organic compounds
Salicylaldoxime-III at 150 K
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
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 π–π 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). The N2O22− donor set in bis-salicylaldoxime complexes is stabilized by interligand hydrogen bonds, forming a pseudomacrocyclic arrangement (e.g. Fig. 1a). 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).
The ) [Cambridge Structural Database (CSD, Version 5.27; Allen, 2002) refcode SALOXM]. We refer to the phase investigated by these workers as salicylaldoxime-I. We have recently shown that salicylaldoxime-I undergoes a at 5.3 GPa to a second phase, salicylaldoxime-II (Wood et al., 2006).
of the parent compound salicylaldoxime, (1), was determined using X-ray diffraction by Pfluger & Harlow (1973Salicylaldoxime-I crystallizes in P21/n. Pairs of molecules, related by inversion centres, form intermolecular O—H⋯O hydrogen bonds to produce a dimer (Fig. 1b), for which the graph-set descriptor is R44(10) (Bernstein et al., 1995). 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) and CLSALX (Simonsen et al., 1961)]. Bulky alkyl substituents lead to hydrogen-bonded chain motifs in preference to rings [e.g. CSD refcodes HEPKET10 (Koziol & Kosturkiewicz, 1984) and HELBOP (Maurin, 1994)].
We now report the ) 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) claim actually corresponds to the monoclinic form, salicylaldoxime-I. However, a powder pattern simulated (using PLATON; Spek, 2006) on the basis of the structural parameters reported here for phase III more closely resembles the data reported by Merritt & Schroeder (1956) 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.
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 (1956Salicylaldoxime-III is characterized by the formation of hydrogen-bonded chains rather than hydrogen-bonded rings. There are two molecules in the ), which alternate along a hydrogen-bonded chain formed by intermolecular oximic O—H⋯O hydrogen bonds (Fig. 3). 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).
of salicylaldoxime-III (Fig. 2The chains interact with each other via π–π 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)°.
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
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Refinement
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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 of the crystal used for data collection has not been determined in this study. Friedel pairs were merged.
Data collection: SMART (Bruker, 2001); cell 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).
Supporting information
https://doi.org/10.1107/S1600536806032375/bt2170sup1.cif
contains datablocks global, 1. DOI:Structure factors: contains datablock 1. DOI: https://doi.org/10.1107/S1600536806032375/bt21701sup2.hkl
Data collection: SMART (Bruker, 2001); cell
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).C7H7NO2 | Dx = 1.398 Mg m−3 |
Mr = 137.14 | Melting point = 332–334 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 7295 reflections |
a = 7.6691 (2) Å | θ = 2–28° |
b = 12.7162 (3) Å | µ = 0.10 mm−1 |
c = 13.3652 (3) Å | T = 150 K |
V = 1303.40 (5) Å3 | Block, colourless |
Z = 8 | 0.42 × 0.25 × 0.18 mm |
F(000) = 576 |
Bruker SMART APEX CCD area-detector diffractometer | 1618 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.061 |
ω scans | θmax = 28.9°, θmin = 2.2° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | h = −10→9 |
Tmin = 0.740, Tmax = 0.980 | k = −17→16 |
15665 measured reflections | l = −17→17 |
1886 independent reflections |
Refinement on F2 | Hydrogen site location: geom/difmap |
Least-squares matrix: full | H 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 = 0.94 | Δρmax = 0.22 e Å−3 |
1886 reflections | Δρmin = −0.28 e Å−3 |
194 parameters | Extinction correction: Larson (1970), Equation 22 |
4 restraints | Extinction coefficient: 220 (20) |
Primary atom site location: structure-invariant direct methods |
x | y | z | Uiso*/Ueq | ||
O11 | 0.2811 (2) | 0.27564 (10) | 0.02463 (9) | 0.0368 | |
N21 | 0.2508 (2) | 0.22621 (10) | 0.11662 (10) | 0.0274 | |
C31 | 0.1828 (2) | 0.13549 (13) | 0.10589 (12) | 0.0264 | |
C41 | 0.1437 (2) | 0.07010 (13) | 0.19232 (12) | 0.0242 | |
C51 | 0.1779 (2) | 0.10191 (12) | 0.29136 (12) | 0.0238 | |
O51 | 0.24867 (17) | 0.19816 (9) | 0.31221 (9) | 0.0286 | |
C61 | 0.1421 (2) | 0.03505 (14) | 0.37079 (12) | 0.0291 | |
C71 | 0.0716 (2) | −0.06313 (14) | 0.35366 (14) | 0.0322 | |
C81 | 0.0356 (2) | −0.09565 (14) | 0.25657 (15) | 0.0313 | |
C91 | 0.0725 (2) | −0.02997 (13) | 0.17736 (13) | 0.0285 | |
O12 | 0.7865 (2) | 0.25663 (11) | 0.48433 (10) | 0.0407 | |
N22 | 0.7161 (2) | 0.16559 (10) | 0.44076 (11) | 0.0286 | |
C32 | 0.7209 (2) | 0.17066 (12) | 0.34528 (13) | 0.0275 | |
C42 | 0.6555 (2) | 0.08496 (13) | 0.28352 (12) | 0.0246 | |
C52 | 0.5891 (2) | −0.00828 (12) | 0.32393 (11) | 0.0243 | |
O52 | 0.58579 (17) | −0.02492 (9) | 0.42557 (8) | 0.0308 | |
C62 | 0.5244 (2) | −0.08673 (13) | 0.26243 (13) | 0.0286 | |
C72 | 0.5285 (2) | −0.07423 (14) | 0.15954 (13) | 0.0303 | |
C82 | 0.5959 (2) | 0.01694 (14) | 0.11784 (12) | 0.0298 | |
C92 | 0.6577 (2) | 0.09598 (13) | 0.17902 (12) | 0.0275 | |
H11 | 0.315 (3) | 0.3334 (17) | 0.0410 (18) | 0.0537* | |
H31 | 0.1580 | 0.1096 | 0.0427 | 0.0315* | |
H51 | 0.270 (3) | 0.2251 (17) | 0.2545 (15) | 0.0427* | |
H61 | 0.1667 | 0.0573 | 0.4365 | 0.0331* | |
H71 | 0.0482 | −0.1061 | 0.4091 | 0.0397* | |
H81 | −0.0141 | −0.1634 | 0.2458 | 0.0370* | |
H91 | 0.0544 | −0.0523 | 0.1101 | 0.0330* | |
H12 | 0.768 (3) | 0.2501 (18) | 0.5479 (17) | 0.0593* | |
H32 | 0.7654 | 0.2305 | 0.3130 | 0.0324* | |
H52 | 0.624 (3) | 0.0323 (16) | 0.4501 (15) | 0.0450* | |
H62 | 0.4761 | −0.1487 | 0.2923 | 0.0336* | |
H72 | 0.4791 | −0.1260 | 0.1180 | 0.0364* | |
H82 | 0.5949 | 0.0260 | 0.0472 | 0.0363* | |
H92 | 0.7026 | 0.1581 | 0.1508 | 0.0322* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O11 | 0.0607 (9) | 0.0291 (7) | 0.0207 (6) | −0.0041 (7) | 0.0001 (6) | 0.0029 (5) |
N21 | 0.0348 (8) | 0.0267 (7) | 0.0206 (6) | 0.0048 (6) | −0.0006 (6) | 0.0018 (5) |
C31 | 0.0299 (8) | 0.0279 (8) | 0.0213 (7) | 0.0046 (7) | −0.0029 (7) | −0.0036 (7) |
C41 | 0.0215 (7) | 0.0248 (8) | 0.0264 (8) | 0.0037 (7) | −0.0003 (7) | −0.0010 (6) |
C51 | 0.0237 (8) | 0.0222 (8) | 0.0253 (8) | 0.0036 (6) | 0.0011 (7) | −0.0017 (6) |
O51 | 0.0410 (7) | 0.0236 (5) | 0.0213 (5) | −0.0023 (6) | 0.0000 (6) | −0.0016 (5) |
C61 | 0.0332 (8) | 0.0293 (8) | 0.0246 (8) | 0.0022 (8) | 0.0040 (7) | −0.0017 (7) |
C71 | 0.0338 (9) | 0.0281 (9) | 0.0348 (9) | 0.0023 (8) | 0.0098 (8) | 0.0033 (7) |
C81 | 0.0283 (8) | 0.0250 (8) | 0.0408 (10) | −0.0019 (7) | 0.0048 (8) | −0.0048 (7) |
C91 | 0.0263 (8) | 0.0281 (8) | 0.0310 (9) | 0.0010 (8) | −0.0024 (7) | −0.0070 (7) |
O12 | 0.0677 (10) | 0.0285 (6) | 0.0259 (6) | −0.0054 (7) | −0.0019 (7) | −0.0051 (6) |
N22 | 0.0384 (8) | 0.0223 (6) | 0.0252 (7) | 0.0037 (7) | −0.0003 (6) | −0.0021 (6) |
C32 | 0.0339 (9) | 0.0233 (8) | 0.0254 (8) | 0.0024 (7) | 0.0024 (7) | 0.0018 (6) |
C42 | 0.0243 (7) | 0.0263 (8) | 0.0231 (7) | 0.0057 (7) | 0.0017 (7) | −0.0012 (6) |
C52 | 0.0250 (8) | 0.0276 (8) | 0.0204 (7) | 0.0056 (7) | 0.0023 (7) | 0.0005 (7) |
O52 | 0.0442 (7) | 0.0275 (6) | 0.0208 (6) | −0.0037 (6) | 0.0028 (6) | 0.0023 (5) |
C62 | 0.0287 (8) | 0.0271 (9) | 0.0300 (9) | 0.0009 (7) | −0.0016 (7) | 0.0003 (7) |
C72 | 0.0290 (8) | 0.0327 (9) | 0.0292 (9) | 0.0051 (8) | −0.0049 (8) | −0.0069 (7) |
C82 | 0.0314 (8) | 0.0392 (9) | 0.0187 (7) | 0.0085 (8) | −0.0003 (7) | −0.0018 (7) |
C92 | 0.0305 (8) | 0.0290 (8) | 0.0229 (8) | 0.0043 (8) | 0.0021 (7) | 0.0030 (7) |
O11—N21 | 1.4003 (17) | O12—N22 | 1.4039 (19) |
O11—H11 | 0.81 (2) | O12—H12 | 0.86 (2) |
N21—C31 | 1.274 (2) | N22—C32 | 1.278 (2) |
C31—C41 | 1.454 (2) | C32—C42 | 1.456 (2) |
C31—H31 | 0.927 | C32—H32 | 0.939 |
C41—C51 | 1.409 (2) | C42—C52 | 1.399 (2) |
C41—C91 | 1.399 (2) | C42—C92 | 1.404 (2) |
C51—O51 | 1.3677 (19) | C52—O52 | 1.3751 (19) |
C51—C61 | 1.388 (2) | C52—C62 | 1.385 (2) |
O51—H51 | 0.86 (2) | O52—H52 | 0.85 (2) |
C61—C71 | 1.379 (3) | C62—C72 | 1.385 (2) |
C61—H61 | 0.942 | C62—H62 | 0.958 |
C71—C81 | 1.390 (3) | C72—C82 | 1.386 (2) |
C71—H71 | 0.938 | C72—H72 | 0.941 |
C81—C91 | 1.378 (2) | C82—C92 | 1.380 (2) |
C81—H81 | 0.953 | C82—H82 | 0.951 |
C91—H91 | 0.953 | C92—H92 | 0.940 |
N21—O11—H11 | 102.9 (17) | N22—O12—H12 | 105.4 (16) |
O11—N21—C31 | 112.06 (13) | O12—N22—C32 | 111.20 (14) |
N21—C31—C41 | 120.83 (15) | N22—C32—C42 | 121.23 (16) |
N21—C31—H31 | 120.6 | N22—C32—H32 | 120.7 |
C41—C31—H31 | 118.6 | C42—C32—H32 | 118.1 |
C31—C41—C51 | 122.95 (14) | C32—C42—C52 | 122.73 (14) |
C31—C41—C91 | 119.13 (15) | C32—C42—C92 | 119.02 (15) |
C51—C41—C91 | 117.91 (15) | C52—C42—C92 | 118.24 (15) |
C41—C51—O51 | 121.49 (14) | C42—C52—O52 | 121.24 (14) |
C41—C51—C61 | 120.41 (15) | C42—C52—C62 | 120.80 (14) |
O51—C51—C61 | 118.10 (14) | O52—C52—C62 | 117.96 (15) |
C51—O51—H51 | 104.4 (14) | C52—O52—H52 | 104.1 (14) |
C51—C61—C71 | 120.34 (16) | C52—C62—C72 | 119.92 (16) |
C51—C61—H61 | 119.3 | C52—C62—H62 | 118.9 |
C71—C61—H61 | 120.4 | C72—C62—H62 | 121.2 |
C61—C71—C81 | 120.15 (17) | C62—C72—C82 | 120.24 (16) |
C61—C71—H71 | 118.1 | C62—C72—H72 | 119.8 |
C81—C71—H71 | 121.7 | C82—C72—H72 | 119.9 |
C71—C81—C91 | 119.74 (16) | C72—C82—C92 | 119.94 (15) |
C71—C81—H81 | 119.3 | C72—C82—H82 | 119.8 |
C91—C81—H81 | 120.9 | C92—C82—H82 | 120.2 |
C41—C91—C81 | 121.45 (16) | C42—C92—C82 | 120.85 (16) |
C41—C91—H91 | 117.5 | C42—C92—H92 | 119.1 |
C81—C91—H91 | 121.0 | C82—C92—H92 | 120.0 |
D—H···A | D—H | H···A | D···A | 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 (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.
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