Received 30 August 2013
A two-dimensional hydrogen-bonded water layer in the structure of a cobalt(III) cubane complex
A tetranuclear CoIII oxide complex with cubane topology, tetrakis(2,2'-bipyridine-2N,N')di-2-carbonato-4O:O'-tetra-3-oxido-tetracobalt(III) pentadecahydrate, [Co4(CO3)2O4(C10H8N2)4]·15H2O, with an unbounded hydrogen-bonded water layer, has been synthesized by reaction of CoCO3 and 2,2'-bipyridine. The solvent water molecules form a hydrogen-bonded net with tetrameric and pentameric water clusters as subunits. The Co4O4 cubane-like cores are sandwiched between the water layers, which are further stacked into a three-dimensional metallo-supramolecular network.
In the past few years, metal complexes containing hydrogen-bonded water clusters have attracted a great deal of attention in the fields of supramolecular chemistry and crystal engineering, because studying the behaviour of water clusters can provide insight into the mutual interaction of unusual properties which are of importance in many physical, chemical and biological processes (Yang et al., 2008; Moorthy et al., 2002; Wu & Lin, 2005; Liu et al., 2007; Cheng et al., 2006; Jin & Che, 2007). The theoretical and experimental study of flexible hydrogen-bonded water clusters can provide direct information on how the clusters are formed and how they interlink in various geometries under diverse environments (Ghosh & Bharadwaj, 2004; Atwood et al., 2001; Müller et al., 2003; Meng et al., 2010). During the past decade, a variety of water clusters, such as trimers (Ghosh & Bharadwaj, 2005), tetramers (Zuhayra et al., 2006), pentamers (Zabel et al., 1986), hexamers (Saha & Nangia, 2006), octamers (Khatua et al., 2010), decamers (Yoshizawa et al., 2005), dodecamers (Song & Ma, 2007), tetradecamers (Ghosh et al., 2005), hexadecamers (Bi et al., 2009) and octadecamers (Luan et al., 2006), and one-dimensional chains (Saha & Nangia, 2005), one-dimensional tapes (Cheng et al., 2006), two-dimensional layers (Zhang et al., 2005) and three-dimensional structures (Carballo et al., 2005) have been reported. However, detailed studies of the aggregation patterns of smaller subunits within larger water clusters are less numerous (Yang et al., 2008; Li et al., 2008). In this paper, we present the structure of a cubane-like tetranuclear oxide-bridged cobalt(III) complex, namely [Co4(CO3)2(3-O)4(bpy)4]·15H2O (bpy is 2,2'-bipyridine), (I), including isolated two-dimensional water cluster layers.
| || Figure 1 |
The molecular structure of the cubane-like tetranuclear oxide-bridged cobalt(III) cluster of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 45% probability level. [Symmetry code: (i) x, -y + , z.]
| || Figure 2 |
The structure and hydrogen-bond connectivity of the (H2O)14 cluster of (I). Green dashed lines indicate hydrogen-bonding interactions within tetrameric and pentameric water cluster units, and purple dashed lines represent hydrogen bonds between the pendent water molecules and the tetrameric and pentameric units in the (H2O)14 cluster. [Symmetry code: (i) x, -y + , z.]
| || Figure 3 |
The hydrogen-bonded network of the supramolecular water layer of (I). Dashed lines indicate hydrogen bonds. [Symmetry codes: (i) x, -y + , z; (ii) x, y, z + 1; (iv) -x, -y + 1, -z + 1.]
| || Figure 4 |
The three-dimensional supramolecular structure of (I). Green dashed lines indicate hydrogen-bonding interactions within the two-dimensional water cluster layers and purple dashed lines represent hydrogen bonds between the Co4O4 cores and the water clusters.
All chemicals and solvents were commercially available and were used without further purification. A purple precipitate resulted from the addition of Na2CO3 (1.0 ml, 1.0 M) to an aqueous solution of CoCl2·6H2O (0.1594 g, 0.67 mmol) in H2O (5 ml); it was separated by centrifugation and washed with distilled water four times, then transferred into a solution of 2,2'-bipyridine (0.1062 g, 0.67 mmol) in methanol (10 ml) and water (10 ml). To the resulting red solution (pH = 11.24), Na2CO3 (1.0 ml, 1.0 M) was added dropwise to adjust the pH to 12.21. The mixture obtained was allowed to stand at room temperature for 12 d to afford dark-red needle-shaped crystals of (I).
Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms bonded to C atoms were placed in geometrically calculated positions and refined using a riding model, with C-H = 0.93 Å and Uiso(H) = 1.2Ueq(C). H atoms attached to O atoms were found in a difference Fourier synthesis and refined with the O-H and intramolecular HH distances restrained to 0.85 (1) and 1.35 (1) Å, respectively, and with Uiso(H) = 1.5Ueq(O), while the H atoms of the multiply split O19 atom could not be positioned reliably and were omitted from the structure model. Finally, all non-H atoms, except O19, were refined with anisotropic displacement parameters. Atom O19 was found to be split over four sites, which were assigned fractional occupancies summing to 0.5 and a common variable isotropic displacement parameter.
Hydrated complex (I) crystallizes in the orthorhombic space group Pnma, with a hydrogen-bonded water layer separating molecules of the cluster, which has a Co4O4 cubane core (Fig. 1). The CoIII cations and O atoms are located at alternating corners of a distorted cube. Each CoIII cation is coordinated by two bpy N atoms, one carbonate O atom and three oxide O atoms, forming an octahedral CoN2O4 coordination geometry. Atom Co1 lies in a general posiiton (Wyckoff site 8d), while atoms Co2 and Co3 are halved by a mirror plane (Wyckoff sites 4c). The Co1-N/O bond lengths span the range 1.876 (2)-1.950 (2) Å, and the cisoid and transoid N/O-Co1-N/O angles span the ranges 81.68 (10)-97.73 (10) and 172.79 (9)-177.04 (10)°, respectively. For atom Co2, the corresponding ranges are 1.876 (2)-1.943 (3) Å, 81.61 (16)-96.77 (10) and 173.63 (12)-176.58 (10)°, and for atom Co3 they are 1.878 (2)-1.947 (2) Å, 81.05 (15)-98.05 (10) and 172.21 (13)-176.77 (10)°. All of these parameters are normal and confirm a slightly distorted octahedral coordination for the cations.
The cuboidal core of the cluster is distorted, with all the O-Co-O angles being smaller than 90° and all the Co-O-Co angles being larger than 90°. The CoCo distances within the cubane vary from 2.6645 (9) to 2.8582 (7) Å (Table 2). The resulting Co4O4 cubane-like cores are capped by two crystallographically distinct carbonate ligands, both of them bisected by a mirror plane.
It is interesting to note that ten symmetry-independent solvent water molecules, by co-operative hydrogen-bonding interactions, form a two-dimensional water network comprised of tetrameric and pentameric water clusters as subunits (Fig. 2). The water molecules at O10, O14, O14i and O17 [symmetry code: (i) x, -y + , z] form a cyclic tetrameric cluster through hydrogen bonds. The water molecules containing O10 and O17 form pairs of mirror-symmetric hydrogen bonds, viz. O10-H10AO14 and O17-H17AO14, respectively (see Fig. 2 and Table 3 for details). With the inclusion of water atoms O11, O12, O16 and O16i, a cyclic tetrameric water cluster is formed. In these tetrameric clusters, the average OO separation (2.84 Å) is comparable with the value of 2.85 Å in liquid water, where the OOO angles are in the range 73.6-98.4° (Eisenberg & Kauzmann, 1969). The hydrogen bonds within the pentameric core involve atoms O10, O12, O14, O15 and O16, and their associated H atoms. As far as the pentamer is concerned, the OOO angles are in the range 95.8 (2)-112.8 (3)° and the OO distances range from 2.756 (5) to 2.840 (6) Å (average 2.796 Å), slightly longer than those observed in ice Ih (2.759 Å at 200 K; Eisenberg & Kauzmann, 1969).
The tetrameric water clusters and the two crystallographically equivalent pentameric water clusters are edge-shared into (H2O)14 clusters (Fig. 2), in which the pentameric clusters form hydrogen-bonding interactions with solvent water molecule O13, and the crystallographically independent tetrameric water cluster is a hydrogen-bond acceptor in an interaction with O9 and is a donor to O18. Neighbouring (H2O)14 clusters are joined together by hydrogen-bonding interactions through two independent six-membered water rings [one formed by atoms O13, O14, O15, O13iv, O14iv and O15iv, and the other formed by atoms 09ii, O10ii, O11, O14ii, O17ii and O18; symmetry codes: (ii) x, y, z + 1; (iv) -x, -y + 1, -z + 1], extending into a two-dimensional layer of water clusters (Fig. 3). Interestingly, the Co4O4 cubane-like cores are sandwiched between these two-dimensional water cluster layers. Solvent molecules O9, O12, O13 and O15 donate H atoms to carbonate atoms O1, O2, O3 and O5 (Table 3). Due to this connection between the Co4O4 cubane-like core and the two-dimensional water cluster layers, the overall structure of (I) can be considered as a three-dimensional metallo-supramolecular network (Fig. 4).
Supporting information for this paper is available from the IUCr electronic archives (Reference: BG3165 ).
This project was supported by the K. C. Wong Magna Fund of Ningbo University.
Atwood, J. L., Barbour, L. J., Ness, T. J., Raston, C. L. & Raston, P. L. (2001). J. Am. Chem. Soc. 123, 7192-7193.
Bi, Y., Liao, W., Zhang, H. & Li, D. (2009). CrystEngComm, 11, 1213-1216.
Carballo, R., Covelo, B., Lodeiro, C. & Vázquez-López, E. M. (2005). CrystEngComm, 7, 294-296.
Cheng, L., Lin, J. B., Gong, J. Z. & Sun, A. P. (2006). Cryst. Growth Des. 12, 2739-2746.
Eisenberg, K. D. & Kauzmann, W. (1969). In The Structure and Properties of Water. Oxford University Press.
Ghosh, S. K. & Bharadwaj, P. K. (2004). Angew. Chem. Int. Ed. 43, 3577-3580.
Ghosh, S. K. & Bharadwaj, P. K. (2005). Inorg. Chem. 44, 5553-5555.
Ghosh, S. K., Ribas, J., Fallah, M. S. E. & Bharadwaj, P. K. (2005). Inorg. Chem. 44, 3856-3862.
Higashi, T. (1995). ABSCOR. Rigaku Corporation, Tokyo, Japan.
Jin, Y. & Che, Y.-X. (2007). Inorg. Chem. Commun. 10, 514-516.
Khatua, S., Kang, J., Huh, J. O., Hong, C. S. & Churchill, D. G. (2010). Cryst. Growth Des. 10, 327-334.
Li, C.-H., Huang, K.-L., Dou, J.-M., Chi, Y.-N., Xu, Y.-Q., Shen, L., Wang, D.-Q. & Hu, C.-W. (2008). Cryst. Growth Des. 8, 3141-3143.
Liu, J.-Q., Wang, Y.-Y., Liu, P. & Wu, W.-P. (2007). Inorg. Chem. Commun. 10, 343-347.
Luan, X., Chu, Y., Wang, Y., Li, D., Liu, P. & Shi, Q. Z. (2006). Cryst. Growth Des. 6, 812-814.
Meng, Q.-G., Yan, S.-T., Kong, G.-Q., Yang, X.-L. & Wu, C.-D. (2010). CrystEngComm, 12, 688-690.
Moorthy, J. N., Natarajan, R. & Venugopalan, P. (2002). Angew. Chem. Int. Ed. 41, 3417-3420.
Müller, A., Krickemeyer, E., Bögge, H., Schmidtmann, M., Botar, B. & Talismanova, M. O. (2003). Angew. Chem. Int. Ed. 42, 2085-2090.
Rigaku (1998). RAPID-AUTO. Rigaku Corporation, Tokyo, Japan.
Rigaku/MSC (2004). Crystal Structure. Rigaku/MSC Inc., The Woodllands, Texas, USA.
Saha, B. K. & Nangia, A. (2005). Chem. Commun. pp. 3024-3026.
Saha, B. K. & Nangia, A. (2006). Chem. Commun. pp. 1825-1827.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Song, H.-H. & Ma, B.-Q. (2007). CrystEngComm, 9, 625-627.
Wu, C.-D. & Lin, W.-B. (2005). Angew. Chem. Int. Ed. 44, 1958-1961.
Yang, A.-H., Zhang, H., Gao, H.-L., Zhang, W.-Q., He, L. & Cui, J.-Z. (2008). Cryst. Growth Des. 8, 3354-3359.
Yoshizawa, M., Kusukawa, T., Kawano, M., Ohhara, T., Tanaka, I., Kurihara, K., Niimura, N. & Fujita, M. (2005). J. Am. Chem. Soc. 127, 2798-2799.
Zabel, V., Saenger, W. & Mason, S. A. (1986). J. Am. Chem. Soc. 108, 3664-3673.
Zhang, J.-P., Huang, X.-C., Lin, Y.-Y. & Chen, X.-M. (2005). Inorg. Chem. 44, 3146-3150.
Zuhayra, M., Kampen, W. U., Henze, E., Soti, Z., Zsolnai, L., Huttner, G. & Oberdorfer, F. (2006). J. Am. Chem. Soc. 128, 424-425.