The Missing Link Crystallized from the Ionic Liquid 1-Ethyl-3-methylimidazolium Tosylate: Bis-aqua-(p-toluenesulfonato-O)-europium(III)-bis-p-toluenesulfonate Dihydrate
CRYSTAL GROWTH & DESIGN 2009 VOL. 9, NO. 6 2549–2551
Si-Fu Tang and Anja-Verena Mudring* Anorganische Chemie I - Festko¨rperchemie und Materialien, Ruhr-UniVersita¨t Bochum, 44801, Bochum, Germany ReceiVed January 10, 2009; ReVised Manuscript ReceiVed April 14, 2009
ABSTRACT: Bis-aqua-(p-toluenesulfonato-O)-europium(III)-bis-p-toluenesulfonate-dihydrate (1) was synthesized and structurally characterized. The crystal structure contains eight-coordinate europium(III) atoms. One oxygen atom from p-toluenesulfonate and seven aqua ligands form a slightly distorted square antiprism around Eu(III). A variety of O-H · · · O and intermolecular C-H · · · O hydrogen bonds link the asymmetric units into a two-dimensional layer, and these layers are further assembled into a three-dimensional supramolecular structure through intermolecular C-H · · · O hydrogen bonds and edge-to-face C-H · · · π interactions. The compound represents the structural missing link between the well-known lanthanide (Ln) tosylate (Tos) hydrates [(Ln(H2O)9](p-Tos)3(H2O) with noncoordinating tosylate and [Ln(H2O)6(p-Tos)2](p-Tos)2(H2O)3 where two tosylate groups coordinate to the lanthanide cation. It is another example how unusual coordination environments can be trapped by the use of ionic liquids. Trivalent lanthanide ions commonly exhibit high coordination numbers together with a widely flexible coordination environment. Their oxo-chelate complexes formed for example by β-diketonates or carboxylic acids are of interest to chemists, physicists, and material scientists because of their spectroscopic characteristics.1,2 Toluene-4sulfonate (tosylate, p-Tos-) is an interesting ligand because of its coordinating ability. Although it still is a comparatively weakly coordinating anion, it is stronger Lewis basic than, for example, triflate (trifluoromethanesulfonate, OTf-).3 Until now, several lanthanide toluene-4-sulfonates have been synthesized by dissolution of the respective oxide in aqueous toluene-4-sulfonic acid.4-7 Interestingly, the toluene-4-sulfonates have been the first examples where a change from a pure aqua coordination to a mixed aqua-ligand coordination was found to occur along the row of lanthanides. The larger lanthanides Ln ) La-Nd form compounds with a composition of [(Ln(H2O)9](p-Tos)3(H2O) where the lanthanide ion is solely coordinated by water. In contrast, the smaller lanthanides Ln ) Sm-Yb as well as Y crystallize from aqueous solution as compounds with a composition of [Ln(H2O)6(p-Tos)2](p-Tos)(H2O)3. Here the lanthanide is coordinated by six aqua ligands and two monodentately coordinating toluene-4sulfonate ligands.4,5 It has been realized that ionic liquids give the unique opportunity to trap unusual coordination environments when used as crystallization media.8 And indeed, when crystallizing europium toluene4-sulfonate from the ionic liquid 1-ethyl-3-methylimidazolium tosylate under ambient conditions a new polymorph of the hydrous europium(III) p-toluenesulfonate, bis-aqua-(p-toluenesulfonato-O)europium (III)-bis-p-toluenesulfonate dehydrate ([Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 (1)) was obtained along with the known [Ln(H2O)6(p-Tos)2](p-Tos)(H2O)3 (see Supporting Information for analysis of the bulk reaction product). This new compound where one p-Tos ligand coordinates to the metal center represents the missing structural link between [(Ln(H2O)9](p-Tos)3(H2O) with noncoordinating tosylate and [Ln(H2O)6(p-Tos)2](p-Tos)2(H2O)3 where two tosylate groups coordinate to the lanthanide metal cation. [Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 (1) was obtained from a solution of Eu(p-Tos)39 in (C2mim)(p-Tos) (1:2 molar ratio) under ambient conditions. Needle-shaped crystals of [Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 precipitated from this solution after three months * To whom correspondence should be addressed. E-mail: anja.mudring@ rub.de.
Table 1. Crystallographic Details for Compound 1 compound
1
formula fw space group a (Å) b (Å) c (Å) V (Å3) Z Dcalcd, (g cm-3) abs coeff (mm-1) reflns collected independent reflns/Rint F(000) GOF on F2 final R indices [I > 2σ(I)]: R1, wR2 R indices (all data): R1, wR2
C21H39EuO18S3 827.66 P212121 7.686(2) 16.470(3) 25.370(5) 3211.7(1) 4 1.712 2.223 39886 7115/0.0947 1680 1.068 0.0363, 0.0861 0.0394, 0.0886
at room temperature (see Supporting Information for the exact synthetic procedure).
Results and Discussion. [Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 crystallizes in the orthorhombic space group P212121 (No. 19) with four formula units in the unit cell (see Table 1). The asymmetric unit of [Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 contains one crystallographically independent Eu(III) ion, three tosylate anions, seven aqua ligands, and two crystal water molecules (see Figure 1). The europium (III) cation is coordinated by eight oxygen atoms, one belonging to a monodentately coordinating p-toluenesulfonate anion and seven oxygen atoms from coordinating water. The Eu-O interatomic distances range from 2.369(3) to 2.444(3) Å (see Table 2) and are close to those found in other europium sulfonates.6 The overall coordination environment of Eu(III) can best be viewed as a square antiprism. A variety of hydrogen bonds can be found in the crystal structure of [Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 which include O-H · · · O, C-H · · · O, and C-H · · · π hydrogen bonding involving the seven aqua ligands, the two crystal water molecules, and the sulfonic groups and toluene groups of the tosylate anion. The water molecules can serve as both hydrogen donor and acceptor, whereas the deprotonated sulfonic oxygen can only serve as a hydrogen acceptor.
10.1021/cg900025x CCC: $40.75 2009 American Chemical Society Published on Web 04/27/2009
2550
Crystal Growth & Design, Vol. 9, No. 6, 2009
Communications
Figure 1. ORTEP representation of the asymmetric unit of 1 (50% probability ellipsoid, hydrogen atoms are omitted for clarity). Table 2. Selected Bond Lengths [Å] in 1 Eu(1)-O(3W) Eu(1)-O(7W) Eu(1)-O(8W) Eu(1)-O(4W)
2.369(3) 2.376(3) 2.394(3) 2.393(3)
Eu(1)-O(6W) Eu(1)-O(5W) Eu(1)-O(9W) Eu(1)-O(4)
2.417(3) 2.413(3) 2.406(4) 2.444(3)
Table 3. O-H · · O Hydrogen-Bonding Interactions in 1, Lengths [Å] and Angles [°]a D-H · · · A
D-H
H· · ·A
D· · ·A
D-H · · · A
O3W-H3WA · · · O1_$4 O1W-H1WB · · · O6W_$2 O9W-H9WA · · · O1W_$3 O4W-H4WA · · · O2_$3 O5W-H5WB · · · O2_$4 O2W-H2WA · · · O3_$3 O3W-H3WB · · · O2W O2W-H2WB · · · O6_$3 O4W-H4WB · · · O9 O7W-H7WB · · · O5 O9W-H9WB · · · O5_$1 O5W-H5WA · · · O8_$1 O8W-H8WA · · · O6_$1 O6W-H6WB · · · O9 O7W-H7WA · · · O7_$3 O8W-H8WB · · · O3
0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85
1.96 2.22 2.07 2.02 2.14 1.99 1.78 2.05 1.89 2.04 1.95 1.92 1.92 1.96 1.90 2.00
2.696(5) 2.891(6) 2.874(6) 2.802(5) 2.924(5) 2.811(6) 2.621(5) 2.846(5) 2.696(6) 2.748(5) 2.781(5) 2.736(6) 2.732(5) 2.731(6) 2.713(5) 2.809(5)
144.6 135.5 158.6 152.1 154.2 161.1 170.4 155.1 159.1 140.7 166.1 161.0 160.5 150.4 158.5 158.3
Figure 2. O-H · · · O hydrogen bonds formed between water molecules and p-toluenesulfonate anions. CH3C6H4 groups were omitted for clarity. Symmetry codes for the generated atoms A: x - 1, y, z; B: x + 1, y, z; C: -x - 3, y - 1/2, -z + 3/2; D: -x - 4, y - 1/2, -z + 3/2. Table 4. C-H · · O Hydrogen-Bonding Interactions in 1, Lengths [Å] and Angles [°]a D-H · · · A
D-H
H· · ·A
D· · ·A
D-H · · · A
C11-H11A · · · O3 C15-H15C · · · O9_$1 C1-H1B · · · O5_$2 C1-H1C · · · O7_$3 C8-H8B · · · O9W_$4 C8-H8C · · · O7_$5 C15-H15A · · · O3W_$1
0.93 0.96 0.96 0.96 0.96 0.96 0.96
2.63 2.61 2.81 2.94 2.93 2.73 2.82
3.516(7) 3.353(9) 3.586(7) 3.889(11) 3.501(6) 3.496(7) 3.681(8)
159.3 134.1 138.3 171.6 119.2 136.8 149.9
a Operators for generating equivalent atoms: $1 x + 1/2, -y - 5/2, -z + 1; $2 x - 1/2, -y - 5/2, -z + 2; $3 -x - 7/2, -y - 2, z + 1/ 2; $4 x + 1/2, -y - 5/2, -z + 2; $5 -x - 5/2, -y - 2, z + 1/2.
a Operators for generating equivalent atoms: $1 x - 1, y, z; $2 x + 1, y, z; $3 -x - 3, y - 1/2, -z + 3/2; $4 -x - 4, y - 1/2, -z + 3/2.
Hydrogen bonds are an important factor for intermolecular interactions with an impact on structure, function, and dynamics of a vast number of chemical systems.10 The strong structure directing power of hydrogen bonding has been especially realized for molecular recognition11 and crystal engineering.12 In [Eu(pTos)(H2O)7][p-Tos]2(H2O)2, O-H · · · O bonds are the most prominent structure directing hydrogen bonds. The O · · · O interatomic distances range from 2.621(5) to 2.924(5) Å (see Table 3). The O-H · · · O angles range from 135.5 to 170.4°. Three types O-H · · · O hydrogen bonds are found in this structure which can be divided into two-centered, three-centered (or bifurcated), and four-centered (or trifurcated) (see Figure 2). It is observed that O3, O5, O9, O1w, and O6w form two-centered interactions, O3w, O4w, O5w, O7w, O8w, and O9w form three-centered hydrogen bonds, whereas O2w form four-centered interactions with O3w, O3 (symmetry code: -x - 3, y - 1/2, -z + 3/2), and O6 (symmetry code: -x - 3, y - 1/2, -z + 3/2). C-H · · · O hydrogen bonds have a wide range of geometries and strengths. In Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 the interatomic C · · · O distances range from 3.353(9) to 3.889(11) Å, and the C-H · · · O angles range from 119.2 to 171.6° (see Table 4), indicating that C-H · · · O interacts with the neighboring sulfonic groups and water, forming two intermolecular C-H · · · O hydrogen bonds (see Figure 3). The before-mentioned strong intermolecular O-H · · · O and C-H · · · O hydrogen bonds link the asymmetric units to twodimensional (2D) layers in the ab plane (see Figure 4a) with an
Figure 3. C-H · · · O hydrogen bonds in 1. Water molecules around europium(III) are omitted for clarity. Symmetry codes for the generated atoms A: x + 1/2, -y - 5/2, -z + 1; B: x - 1/2, -y - 5/2, -z + 2; C: -x - 7/2, -y - 2, z + 1/2; D: x + 1/2, -y - 5/2, -z + 2; E: -x - 5/2, -y - 2, z + 1/2.
interlayer distance of about 14.2 Å. These layers are further assembled into a three-dimensional (3D) supramolecular structure through intermolecular C-H · · · O hydrogen bonds and edge-toface C-H · · · π (or π · · · π) interactions ranging from 3.51 to 3.77 Å (see Figure 4b). In conclusion, this work describes the structural characterization of a new structure type of hydrated lanthanide tosylate, where just one tosylate ligand coordinates to the lanthanide cation. [Eu(p-Tos)(H2O)7][p-Tos]2(H2O)2 can be grasped as the missing link between the two known compositions found for hydrous lanthanide tosylates, [(Ln(H2O)9](p-Tos)3(H2O) and [Ln(H2O)6(p-Tos)2](p-Tos)(H2O)3 where no tosylate or two tosylate ions coordinate to the lanthanide ion. Furthermore, it is yet another example that unusual coordination environments can be achieved by crystallization from ionic liquids. We believe that hydrogen bonding is an important structure directing
Communications
Crystal Growth & Design, Vol. 9, No. 6, 2009 2551 procedure. This material is available free of charge via the Internet at http://pubs.acs.org.
References
Figure 4. (a) 2D layer in the ab-plane; (b) view of the structure of 1 down the b-axis. Hydrogen atoms are omitted for clarity. The EuO8 antiprism and sulfonate tetrahedra are shaded in purple and green, respectively. Eu, C, S, and O atoms are drawn as green, black, yellow, and red circles, respectively. Hydrogen bonds are drawn as dashed lines.
factor. It is well-known that ionic liquids are highly structure liquids due to the formation of interionic hydrogen bonds. In 1, itself substantial hydrogen bonds exist which include O-H · · · O, C-H · · · O, and C-H · · · π interactions. The O-H · · · O interactions are very strong and linear, whereas the C-H · · · O interactions are weaker (judging from the interatomic distance) and lack directionality.
Acknowledgment. Support by the DFG (Deutsche Forschungsgemeinschaft) and the Fonds der Chemischen Industrie through a Dozentenstipendium for AVM is gratefully acknowledged. Supporting Information Available: Crystallographic information file and details of crystal structure determination and the synthetic
(1) Greenwood, N. N.; Earnshow, A. Chemistry of the Elements; Pergamon Press: Oxford, 1985. (2) Dieke, G. H. Spectra and Energy LeVels of Rare Earth Ions in Crystals; John Wiley & Sons: New York, 1968. (3) Lawrence, G. A. AdV. Inorg. Chem. 1989, 34, 145. (4) Ohki, Y.; Suzuki, Y.; Takeuchi, T.; Ouchi, A. Bull. Chem. Soc. Jpn. 1988, 61, 393. (5) Faithfull, D. L.; Harrowfield, J. M.; Ogden, M. I.; Skelton, B. W.; Third, K.; White, A. H. Aust. J. Chem. 1992, 45, 583–594. (6) Jones, C.; Junk, P. C.; Smith, M. K.; Thomas, R. C. Z. Anorg. Allg. Chem. 2000, 626, 2491. (7) Hatano, M.; Takagi, E.; Arinobe, M.; Ishihara, K. J. Organomet. Chem. 2007, 692, 569. (8) (a) Hines, C. C.; Cocalia, V. A.; Rogers, R. D. Chem. Commun. 2007, 226. (b) Reichert, W. M.; Holbrey, J. D.; Vigour, K. B.; Morgan, T. D.; Broker, G. A.; Rogers, R. D. Chem. Commun. 2006, 4767. (c) Gutowski, K. E.; Cocalia, V. A.; Griffin, S. T.; Bridges, N. J.; Dixon, D. A.; Rogers, R. D. J. Am. Chem. Soc. 2007, 129, 526. (d) Babai, A.; Mudring, A.-V. Chem. Mater. 2005, 17, 6230. (e) Mudring, A.V.; Babai, A.; Arenz, S.; Giernoth, R. Angew. Chem., Int. Ed. 2005, 44, 5485. (f) Bhatt, A. I.; May, I.; Volkovich, V. A.; Collison, D.; Helliwell, M.; Polovov, I. B.; Lewin, R. G. Inorg. Chem. 2005, 44, 4934. (g) Arenz, S.; Babai, A.; Binnemans, K.; Driesen, K.; Giernoth, R.; Mudring, A.-V.; Nockemann, P. Chem. Phys. Lett. 2005, 402, 75. (h) Babai, A.; Mudring, A.-V. J. Alloys Compd. 2006, 418, 122. (i) Babai, A.; Mudring, A.-V. Inorg. Chem. 2005, 44, 8168. (j) Gaillard, C.; Billard, I.; Chaumont, A.; Mekki, S.; Ouadi, A.; Denecke, M. A.; Moutiers, G.; Wipff, G. Inorg. Chem. 2005, 44, 8355. (k) Chaumont, A.; Wipff, G. Phys. Chem. Chem. Phys. 2003, 5, 3481. (l) Chaumont, A.; Wipff, G. J. Phys. Chem. B 2004, 108, 3311. (m) Gaillard, C.; Chaumont, A.; Billard, I.; Hennig, C.; Ouadi, A.; Wipff, G. Inorg. Chem. 2007, 46, 4815. (9) Eu(p-Tos)3 was synthesized by dissolving a slight excess of europium oxide (Eu2O3) in aqueous toluene-4-sulfonic acid and subsequent removal of the excess Eu2O3 and liquid phase. The obtained salt was dried for 48 h under vacuum. (10) Steiner, T. Angew. Chem., Int. Ed. 2002, 41, 48. (11) Desiraju, G. R. Angew. Chem. Int. Ed. Ed. 1995, 34, 2311. (12) Desiraju, G. R. Acc. Chem. Res. 2002, 35, 565.
CG900025X
