research communications
H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocine
of 4,10-dimethoxy-13-methyl-6aDepartment of Chemistry, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, Kyiv 01601, Ukraine, and bSchool of Molecular Sciences, M310, University of Western Australia, Perth, WA 6009, Australia
*Correspondence e-mail: vassilyeva@univ.kiev.ua
The title compound, C17H17NO4, lacks with one molecule per The molecule exists in a folded butterfly-like conformation; the benzene rings form a dihedral angle of 84.72 (7)°. The central eight-membered imino-bridged dioxocin ring adopts a twisted-boat conformation. In the crystal, inversion-related molecules are linked by pairs of weak C—H⋯O hydrogen bonds, forming double-stranded chains parallel to the a axis.
Keywords: crystal structure; o-vanillin; methylamine hydrochloride; Schiff base; self-condensation; [1,5]dioxocin ring; twisted-boat conformation.
CCDC reference: 1532218
1. Chemical context
Tröger's base and its structural analogues are characterized by two flat, usually aromatic and identical, pincers interlocked in an almost perpendicular fashion (Dolenský et al., 2012). Both the and the conformational rigidity of their central diazocine, dioxocin or dithiocin skeletons are the reasons why these cleft-shaped molecules have been of interest in molecular recognition (Hardouin-Lerouge et al., 2011), as chiral solvating agents (Wilen et al., 1991), and in the field of (Minder et al., 1995).
Over the last few years, we have been exploring the chemistry of transition metal complexes of Schiff base ligands with the aim of preparing heterometallic polynuclear compounds with diverse potential advantages (Chygorin et al., 2012; Nesterova et al., 2013). The Schiff base ligand 2-methoxy-6-iminomethylphenol (HL) with various connectivity modes has been successfully used as a multidentate linker between several metal centres by our group and others (Meally et al., 2010; Sydoruk et al., 2013). The HL ligand is usually obtained by the standard method of condensation of the substituted salicylaldehyde with an aqueous solution of methylamine in methanol (Meally et al., 2010). In the present work, we used a mixture of 2-hydroxy-3-methoxy-benzaldehyde and methylamine hydrochloride to react with a zinc salt in an attempt to synthesize a Zn complex with the HL ligand (see Scheme). The resulting Schiff base apparently underwent self-condensation to form the substituted dibenzoimino[1,5]dioxocin, 4,10-dimethoxy-13-methyl-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocine, (I), the of which is presented here. A close analogue of the title compound was reported to result from 2-(N-methyliminomethyl)phenol, a liquid product of a similar condensation of salicylaldehyde and methylamine, after a few months storage in mild conditions (Filarowski et al., 1998). A tentative mechanism for the formation of the [1,5]iminodioxocin ring in the reaction between an aromatic aldehyde and a primary amine was given by Mandal et al. (2006).
2. Structural commentary
The title compound is composed of four fused rings including two benzene (C11–C16 and C21–C26) and two six-membered heterocyclic rings (O11/C11/C12/C121/N1/C221 and O21/C21/C22/C221/N1/C121) (Fig. 1). The organic molecule has two chiral centres and lacks the crystal is racemic. The molecule exists in a folded butterfly-like conformation with a dihedral (folding) angle between the two benzene rings of 84.72 (7)°. The eight-membered imino-bridged dioxocin ring adopts a twisted-boat conformation, as judged from the eight torsion angles observed within this ring (τ1–τ8) (Mandal et al., 2006). The bond lengths and angles are unexceptional and are closely related to those of N-methyl-2,6,-dioxa-9-aza-(c,g)dibenzo(3.3.1)nonane (CSD refcode UCERIE; Filarowski et al., 1998); the dihedral angle of 84.72 (7)° is larger than that in the unsubstituted iminodioxocin molecule (80.95°).
3. Supramolecular features
In the crystal, double-stranded chains of inversion-related molecules linked by pairs of weak C–H⋯O hydrogen bonds (Table 1) propagate in the a-axis direction (Fig. 2). Adjacent hydrogen-bonded chains are arranged in a parallel fashion to ensure efficient crystal packing of the clefts. Surprisingly, neither π–π stacking [the shortest centroid–centroid distance (offset) = 3.96 Å] nor C—H⋯π interactions (the shortest H⋯centroid distance = 3.34 Å) play a significant role in formation of the of (I).
4. Database survey
More than 1000 crystal structures of molecules featuring eight-membered heterocine rings with two oxygen atoms in a 1,2-, 1,3-, 1,4- and 1,5-relationship, both uncondensed and fused to five-, six-, and seven-membered carbocycles or heterocycles, are found in the Cambridge Structural Database (CSD Version 5.37 plus one update; Groom et al., 2016) with bridged dioxocines constituting the majority of the compounds reported. Of theses, only five molecules contain the same central imino-bridged [1,5]dioxocin core as in compound (I) (refcodes GAQNUJ, QAYTIU, TECMAP, UCERIE, XESBON). Clearly, substituents on the aromatic rings and on the bridging imino N atom in the five compounds determine the differences in their folding angles, which fall in the range 78.49–96.84°. However, no obvious correlation between the nature/size/position of the substituents and widening of the folding angle can be established due to the small number of compounds involved. While an example of [1,5]iminodioxocin bridgehead N-atom coordination to a metal atom (copper) has been reported (refcode XESBON; Mandal et al., 2006), the Zn atom did not demonstrate the ability to coordinate the ligand (I) in the present study.
5. Synthesis and crystallization
2-Hydroxy-3-methoxy-benzaldehyde (0.23 g, 1.5 mmol) and methylamine hydrochloride (0.10 g, 1.5 mmol) were added to methanol (5 ml) and stirred magnetically for 10 min. Zn(CH3COO)2·2H2O (0.11 g, 0.5 mmol) dissolved in 5 ml dimethylformamide was added to the yellow solution of the Schiff base formed in situ, and the resulting deep-yellow solution was stirred at room temperature for an hour. The addition of N(Et)3 (1 ml) produced a light precipitate which was filtered off. The solution, which was kept cold (283–285 K), changed colour from yellow to brown. It was diluted twice with methanol (4 ml) since it was thickening. Brown plate-like crystals of the title compound formed over two months after successive addition of PriOH (4 ml) in two portions. They were collected by filter-suction, washed with dry PriOH and finally dried in air (yield: 23%). Analysis calculated for C17H17NO4 (299.31): C, 68.21; H, 5.72; N, 4.68%. Found: C, 68.55; H, 5.49; N, 4.87%. 1H NMR (400 MHz, DMSO-d6, s, singlet; m, multiplet): δ (ppm) 6.89–6.79, m (6H, benzene rings); 5.69, s (2H, dioxocin ring); 3.71, s (6H, OCH3); 2.51, s (3H, NCH3). The IR spectrum of powdered (I) in the range 4000–400 cm−1 shows all characteristic functional groups peaks: ν(CH) due to aromatic =C—H and alkyl –C—H stretching above and below 3000, respectively, the aromatic rings vibrations in the 1600–1400 region, ν(CO) and ν(CN) at 1300–1000 and aromatic CH bending in the 900–600 cm−1 region (see Supporting information).
6. Refinement
Crystal data, data collection and structure . All hydrogen atoms bound to carbon were included in calculated positions and refined using a riding model with isotropic displacement parameters based on those of the parent atom (C—H = 0.95 Å, Uiso(H) = 1.2UeqC for CH, C—H = 0.98 Å, Uiso(H) = 1.5UeqC for CH3). Anisotropic displacement parameters were employed for the non-hydrogen atoms.
details are summarized in Table 2Supporting information
CCDC reference: 1532218
https://doi.org/10.1107/S2056989017002328/hg5482sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017002328/hg5482Isup2.hkl
IR spectrum in KBr. DOI: https://doi.org/10.1107/S2056989017002328/hg5482sup3.pdf
Supporting information file. DOI: https://doi.org/10.1107/S2056989017002328/hg5482Isup4.cml
Data collection: CrysAlis PRO (Rigaku OD, 2015); cell
CrysAlis PRO (Rigaku OD, 2015); data reduction: CrysAlis PRO (Rigaku OD, 2015); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg, 1999) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).C17H17NO4 | Z = 2 |
Mr = 299.31 | F(000) = 316 |
Triclinic, P1 | Dx = 1.429 Mg m−3 |
Hall symbol: -P 1 | Cu Kα radiation, λ = 1.54184 Å |
a = 6.9956 (5) Å | Cell parameters from 2735 reflections |
b = 8.8589 (6) Å | θ = 3.9–67.1° |
c = 12.0938 (9) Å | µ = 0.84 mm−1 |
α = 93.980 (6)° | T = 100 K |
β = 106.603 (7)° | Plate, brown |
γ = 102.133 (6)° | 0.18 × 0.06 × 0.04 mm |
V = 695.46 (9) Å3 |
Oxford Diffraction Gemini diffractometer | 2456 independent reflections |
Radiation source: sealed X-ray tube | 2147 reflections with I > 2σ(I) |
Mirror monochromator | Rint = 0.027 |
Detector resolution: 10.4738 pixels mm-1 | θmax = 67.2°, θmin = 3.9° |
ω scans | h = −8→8 |
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2015) | k = −9→10 |
Tmin = 0.818, Tmax = 1 | l = −12→14 |
5235 measured reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.041 | H-atom parameters constrained |
wR(F2) = 0.121 | w = 1/[σ2(Fo2) + (0.0737P)2 + 0.1321P] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max < 0.001 |
2456 reflections | Δρmax = 0.22 e Å−3 |
202 parameters | Δρmin = −0.25 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.8680 (3) | 0.77719 (18) | 0.96792 (13) | 0.0272 (4) | |
H1A | 1.0173 | 0.8034 | 1.0043 | 0.041* | |
H1B | 0.802 | 0.8059 | 1.0249 | 0.041* | |
H1C | 0.8334 | 0.8345 | 0.9014 | 0.041* | |
N1 | 0.7947 (2) | 0.60859 (15) | 0.92762 (11) | 0.0239 (3) | |
C11 | 0.6973 (2) | 0.64283 (16) | 0.69544 (13) | 0.0208 (3) | |
O11 | 0.89314 (15) | 0.63442 (12) | 0.75392 (9) | 0.0216 (3) | |
C12 | 0.5341 (2) | 0.60187 (17) | 0.74052 (13) | 0.0220 (3) | |
C121 | 0.5761 (2) | 0.56411 (17) | 0.86455 (13) | 0.0234 (3) | |
H121 | 0.5042 | 0.624 | 0.9056 | 0.028* | |
C13 | 0.3363 (2) | 0.60620 (17) | 0.67238 (14) | 0.0248 (3) | |
H13 | 0.2232 | 0.5779 | 0.7016 | 0.03* | |
C14 | 0.3059 (2) | 0.65148 (18) | 0.56296 (14) | 0.0260 (4) | |
H14 | 0.1707 | 0.6494 | 0.5159 | 0.031* | |
C15 | 0.4714 (2) | 0.70032 (17) | 0.52068 (13) | 0.0245 (3) | |
H15 | 0.4492 | 0.7351 | 0.4465 | 0.029* | |
C16 | 0.6678 (2) | 0.69812 (17) | 0.58676 (13) | 0.0217 (3) | |
O16 | 0.84270 (16) | 0.74649 (12) | 0.55663 (9) | 0.0252 (3) | |
C161 | 0.8176 (3) | 0.80636 (19) | 0.44818 (13) | 0.0280 (4) | |
H16A | 0.7297 | 0.7244 | 0.3846 | 0.042* | |
H16B | 0.9522 | 0.8411 | 0.4367 | 0.042* | |
H16C | 0.7536 | 0.8946 | 0.4488 | 0.042* | |
C21 | 0.6140 (2) | 0.31265 (18) | 0.82770 (12) | 0.0214 (3) | |
O21 | 0.50055 (16) | 0.40035 (12) | 0.86700 (9) | 0.0242 (3) | |
C22 | 0.8031 (2) | 0.37774 (17) | 0.81425 (12) | 0.0215 (3) | |
C221 | 0.8989 (2) | 0.55005 (17) | 0.85422 (13) | 0.0218 (3) | |
H221 | 1.0459 | 0.563 | 0.9011 | 0.026* | |
C23 | 0.9039 (2) | 0.28166 (18) | 0.76738 (13) | 0.0232 (3) | |
H23 | 1.033 | 0.3251 | 0.7573 | 0.028* | |
C24 | 0.8164 (2) | 0.12416 (18) | 0.73579 (13) | 0.0241 (3) | |
H24 | 0.8838 | 0.0603 | 0.7017 | 0.029* | |
C25 | 0.6289 (2) | 0.05727 (18) | 0.75355 (13) | 0.0235 (3) | |
H25 | 0.5711 | −0.0517 | 0.7332 | 0.028* | |
C26 | 0.5290 (2) | 0.15091 (18) | 0.80075 (13) | 0.0225 (3) | |
O26 | 0.34536 (17) | 0.10158 (12) | 0.82185 (10) | 0.0275 (3) | |
C261 | 0.2625 (3) | −0.06296 (19) | 0.80651 (16) | 0.0326 (4) | |
H26A | 0.2318 | −0.1056 | 0.7247 | 0.049* | |
H26B | 0.1359 | −0.0843 | 0.8284 | 0.049* | |
H26C | 0.3628 | −0.1118 | 0.8559 | 0.049* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0350 (9) | 0.0211 (8) | 0.0248 (8) | 0.0057 (7) | 0.0094 (7) | 0.0021 (6) |
N1 | 0.0294 (7) | 0.0195 (7) | 0.0237 (6) | 0.0051 (5) | 0.0100 (5) | 0.0035 (5) |
C11 | 0.0217 (7) | 0.0147 (7) | 0.0253 (7) | 0.0047 (6) | 0.0061 (6) | 0.0013 (5) |
O11 | 0.0214 (5) | 0.0201 (5) | 0.0240 (6) | 0.0041 (4) | 0.0077 (4) | 0.0064 (4) |
C12 | 0.0261 (8) | 0.0138 (7) | 0.0270 (8) | 0.0045 (6) | 0.0103 (6) | 0.0020 (5) |
C121 | 0.0282 (8) | 0.0166 (7) | 0.0290 (8) | 0.0064 (6) | 0.0134 (6) | 0.0044 (6) |
C13 | 0.0236 (8) | 0.0165 (7) | 0.0362 (8) | 0.0042 (6) | 0.0129 (6) | 0.0023 (6) |
C14 | 0.0239 (8) | 0.0197 (8) | 0.0331 (8) | 0.0070 (6) | 0.0057 (6) | 0.0027 (6) |
C15 | 0.0294 (8) | 0.0199 (8) | 0.0242 (7) | 0.0073 (6) | 0.0070 (6) | 0.0043 (6) |
C16 | 0.0250 (7) | 0.0158 (7) | 0.0253 (7) | 0.0043 (6) | 0.0099 (6) | 0.0017 (6) |
O16 | 0.0257 (6) | 0.0272 (6) | 0.0250 (6) | 0.0060 (4) | 0.0108 (4) | 0.0084 (4) |
C161 | 0.0327 (8) | 0.0287 (9) | 0.0257 (8) | 0.0077 (7) | 0.0125 (7) | 0.0091 (6) |
C21 | 0.0246 (7) | 0.0202 (8) | 0.0222 (7) | 0.0080 (6) | 0.0094 (6) | 0.0046 (6) |
O21 | 0.0282 (6) | 0.0167 (6) | 0.0330 (6) | 0.0060 (4) | 0.0169 (5) | 0.0052 (4) |
C22 | 0.0240 (7) | 0.0201 (8) | 0.0203 (7) | 0.0054 (6) | 0.0060 (6) | 0.0063 (6) |
C221 | 0.0239 (7) | 0.0205 (8) | 0.0218 (7) | 0.0048 (6) | 0.0075 (6) | 0.0072 (6) |
C23 | 0.0221 (7) | 0.0261 (8) | 0.0240 (7) | 0.0073 (6) | 0.0092 (6) | 0.0075 (6) |
C24 | 0.0281 (8) | 0.0236 (8) | 0.0251 (7) | 0.0125 (6) | 0.0101 (6) | 0.0052 (6) |
C25 | 0.0280 (8) | 0.0176 (8) | 0.0258 (7) | 0.0063 (6) | 0.0089 (6) | 0.0046 (6) |
C26 | 0.0227 (7) | 0.0218 (8) | 0.0249 (7) | 0.0060 (6) | 0.0091 (6) | 0.0065 (6) |
O26 | 0.0277 (6) | 0.0177 (6) | 0.0415 (6) | 0.0035 (4) | 0.0183 (5) | 0.0060 (4) |
C261 | 0.0319 (9) | 0.0183 (8) | 0.0505 (10) | 0.0024 (7) | 0.0196 (8) | 0.0064 (7) |
C1—N1 | 1.4716 (19) | O16—C161 | 1.4271 (18) |
C1—H1A | 0.98 | C161—H16A | 0.98 |
C1—H1B | 0.98 | C161—H16B | 0.98 |
C1—H1C | 0.98 | C161—H16C | 0.98 |
N1—C221 | 1.433 (2) | C21—O21 | 1.3723 (18) |
N1—C121 | 1.454 (2) | C21—C22 | 1.387 (2) |
C11—O11 | 1.3707 (18) | C21—C26 | 1.407 (2) |
C11—C12 | 1.394 (2) | C22—C23 | 1.399 (2) |
C11—C16 | 1.410 (2) | C22—C221 | 1.515 (2) |
O11—C221 | 1.4636 (17) | C221—H221 | 1 |
C12—C13 | 1.403 (2) | C23—C24 | 1.379 (2) |
C12—C121 | 1.519 (2) | C23—H23 | 0.95 |
C121—O21 | 1.4413 (18) | C24—C25 | 1.403 (2) |
C121—H121 | 1 | C24—H24 | 0.95 |
C13—C14 | 1.381 (2) | C25—C26 | 1.381 (2) |
C13—H13 | 0.95 | C25—H25 | 0.95 |
C14—C15 | 1.395 (2) | C26—O26 | 1.3690 (19) |
C14—H14 | 0.95 | O26—C261 | 1.4286 (18) |
C15—C16 | 1.382 (2) | C261—H26A | 0.98 |
C15—H15 | 0.95 | C261—H26B | 0.98 |
C16—O16 | 1.3675 (19) | C261—H26C | 0.98 |
N1—C1—H1A | 109.5 | H16A—C161—H16B | 109.5 |
N1—C1—H1B | 109.5 | O16—C161—H16C | 109.5 |
H1A—C1—H1B | 109.5 | H16A—C161—H16C | 109.5 |
N1—C1—H1C | 109.5 | H16B—C161—H16C | 109.5 |
H1A—C1—H1C | 109.5 | O21—C21—C22 | 122.61 (14) |
H1B—C1—H1C | 109.5 | O21—C21—C26 | 116.68 (13) |
C221—N1—C121 | 107.32 (12) | C22—C21—C26 | 120.72 (14) |
C221—N1—C1 | 114.33 (12) | C21—O21—C121 | 111.48 (11) |
C121—N1—C1 | 112.09 (12) | C21—C22—C23 | 119.15 (14) |
O11—C11—C12 | 122.53 (13) | C21—C22—C221 | 119.33 (13) |
O11—C11—C16 | 116.70 (13) | C23—C22—C221 | 121.48 (13) |
C12—C11—C16 | 120.76 (13) | N1—C221—O11 | 111.99 (12) |
C11—O11—C221 | 111.80 (11) | N1—C221—C22 | 109.13 (12) |
C11—C12—C13 | 118.88 (14) | O11—C221—C22 | 110.50 (11) |
C11—C12—C121 | 119.41 (13) | N1—C221—H221 | 108.4 |
C13—C12—C121 | 121.58 (13) | O11—C221—H221 | 108.4 |
O21—C121—N1 | 108.62 (12) | C22—C221—H221 | 108.4 |
O21—C121—C12 | 111.51 (12) | C24—C23—C22 | 120.23 (14) |
N1—C121—C12 | 111.31 (12) | C24—C23—H23 | 119.9 |
O21—C121—H121 | 108.4 | C22—C23—H23 | 119.9 |
N1—C121—H121 | 108.4 | C23—C24—C25 | 120.62 (14) |
C12—C121—H121 | 108.4 | C23—C24—H24 | 119.7 |
C14—C13—C12 | 120.10 (14) | C25—C24—H24 | 119.7 |
C14—C13—H13 | 120 | C26—C25—C24 | 119.59 (14) |
C12—C13—H13 | 120 | C26—C25—H25 | 120.2 |
C13—C14—C15 | 120.80 (14) | C24—C25—H25 | 120.2 |
C13—C14—H14 | 119.6 | O26—C26—C25 | 125.72 (14) |
C15—C14—H14 | 119.6 | O26—C26—C21 | 114.69 (13) |
C16—C15—C14 | 119.99 (14) | C25—C26—C21 | 119.56 (14) |
C16—C15—H15 | 120 | C26—O26—C261 | 116.82 (12) |
C14—C15—H15 | 120 | O26—C261—H26A | 109.5 |
O16—C16—C15 | 125.65 (14) | O26—C261—H26B | 109.5 |
O16—C16—C11 | 115.10 (13) | H26A—C261—H26B | 109.5 |
C15—C16—C11 | 119.24 (14) | O26—C261—H26C | 109.5 |
C16—O16—C161 | 116.22 (11) | H26A—C261—H26C | 109.5 |
O16—C161—H16A | 109.5 | H26B—C261—H26C | 109.5 |
O16—C161—H16B | 109.5 |
D—H···A | D—H | H···A | D···A | D—H···A |
C13—H13···O11i | 0.95 | 2.69 | 3.5616 (19) | 152 |
C1—H1B···O26ii | 0.98 | 2.53 | 3.508 (2) | 176 |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y+1, −z+2. |
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