- Email: [email protected]
A peculiar heterotrimetallic MnII–CoII–NiII complex: Synthesis, crystal structure and magnetic properties
Inorganic Chemistry Communications 11 (2008) 714–716
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
A peculiar heterotrimetallic MnII–CoII–NiII complex: Synthesis, crystal structure and magnetic properties Gong-Feng Xu a, Bin Liu b, Hai-Bin Song c, Qing-Lun Wang a, Shi-Ping Yan a, Dai-Zheng Liao a,d,* a
Department of Chemistry, Nankai University, Tianjin 300071, PR China Tianjin Medical College, Tianjin 300052, PR China c Department of Chemistry, The State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China d State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China b
a r t i c l e
i n f o
Article history: Received 1 February 2008 Accepted 4 March 2008 Available online 18 March 2008
a b s t r a c t The first complex [Mn(H2O)6][NiCo(TTHA)(H2O)2] 4H2O 1 (TTHA6 = triethylenetetraminehexaacetate) containing MnII–CoII–NiII three different 3d metal ions is synthesized and magnetic measurement suggests that ferromagnetic interactions occur between Ni2+ ions and rarely found low-spin Co2+ ions. Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Triethylenetetraminehexaacetic acid (H6TTHA) MnII–CoII–NiII complex Crystal structure Ferromagnetic interactions
During the last several decades heteropolymetallic systems have drawn attention particularly of inorganic chemists for advanced applications including catalysis [1], biological systems [2] and molecular magnetism [3]. Although there is already a long history and a prolific literature on the subject of heteropolymetallic complexes, most of them contain only two different kinds of metals. And heterotrinuclear complexes containing three different kinds of metal ions [4], especially three different 3d metal ions have been investigated rarely [5]. On the other hand, the great attention has been paid to the polyaminopolycarboxylate complexes because of their industrial, environmental, and biological applications [6]. But there are only a few of them studied by magnetic measurements [7], especially for H6TTHA, which is a multidentate ligand having two equivalent coordinated vacant sites (skeleton in Fig. 1). The report of the complex containing TTHA6 is limited, especially those containing different metal ions [8]. In view of these, we decided to prepare new heteronuclear complex using H6TTHA as bridged ligand [11]. Herein we report the synthesis, crystal structure and magnetic properties of this complex with formula [Mn(H2O)6][NiCo(TTHA)(H2O)2] 4H2O 1, which
* Corresponding author. Address: Department of Chemistry, Nankai University, Tianjin 300071, PR China. Tel.: +86 22 23509957; fax: +86 22 23502779. E-mail address: [email protected] (D.-Z. Liao). 1387-7003/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2008.03.003
is the first complex containing MnII–CoII–NiII three different 3d metal ions to our knowledge. X-ray crystallography reveals that in 1, the structure is built up with discrete dimers Co–Ni, hexahydrated Mn2+ ions and water molecules. In the dimer Co and Ni are equivalent asymmetrically (As we all know they are unrecognizable crystallographically, so in Fig. 2 it is labeled as Co/Ni). The Co/Ni ion is sixfold coordinated by four oxygen atoms originating from the carboxylate of TTHA6 and water molecule (Co/Ni–O distances: 2.043–2.072 Å) and two nitrogen atoms stemming from TTHA6 (Co/Ni–N distances: 2.108 and 2.165 Å) and the bond lengths are compared well with the report ones [8]. The Mn ion is coordinated with six water molecules (Mn–O distances: 2.132–2.200 Å). The three-dimensional frameworks of compound 1 is constructed by intermolecular hydrogen bond interactions (Fig. 3). The Co–Ni dimers join together end to end by hydrogen bond (O3AE O7AD distances: 2.776 Å) to form a zigzag chain structure. Each hexahydrate Mn ions are linked through hydrogen bond (O–O distances: 2.682–2.776 Å) by six oxygen atoms that come from four Co–Ni dimers. These two kinds of hydrogen bond interactions together form a 2D layer structure as shown in Fig. 3a and b. The 2D layers are linked further with hydrogen bond interactions
Electronic Supplementary Information (ESI) available: crystallographic data table for complex 1.
715
G.-F. Xu et al. / Inorganic Chemistry Communications 11 (2008) 714–716
OH O OH
OH
O N
O
N N
O N O
HO
OH
O OH Fig. 1. The skeleton of H6TTHA.
Fig. 2. ORTEP plot of complex 1 at the 30% probability level. (Hydrogen atoms and uncoordinated water molecules are not displayed for clarity).
vtot ¼ vCo—Ni þ vMn
Ng 2 b2 5 5 þ1 vMn ¼ 3kðT hÞ 2 2 Ng 2 b2 10 þ expð3J=kTÞ vCo—Ni ¼ 4kðT hÞ 2 þ expð3J=kTÞ
Fig. 3. Hydrogen interactions in compound 1.
9.0 2.0 7.5
3
1.0
6.0
μeff / B.M.
-1
1.5
χM / cm mol
between carboxylate oxygen atoms of TTHA6 and isolated water molecules to form a three-dimensional system as depicted in Fig. 3c. Variable temperature magnetic susceptibility measurement (4– 300 K) under the field of 1000 G was performed (Fig. 4). The r.t. leff value (7.15 B.M.) is slightly larger than the spin-only one (6.78 B.M.) for one Mn2+ ion(6A1g), one low-spin Co2+ ion(2A1g) and one Ni2+ ion(3A2g) supposed g = 2 which is probably due to the mixing of higher ligand-field terms into the ground term through spin-orbit coupling for low-spin Co2+ and Ni2+ ions. The curve progression suggests a ferromagnetic behavior within trinuclear complex. Obviously, a strictly quantitative theoretical treatment of magnetic properties for such asymmetric heterotrinuclear system cannot be carried out due to the complexity of the problem. However, to obtain a rough quantitative estimate of the magnetic interaction parameters, we assume that the total magnetic susceptibility vtot is given by the sum of isolated Mn2+ vMn and binuclear Co–Ni unit vCo–Ni derived based on the isotropic spin b ¼ 2J b Hamiltonian H S Co b S Ni ,
0.5 4.5 0.0 0
50
100
150
200
250
300
3.0
T/K Fig. 4. Temperature dependence of vM and vMT in compound 1 under 1000 G.
716
G.-F. Xu et al. / Inorganic Chemistry Communications 11 (2008) 714–716
where J is magnetic interaction parameter between Co2+ and Ni2+ ions within binuclear unit. The Weiss constant, h, is introduced to roughly simulate the magnetic interaction between the other paramagnetic species [9]. Based on the occupancy of the magnetic orbitals, it is reasonable to expect ferromagnetic interaction between Ni2+ and Co2+ ions to occur. The Ni2+ ion has two unpaired electrons on the dz2 and dx2–y2 orbitals. In the case of low-spin Co2+ ions under a slightly distorted octahedron have unpaired electron on the dxz or dyz orbitals [10]. The orthogonality of dz2, dx2–y2 and dxz or dyz orbitals is expected to favor ferromagnetic interactions [3b]. Using least-square method to fit the experimental data leads to the satisfactory result of g = 2.12, J = 17.72 cm1, h = 0.37 K with P P R = 2.64 104 (defined as R ¼ ðvobs vcalc Þ2 = v2obs ). In conclusion, the first peculiar complexes containing simultaneously MnII–CoII–NiII three different 3d metal ions is synthesized and variable temperature magnetic susceptibility measurement suggests ferromagnetic interactions occur between Ni2+ ions and rarely found low-spin Co2+ ions. The work is supported by the National Natural Science Foundation of China (Nos. 20631030 and 20601014) and National Basic Research Program of China (973 Program, 2007CB815305). Appendix A. Supplementary material CCDC 298014 contains the supplementary crystallographic data for a single crystal of the title complex (dimensions, 0.40 0.30 0.20 mm) were collected at room temperature with a Enraf–Nonius CAD-4 diffractometer with Mo–Ka radiation (k = 0.71073 Å). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_ request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2008.03.003. References [1] (a) W.H. Zhang, S. J Luo, F. Fang, Q.S. Chen, H.W. Hu, X.S. Jia, H.B. Zhai, J. Am. Chem. Soc. 127 (2005) 18;
[2] [3]
[4] [5]
[6] [7]
[8]
[9] [10] [11]
(b) S. Cenini, E. Galloa, A. Caselli, F. Ragaini, S. Fantauzzi, C. Piangiolino, Coord. Chem. Rev. 250 (2006) 1234. J.N. Chan, Z.Y. Huang, M.E. Merrifield, M.T. Salgado, M.J. Stillman, Coord. Chem. Rev. 233 (2002) 319. (a) O. Kahn, Struct. Bond. 68 (1987) 89; (b) O. Kahn, Molecular Magnetism, Wiley-VCH, Weinheim, 1993; (c) J.S. Miller, M. Drillon, Magnetism: Molecules to Materials IV, Wiley-VCH, Weinheim, 2002. H.Z. Kou, B.C. Zhou, S. Gao, R.J. Wang, Angew. Chem. Int. Ed. 42 (2003) 3288. (a) C.P. Berlinguette, K.R. Dunbar, Chem. Commun. (2005) 2451; (b) D.S. Nesterov, V.N. Kokozay, V.V. Dyakonenko, O.V. Shishkin, J. Jezierska, A. Ozarowski, A.M. Kirillov, M.N. Kopylovich, A.J.L. Pombeiro, Chem. Commun. (2006) 4605. (a) T. Egli, J. Biosci. Bioeng. 92 (2001) 89; (b) M. Sillanpaa, M. Orama, J. Ramo, A. Oikari, Sci. Total Environ. 267 (2001) 23. (a) E. Coronado, M. Drillon, A. Fuert, D. Beltran, A. Mosset, J. Galy, J. Am. Chem. Soc. 108 (1986) 900; (b) E. Coronado, M. Drillon, P.R. Nugteren, L.J. De Jongh, D. Beltran, R. Georges, J. Am. Chem. Soc. 111 (1989) 3874. (a) L.J. Song, J. Zhang, Z.R. Tan, W.G. Wang, Z.F. Ju, Acta Cryst. E59 (2003) m867; (b) W. Shi, Y. Dai, B. Zhao, H.B. Song, H.G. Wang, P. Cheng, et al., Inorg. Chem. Commun. 9 (2006) 192. Y. Liao, W.W. Shum, J.S. Miller, J. Am. Chem. Soc. 124 (2002) 9336. Y. Nishida, S. Kida, Bull. Chem. Soc. Jpn. 45 (1972) 461. Synthesis of the Compound 1: The 10 mL aqueous solution of 57 mg (0.2 mmol) Mn(NO3)2 6H2O, 58 mg (0.2 mmol) Co(NO3)2 6H2O and 58 mg (0.2 mmol) Ni(NO3)2 6H2O was added dropwise into another 10 mL aqueous solution which contains 99 mg (0.2 mmol) H6TTHA and 48 mg (1.2 mmol) NaOH while stirring. Then the mixture was placed in an EtOH atmosphere without disturbance using the method of vapour diffusion. After a few weeks later, with the gaseous EtOH diffusing into the aqueous solution small light blue-violet single crystals suitable for X-ray analysis were formed (91 mg, 52% based on Mn). Elemental analysis of C18H48N4O24CoMnNi (877.18): calcd. C 24.65, H 5.52, N 6.39, Mn 6.26, Co 6.72, Ni 6.69; found C 24.76, H 5.43, N 6.07, Mn 6.66, Co 7.24, Ni 7.39. IR(KBr disk, cm1): 3250(b, mOH), 1580(b, mas(CO2)), 1325(m, ms(CO2)), 1100(m, mC–N). Absorption corrections were applied via an empirical correction (w scans; transmission factors varied from 0.59 to 0.76). The structure was solved by direct methods using the program SHELXS97 and refined on F2 by full matrix least-squares procedures using the program SHELXL97 and the residual factors R1 and wR2 is 0.0625, 0.1693, respectively. The non-hydrogen atoms were refined anisotropically and the hydrogen atoms were allowed to ride over their parent atoms. The hydrogen atoms on the water molecules could not be located. According to the elemental analysis data the proportional of Co:Ni is 1:1. The possibility that both the Co and the Ni positions are mixed Co/Ni sites cannot be excluded.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
A peculiar heterotrimetallic MnII–CoII–NiII complex: Synthesis, crystal structure and magnetic properties Gong-Feng Xu a, Bin Liu b, Hai-Bin Song c, Qing-Lun Wang a, Shi-Ping Yan a, Dai-Zheng Liao a,d,* a
Department of Chemistry, Nankai University, Tianjin 300071, PR China Tianjin Medical College, Tianjin 300052, PR China c Department of Chemistry, The State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China d State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China b
a r t i c l e
i n f o
Article history: Received 1 February 2008 Accepted 4 March 2008 Available online 18 March 2008
a b s t r a c t The first complex [Mn(H2O)6][NiCo(TTHA)(H2O)2] 4H2O 1 (TTHA6 = triethylenetetraminehexaacetate) containing MnII–CoII–NiII three different 3d metal ions is synthesized and magnetic measurement suggests that ferromagnetic interactions occur between Ni2+ ions and rarely found low-spin Co2+ ions. Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Triethylenetetraminehexaacetic acid (H6TTHA) MnII–CoII–NiII complex Crystal structure Ferromagnetic interactions
During the last several decades heteropolymetallic systems have drawn attention particularly of inorganic chemists for advanced applications including catalysis [1], biological systems [2] and molecular magnetism [3]. Although there is already a long history and a prolific literature on the subject of heteropolymetallic complexes, most of them contain only two different kinds of metals. And heterotrinuclear complexes containing three different kinds of metal ions [4], especially three different 3d metal ions have been investigated rarely [5]. On the other hand, the great attention has been paid to the polyaminopolycarboxylate complexes because of their industrial, environmental, and biological applications [6]. But there are only a few of them studied by magnetic measurements [7], especially for H6TTHA, which is a multidentate ligand having two equivalent coordinated vacant sites (skeleton in Fig. 1). The report of the complex containing TTHA6 is limited, especially those containing different metal ions [8]. In view of these, we decided to prepare new heteronuclear complex using H6TTHA as bridged ligand [11]. Herein we report the synthesis, crystal structure and magnetic properties of this complex with formula [Mn(H2O)6][NiCo(TTHA)(H2O)2] 4H2O 1, which
* Corresponding author. Address: Department of Chemistry, Nankai University, Tianjin 300071, PR China. Tel.: +86 22 23509957; fax: +86 22 23502779. E-mail address: [email protected] (D.-Z. Liao). 1387-7003/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2008.03.003
is the first complex containing MnII–CoII–NiII three different 3d metal ions to our knowledge. X-ray crystallography reveals that in 1, the structure is built up with discrete dimers Co–Ni, hexahydrated Mn2+ ions and water molecules. In the dimer Co and Ni are equivalent asymmetrically (As we all know they are unrecognizable crystallographically, so in Fig. 2 it is labeled as Co/Ni). The Co/Ni ion is sixfold coordinated by four oxygen atoms originating from the carboxylate of TTHA6 and water molecule (Co/Ni–O distances: 2.043–2.072 Å) and two nitrogen atoms stemming from TTHA6 (Co/Ni–N distances: 2.108 and 2.165 Å) and the bond lengths are compared well with the report ones [8]. The Mn ion is coordinated with six water molecules (Mn–O distances: 2.132–2.200 Å). The three-dimensional frameworks of compound 1 is constructed by intermolecular hydrogen bond interactions (Fig. 3). The Co–Ni dimers join together end to end by hydrogen bond (O3AE O7AD distances: 2.776 Å) to form a zigzag chain structure. Each hexahydrate Mn ions are linked through hydrogen bond (O–O distances: 2.682–2.776 Å) by six oxygen atoms that come from four Co–Ni dimers. These two kinds of hydrogen bond interactions together form a 2D layer structure as shown in Fig. 3a and b. The 2D layers are linked further with hydrogen bond interactions
Electronic Supplementary Information (ESI) available: crystallographic data table for complex 1.
715
G.-F. Xu et al. / Inorganic Chemistry Communications 11 (2008) 714–716
OH O OH
OH
O N
O
N N
O N O
HO
OH
O OH Fig. 1. The skeleton of H6TTHA.
Fig. 2. ORTEP plot of complex 1 at the 30% probability level. (Hydrogen atoms and uncoordinated water molecules are not displayed for clarity).
vtot ¼ vCo—Ni þ vMn
Ng 2 b2 5 5 þ1 vMn ¼ 3kðT hÞ 2 2 Ng 2 b2 10 þ expð3J=kTÞ vCo—Ni ¼ 4kðT hÞ 2 þ expð3J=kTÞ
Fig. 3. Hydrogen interactions in compound 1.
9.0 2.0 7.5
3
1.0
6.0
μeff / B.M.
-1
1.5
χM / cm mol
between carboxylate oxygen atoms of TTHA6 and isolated water molecules to form a three-dimensional system as depicted in Fig. 3c. Variable temperature magnetic susceptibility measurement (4– 300 K) under the field of 1000 G was performed (Fig. 4). The r.t. leff value (7.15 B.M.) is slightly larger than the spin-only one (6.78 B.M.) for one Mn2+ ion(6A1g), one low-spin Co2+ ion(2A1g) and one Ni2+ ion(3A2g) supposed g = 2 which is probably due to the mixing of higher ligand-field terms into the ground term through spin-orbit coupling for low-spin Co2+ and Ni2+ ions. The curve progression suggests a ferromagnetic behavior within trinuclear complex. Obviously, a strictly quantitative theoretical treatment of magnetic properties for such asymmetric heterotrinuclear system cannot be carried out due to the complexity of the problem. However, to obtain a rough quantitative estimate of the magnetic interaction parameters, we assume that the total magnetic susceptibility vtot is given by the sum of isolated Mn2+ vMn and binuclear Co–Ni unit vCo–Ni derived based on the isotropic spin b ¼ 2J b Hamiltonian H S Co b S Ni ,
0.5 4.5 0.0 0
50
100
150
200
250
300
3.0
T/K Fig. 4. Temperature dependence of vM and vMT in compound 1 under 1000 G.
716
G.-F. Xu et al. / Inorganic Chemistry Communications 11 (2008) 714–716
where J is magnetic interaction parameter between Co2+ and Ni2+ ions within binuclear unit. The Weiss constant, h, is introduced to roughly simulate the magnetic interaction between the other paramagnetic species [9]. Based on the occupancy of the magnetic orbitals, it is reasonable to expect ferromagnetic interaction between Ni2+ and Co2+ ions to occur. The Ni2+ ion has two unpaired electrons on the dz2 and dx2–y2 orbitals. In the case of low-spin Co2+ ions under a slightly distorted octahedron have unpaired electron on the dxz or dyz orbitals [10]. The orthogonality of dz2, dx2–y2 and dxz or dyz orbitals is expected to favor ferromagnetic interactions [3b]. Using least-square method to fit the experimental data leads to the satisfactory result of g = 2.12, J = 17.72 cm1, h = 0.37 K with P P R = 2.64 104 (defined as R ¼ ðvobs vcalc Þ2 = v2obs ). In conclusion, the first peculiar complexes containing simultaneously MnII–CoII–NiII three different 3d metal ions is synthesized and variable temperature magnetic susceptibility measurement suggests ferromagnetic interactions occur between Ni2+ ions and rarely found low-spin Co2+ ions. The work is supported by the National Natural Science Foundation of China (Nos. 20631030 and 20601014) and National Basic Research Program of China (973 Program, 2007CB815305). Appendix A. Supplementary material CCDC 298014 contains the supplementary crystallographic data for a single crystal of the title complex (dimensions, 0.40 0.30 0.20 mm) were collected at room temperature with a Enraf–Nonius CAD-4 diffractometer with Mo–Ka radiation (k = 0.71073 Å). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_ request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2008.03.003. References [1] (a) W.H. Zhang, S. J Luo, F. Fang, Q.S. Chen, H.W. Hu, X.S. Jia, H.B. Zhai, J. Am. Chem. Soc. 127 (2005) 18;
[2] [3]
[4] [5]
[6] [7]
[8]
[9] [10] [11]
(b) S. Cenini, E. Galloa, A. Caselli, F. Ragaini, S. Fantauzzi, C. Piangiolino, Coord. Chem. Rev. 250 (2006) 1234. J.N. Chan, Z.Y. Huang, M.E. Merrifield, M.T. Salgado, M.J. Stillman, Coord. Chem. Rev. 233 (2002) 319. (a) O. Kahn, Struct. Bond. 68 (1987) 89; (b) O. Kahn, Molecular Magnetism, Wiley-VCH, Weinheim, 1993; (c) J.S. Miller, M. Drillon, Magnetism: Molecules to Materials IV, Wiley-VCH, Weinheim, 2002. H.Z. Kou, B.C. Zhou, S. Gao, R.J. Wang, Angew. Chem. Int. Ed. 42 (2003) 3288. (a) C.P. Berlinguette, K.R. Dunbar, Chem. Commun. (2005) 2451; (b) D.S. Nesterov, V.N. Kokozay, V.V. Dyakonenko, O.V. Shishkin, J. Jezierska, A. Ozarowski, A.M. Kirillov, M.N. Kopylovich, A.J.L. Pombeiro, Chem. Commun. (2006) 4605. (a) T. Egli, J. Biosci. Bioeng. 92 (2001) 89; (b) M. Sillanpaa, M. Orama, J. Ramo, A. Oikari, Sci. Total Environ. 267 (2001) 23. (a) E. Coronado, M. Drillon, A. Fuert, D. Beltran, A. Mosset, J. Galy, J. Am. Chem. Soc. 108 (1986) 900; (b) E. Coronado, M. Drillon, P.R. Nugteren, L.J. De Jongh, D. Beltran, R. Georges, J. Am. Chem. Soc. 111 (1989) 3874. (a) L.J. Song, J. Zhang, Z.R. Tan, W.G. Wang, Z.F. Ju, Acta Cryst. E59 (2003) m867; (b) W. Shi, Y. Dai, B. Zhao, H.B. Song, H.G. Wang, P. Cheng, et al., Inorg. Chem. Commun. 9 (2006) 192. Y. Liao, W.W. Shum, J.S. Miller, J. Am. Chem. Soc. 124 (2002) 9336. Y. Nishida, S. Kida, Bull. Chem. Soc. Jpn. 45 (1972) 461. Synthesis of the Compound 1: The 10 mL aqueous solution of 57 mg (0.2 mmol) Mn(NO3)2 6H2O, 58 mg (0.2 mmol) Co(NO3)2 6H2O and 58 mg (0.2 mmol) Ni(NO3)2 6H2O was added dropwise into another 10 mL aqueous solution which contains 99 mg (0.2 mmol) H6TTHA and 48 mg (1.2 mmol) NaOH while stirring. Then the mixture was placed in an EtOH atmosphere without disturbance using the method of vapour diffusion. After a few weeks later, with the gaseous EtOH diffusing into the aqueous solution small light blue-violet single crystals suitable for X-ray analysis were formed (91 mg, 52% based on Mn). Elemental analysis of C18H48N4O24CoMnNi (877.18): calcd. C 24.65, H 5.52, N 6.39, Mn 6.26, Co 6.72, Ni 6.69; found C 24.76, H 5.43, N 6.07, Mn 6.66, Co 7.24, Ni 7.39. IR(KBr disk, cm1): 3250(b, mOH), 1580(b, mas(CO2)), 1325(m, ms(CO2)), 1100(m, mC–N). Absorption corrections were applied via an empirical correction (w scans; transmission factors varied from 0.59 to 0.76). The structure was solved by direct methods using the program SHELXS97 and refined on F2 by full matrix least-squares procedures using the program SHELXL97 and the residual factors R1 and wR2 is 0.0625, 0.1693, respectively. The non-hydrogen atoms were refined anisotropically and the hydrogen atoms were allowed to ride over their parent atoms. The hydrogen atoms on the water molecules could not be located. According to the elemental analysis data the proportional of Co:Ni is 1:1. The possibility that both the Co and the Ni positions are mixed Co/Ni sites cannot be excluded.