (12)0.0242
C510.1779 (2)0.10191 (12)0.29136 (12)0.0238
O510.24867 (17)0.19816 (9)0.31221 (9)0.0286
C610.1421 (2)0.03505 (14)0.37079 (12)0.0291
C710.0716 (2)0.06313 (14)0.35366 (14)0.0322
C810.0356 (2)0.09565 (14)0.25657 (15)0.0313
C910.0725 (2)0.02997 (13)0.17736 (13)0.0285
O120.7865 (2)0.25663 (11)0.48433 (10)0.0407
N220.7161 (2)0.16559 (10)0.44076 (11)0.0286
C320.7209 (2)0.17066 (12)0.34528 (13)0.0275
C420.6555 (2)0.08496 (13)0.28352 (12)0.0246
C520.5891 (2)0.00828 (12)0.32393 (11)0.0243
O520.58579 (17)0.02492 (9)0.42557 (8)0.0308
C620.5244 (2)0.08673 (13)0.26243 (13)0.0286
C720.5285 (2)0.07423 (14)0.15954 (13)0.0303
C820.5959 (2)0.01694 (14)0.11784 (12)0.0298
C920.6577 (2)0.09598 (13)0.17902 (12)0.0275
H110.315 (3)0.3334 (17)0.0410 (18)0.0537*
H310.15800.10960.04270.0315*
H510.270 (3)0.2251 (17)0.2545 (15)0.0427*
H610.16670.05730.43650.0331*
H710.04820.10610.40910.0397*
H810.01410.16340.24580.0370*
H910.05440.05230.11010.0330*
H120.768 (3)0.2501 (18)0.5479 (17)0.0593*
H320.76540.23050.31300.0324*
H520.624 (3)0.0323 (16)0.4501 (15)0.0450*
H620.47610.14870.29230.0336*
H720.47910.12600.11800.0364*
H820.59490.02600.04720.0363*
H920.70260.15810.15080.0322*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O110.0607 (9)0.0291 (7)0.0207 (6)0.0041 (7)0.0001 (6)0.0029 (5)
N210.0348 (8)0.0267 (7)0.0206 (6)0.0048 (6)0.0006 (6)0.0018 (5)
C310.0299 (8)0.0279 (8)0.0213 (7)0.0046 (7)0.0029 (7)0.0036 (7)
C410.0215 (7)0.0248 (8)0.0264 (8)0.0037 (7)0.0003 (7)0.0010 (6)
C510.0237 (8)0.0222 (8)0.0253 (8)0.0036 (6)0.0011 (7)0.0017 (6)
O510.0410 (7)0.0236 (5)0.0213 (5)0.0023 (6)0.0000 (6)0.0016 (5)
C610.0332 (8)0.0293 (8)0.0246 (8)0.0022 (8)0.0040 (7)0.0017 (7)
C710.0338 (9)0.0281 (9)0.0348 (9)0.0023 (8)0.0098 (8)0.0033 (7)
C810.0283 (8)0.0250 (8)0.0408 (10)0.0019 (7)0.0048 (8)0.0048 (7)
C910.0263 (8)0.0281 (8)0.0310 (9)0.0010 (8)0.0024 (7)0.0070 (7)
O120.0677 (10)0.0285 (6)0.0259 (6)0.0054 (7)0.0019 (7)0.0051 (6)
N220.0384 (8)0.0223 (6)0.0252 (7)0.0037 (7)0.0003 (6)0.0021 (6)
C320.0339 (9)0.0233 (8)0.0254 (8)0.0024 (7)0.0024 (7)0.0018 (6)
C420.0243 (7)0.0263 (8)0.0231 (7)0.0057 (7)0.0017 (7)0.0012 (6)
C520.0250 (8)0.0276 (8)0.0204 (7)0.0056 (7)0.0023 (7)0.0005 (7)
O520.0442 (7)0.0275 (6)0.0208 (6)0.0037 (6)0.0028 (6)0.0023 (5)
C620.0287 (8)0.0271 (9)0.0300 (9)0.0009 (7)0.0016 (7)0.0003 (7)
C720.0290 (8)0.0327 (9)0.0292 (9)0.0051 (8)0.0049 (8)0.0069 (7)
C820.0314 (8)0.0392 (9)0.0187 (7)0.0085 (8)0.0003 (7)0.0018 (7)
C920.0305 (8)0.0290 (8)0.0229 (8)0.0043 (8)0.0021 (7)0.0030 (7)
Geometric parameters (Å, º) top
O11—N211.4003 (17)O12—N221.4039 (19)
O11—H110.81 (2)O12—H120.86 (2)
N21—C311.274 (2)N22—C321.278 (2)
C31—C411.454 (2)C32—C421.456 (2)
C31—H310.927C32—H320.939
C41—C511.409 (2)C42—C521.399 (2)
C41—C911.399 (2)C42—C921.404 (2)
C51—O511.3677 (19)C52—O521.3751 (19)
C51—C611.388 (2)C52—C621.385 (2)
O51—H510.86 (2)O52—H520.85 (2)
C61—C711.379 (3)C62—C721.385 (2)
C61—H610.942C62—H620.958
C71—C811.390 (3)C72—C821.386 (2)
C71—H710.938C72—H720.941
C81—C911.378 (2)C82—C921.380 (2)
C81—H810.953C82—H820.951
C91—H910.953C92—H920.940
N21—O11—H11102.9 (17)N22—O12—H12105.4 (16)
O11—N21—C31112.06 (13)O12—N22—C32111.20 (14)
N21—C31—C41120.83 (15)N22—C32—C42121.23 (16)
N21—C31—H31120.6N22—C32—H32120.7
C41—C31—H31118.6C42—C32—H32118.1
C31—C41—C51122.95 (14)C32—C42—C52122.73 (14)
C31—C41—C91119.13 (15)C32—C42—C92119.02 (15)
C51—C41—C91117.91 (15)C52—C42—C92118.24 (15)
C41—C51—O51121.49 (14)C42—C52—O52121.24 (14)
C41—C51—C61120.41 (15)C42—C52—C62120.80 (14)
O51—C51—C61118.10 (14)O52—C52—C62117.96 (15)
C51—O51—H51104.4 (14)C52—O52—H52104.1 (14)
C51—C61—C71120.34 (16)C52—C62—C72119.92 (16)
C51—C61—H61119.3C52—C62—H62118.9
C71—C61—H61120.4C72—C62—H62121.2
C61—C71—C81120.15 (17)C62—C72—C82120.24 (16)
C61—C71—H71118.1C62—C72—H72119.8
C81—C71—H71121.7C82—C72—H72119.9
C71—C81—C91119.74 (16)C72—C82—C92119.94 (15)
C71—C81—H81119.3C72—C82—H82119.8
C91—C81—H81120.9C92—C82—H82120.2
C41—C91—C81121.45 (16)C42—C92—C82120.85 (16)
C41—C91—H91117.5C42—C92—H92119.1
C81—C91—H91121.0C82—C92—H92120.0
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O11—H11···O52i0.81 (2)2.01 (2)2.8137 (17)176 (2)
O12—H12···O51ii0.87 (2)1.99 (2)2.7945 (18)155 (2)
O51—H51···N210.86 (2)1.85 (2)2.6384 (18)152 (2)
O52—H52···N220.85 (2)1.84 (2)2.6285 (18)153 (2)
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x+1/2, y+1/2, z+1.
 

Acknowledgements

The authors thank the EPSRC and the Cambridge Crystallographic Data Centre for funding.

References

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