Springer 2007
Transition Metal Chemistry (2007) 32:711–715 DOI 10.1007/s11243-007-0234-2
Synthesis, crystal structure and magnetic property of the novel dinuclear nickel(II) complex with 4-(p-methoxyphenyl)-3,5-bis(pyridine-2-yl)-1,2,4-triazole Jun Zhou, Jie Yang, Li Qi, Xuan Shen and Dunru Zhu* College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, P.R. China Yan Xu Institute of Chemistry for Functionalized Materials, College of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, P.R. China You Song State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, P.R. China Received 26 January 2007; accepted 08 March 2007
Abstract A novel dinuclear nickel(II) complex, [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O (MOBPT = 4-(p-methoxyphenyl) )3,5bis(pyridine-2-yl)-1,2,4-triazole), has been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction methods. The crystal structure determination shows that the dinuclear Ni2N8 unit is almost planer in which each NiII ion is coordinated by four nitrogen atoms from MOBPT equatorially and a water molecule and a chloride ion axially in a distorted octahedral geometry. Magnetic measurements reveal a relatively weak antiferromagnetic exchange in the complex.
Introduction Dinuclear transition metal complexes with 1,2,4-triazole ligands have attracted great and growing interest in the coordination chemistry because of an important interface between specific structures [1, 2], magnetic properties [3–6] and materials science [7, 8]. Compared with alkyl-substituted 1,2,4-triazole [9, 10], dinuclear complexes containing triaryltriazole ligand have been rarely studied so far [11–13]. Recently we have synthesized some triaryltriazole compounds [14–16], which could be acted as doubly-bidentate chelating ligands because of their structural similarity to 4-amino-3,5bis(pyridine-2-yl)-1,2,4-triazole (NH2BPT) [1]. This paper deals with the first dinuclear complex with one of the triaryltriazole ligands. We report the synthesis, crystal structure and magnetic property of a novel dinuclear nickel(II) complex with 4-(p-methoxyphenyl)3,5-bis(pyridine-2-yl)-1,2,4-triazole (MOBPT), [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O.
Experimental Materials and measurements All chemicals used were of analytical grade. Solvents were purified by conventional methods. The ligand * Author for correspondence: E-mail:
[email protected]
MOBPT was synthesized according to the literature method [17–19]. Elemental analysis was performed with a Perkin-Elmer 240 instrument. IR spectrum was recorded on a Nicolet Avatar 380 FT-IR instrument (KBr discs) in the 4,000–400 cm)1 region. Variable temperature magnetic susceptibilities of crystalline sample were measured on a Quantum Design MPMS SQUID-XL7 magnetometer. Diamagnetic corrections were made with Pascal’s constants for all the constituent atoms. Preparation of [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O To a colorless solution of MOBPT (197.62 mg, 0.6 mmol), in warm EtOH (15 cm3), was added dropwise a grass green solution of NiCl2 Æ 6H2O (142.62 mg, 0.6 mmol) in EtOH (5 cm3). The resulting green solution was stirred at room temperature for 6 h. The pale–green precipitate which formed was filtered, washed with a little H2O and acetone. Then the solid was re-dissolved in a solution of 95% EtOH. Evaporation of the solvent at room temperature for three weeks yielded a light-green crystal suitable for X-ray diffraction. Yield based on MOBPT: 210.6 mg, 65%. C38H48Cl4N10Ni2O11 (Found: C, 42.0; H, 4.3; N, 13.1%; calcd.: C, 42.3; H, 4.5; N, 13.0%). IR (KBr, cm)1): 3473-3021(s, b), 2942m, 1608s, 1513s, 1471s, 1439s, 1300m, 1260s, 1169m, 1029m, 843m, 794m, 750m, 716s, 644s, 625m.
712 Crystal structure determination
Results and discussion
A light-green block crystal of the complex, with dimensions 0.50 0.20 0.15 mm, was selected for lattice parameter determination and collection of intensity data at 293 K on a Bru¨ker P4 four-circle diffractometer with monochromated Mo Ka radiation (k = 0.71073 A˚) using a x scan mode. The data was corrected for Lorenz and polarization effects during data reduction. An empirical absorption correction based on w scans was applied. The structure was solved by the direct methods and refined on F2 by fullmatrix least-squares methods using SHELXTL version 5.10 [20]. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms for C–H and O–H were placed in calculated positions and allowed to ride on the parent atoms to which they are attached except O5w with an occupancy of 0.5. The contribution of these hydrogen atoms was included in the structure factor calculations. All computations were carried out using the SHELXTL program package. Analytical anomalous dispersion corrections were incorporated. The final R factor was 0.0603 {Rx = 0.1512 where x = 1/[r2(F02) + (0.0871P)2 + 0.8399P] and P = (F02 + 2FC2)/3} for 328 parameters, 2860 observed reflections [I > 2r(I)]. The maximum and minimum residual peaks in the final differences maps were 0.721 and ) 1.215 eA˚)3. Crystal data: C38H48Cl4N10Ni2O11, M=1080.08, triclinic, P1, a=10.329(2), b=10.522(3), c=11.9497(18) A˚, a=77.661(19), b=79.050(13), c=66.153(17), V=1152.6(4) A˚3, Z=1, Dcalcd=1.556 g cm)3; T=293 K, 4788 reflections collected, 4053 unique reflections (Rint=0.0381). The CIF has been deposited at the Cambridge Crystallographic Data Centre, CCDC reference number 627946. Copies of this information may be obtained free of charge via www.ccdc.cam.ac.uk (or from the Cambridge Crystallographic Centre, 12 Union Road, Cambridge CB21EZ, UK; Fax: +44-1223-336033; e-mail:
[email protected]).
The triaryltriazole ligand, MOBPT, reacts with NiCl2 Æ 6H2O in 1:1 molar ratio to form a neutral dinuclear complex, [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O, which is stable in air. The elemental analysis is satisfactory and indicates that the complex contains two nickel atoms, two MOBPT ligands, four chloride ions and nine water molecules. The MOBPT acts as doubly-bidentate chelating ligand for the first time in the complex [18, 19].
Crystal structure Single crystal X-ray analysis reveals that the complex contains a dinuclear cation as shown in Figure 1. The complex contains a [Ni2(MOBPT)2Cl2(H2O)2]2+ cation, two Cl) anions, and seven lattice water molecules. There is an inversion centre at the centre of the cation thereby making the two Ni atoms crystallographically equivalent in the solid state. The dinuclear [Ni2N8] unit in the cation is almost planar. The distance of the nickel atoms to the least-squares plane through the coordinating nitrogen atoms is 0.03 A˚. In this plane the dinuclear (N¢,N1,N2,N¢¢)2 double-bridging coordination mode is observed in the [Ni2(MOBPT)2Cl2(H2O)2]2+ cation by the two ligands. Each nickel atom is axially coordinated by a H2O molecule and a Cl) anion, resulting in a distorted octahedral coordination environment. The selected bond lengths and angles are given in Table 1. The Ni–Npyr bond lengths [2.159(4)–2.192(3) A˚] are quite longer than the Ni–Ntrz bond lengths [2.038(3)–2.044(3) A˚]. Both of them are somewhat larger than the corresponding bond lengths observed in [Ni2(NH2BPT)2Cl2(H2O)2]Cl2 Æ 4H2O [1] [2.155(1)–2.164(1) A˚; 2.013(1)–2.029(1) A˚, respectively], [Ni2(ibdpt)2(MeCN)4](ClO4)4 [6], [2.139(3)–2.149(3) A˚; 2.023(3)–2.031(3) A˚] and [Ni2(pldpt)2(MeCN)4](-BF4)4 Æ 2MeCN [13] [2.149(2)–2.184(2) A˚; 2.023(2)–2.042(2) A˚]. The Ni–O [2.096(3) A˚] and Ni–Cl [2.396(1) A˚] distances
Fig. 1. Projection of the [Ni2(MOBPT)2Cl2(H2O)2]2+ cation with the atomic labeling system. Hydrogen atoms are omitted for clarity.
713 Table 1. Selected bond distances (A˚) and angles () for the complexA Bond lengths Ni(1)–N(1)a Ni(1)–N(3) Ni(1)–Cl(1) N(1)–C(6) N(2)–C(7) N(1)–N(2) Ni–Nia Bond angles N(2)–Ni(1)–N(1)a N(2)–Ni(1)–N(3) O(1W)–Ni(1)–N(3) N(2)–Ni(1)–Cl(1) N(3)–Ni(1)–Cl(1) N(1)a–Ni(1)–N(3)
2.044(3) 2.192(3) 2.396(1) 1.312(5) 1.312(4) 1.355(4) 4.189(5) 92.06(12) 75.84(12) 87.07(12) 95.80(10) 86.37(10) 167.90(13)
Ni(1)–N(2) Ni(1)–N(4)a Ni(1)–O(1W) N(3)–C(8) N(4)–C(5) O(1)–C(13) O(1)–C(14) N(1)a–Ni(1)–N(4)a O(1W)–Ni(1)–N(2) O(1W)–Ni(1)–N(4)a N(4)a–Ni(1)–Cl(1) O(1W)–Ni(1)–Cl(1) N(2)–Ni(1)–N(4)a
2.038(3) 2.159(4) 2.096(3) 1.345(5) 1.360(4) 1.438(5) 1.366(5) 76.61(12) 93.28(13) 85.08(13) 87.79(10) 167.15(9) 168.40(11)
Symmetry code: a = 1 ) x, 2 ) y, 2 ) z.
A
are in the normal range as those observed in [Ni2(NH2BPT)2Cl2(H2O)2]Cl2 Æ 4H2O. The Ni–Ni distance in the present complex is 4.189(5) A˚, which is slightly larger than that found in the related dinuclear nickel(II) complexes: [Ni2(NH2BPT)2Cl2(H2O)2]Cl2 Æ 4H2O [4.1348(3) A˚], [Ni2(ibdpt)2(MeCN)4](ClO4)4 [4.1107(9) A˚] and [Ni2(pldpt)2(MeCN)4](BF4)4 Æ 2MeCN [4.170(1) A˚]. The pyridine–triazole–pyridine moiety of the ligand is nearly perfectly planar [2.2(2) and 3.4(2)] while the phenyl ring is inclined relative to the triazole ring by an angle of 77.9(4). The crystal structure is further stabilized by intramolecular and intermolecular hydrogen bonds (Figure 2). Both of hydrogen bonds consist of a usual OÆÆÆO contact and a weak OÆÆÆCl contact (Table 2). IR spectrum In the IR spectrum of [Ni2(MOBPT)2Cl2(H2O)2] Cl 2 Æ 7H2O, there are several broad, strong bands at ca. 3473, 3370, 3219, 3067 and 3021 cm)1, mainly attributed to H–O–H stretching vibrations, suggesting the existence of hydrogen bonding interactions [21]. This is in agreement with the X-ray analysis. The IR spectrum of the complex can also be closely related to that of
free MOBPT. One of the most diagnostic changes occurs between 1610 and 1560 cm)1. The free MOBPT spectrum shows a strong band at 1584.5 cm)1 and a medium band at 1567.3 cm)1, attributable to the pyridine ring vibrations. Upon pyridine coordination to a metal the higher band is shifted by ca. +15 wavenumbers. Thus in the spectrum of the complex, a band at 1,608 cm)1 (s) can be assigned to the coordinated pyridine ring [22]. This means that in this complex, MOBPT ligand uses two pyridine nitrogens and two triazole nitrogens for doubly-bidentate chelate binding ðN0 ; N1 , N2 , N¢¢), as was confirmed by the structure determination. In addition, two bands at 1260 (s) and 1029 cm)1 (m) are due to Ar–O–C asymmetry and symmetry stretching vibrations, respectively. The C–H out of plane absorption of the para-substituted phenyl is located around 843 (m) and 794 cm)1 (m). The triazoleout-of-plane ring absorption is observed at about 644 cm)1 (s). Magnetic property The variable-temperature magnetic susceptibility of the complex performed on a crystalline sample was investigated using a SQUID magnetometer in the temperature
Fig. 2. The unit-cell packing of [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O. Broken lines indicate hydrogen bonds.
714 Table 2. Hydrogen-bonding geometry (A˚, ) for the complexA Intramolecular
O(1W)ÆÆÆO(5W) O(2W)ÆÆÆO(5W) O(3W)ÆÆÆCl(2) O(1W)ÆÆÆCl(3) O(4W)ÆÆÆCl(1) O(2W)ÆÆÆCl(3) O(1W)ÆÆÆO(3W)a O(4W)ÆÆÆO(5W)b O(4W)ÆÆÆCl(3)b O(2W)ÆÆÆO(3W)a O(3W)ÆÆÆCl(1)c
Intermolecular
2.881(1) 2.864(1) 2.964(1) 3.082(1) 3.099(1) 3.236(1) 2.698(1) 2.987(1) 3.159(1) 2.860(1) 3.163(1)
O(1W)–H(1WA)ÆÆÆO(5W) O(2W)–H(2WB)ÆÆÆO(5W) O(3W)–H(3WB)ÆÆÆCl(2) O(1W)–H(1WA)ÆÆÆCl(3) O(4W)–H(4WB)ÆÆÆCl(1) O(2W)–H(2WB)ÆÆÆCl(3) O(1W)–H(1WB)ÆÆÆO(3W)a O(4W)–H(4WA)ÆÆÆO(5W)b O(4W)–H(4WA)ÆÆÆCl(3)b O(2W)–H(2WA)ÆÆÆO(3W)a O(3W)-H(3WA)ÆÆÆCl(1)c
163.1(1) 167.5(1) 150.0(1) 171.0(1) 124.0(1) 167.9(1) 173.5(1) 169.6(1) 171.8(1) 135.6(1) 145.8(1)
Symmetry code: a = x + 1, y, z; b = 1 ) x, 2 ) y, 2 ) z; c = ) x, 2 ) y, 2 ) z.
A
range 300–1.8 K within an applied field of 2000 Oe. The magnetic behavior of the complex is shown in Figure 3 in the form of a vM versus T plot. The temperature dependence of the vM data reveals the existence of antiferromagnetic coupling between the NiII metal sites joined via the l -N1,N2 triazole ligand. The vM value at 300 K is 0.0073 emu Æ mol)1, which is about the value expected for a pair of uncoupled octahedrally coordinated Ni(II) ions with a 3A2 ground state. As the temperature is reduced, vM value gradually increases to reach the maximum of 0.0394 emu Æ mol)1 at 26 K and then decreases to 0.0036 emu Æ mol)1 at 1.8 K. The magnetic data can be fitted extremely well to an S = 1 Heisenberg dimer 2JS1 S2 model, Equation (1) [23], where N is Avogadro’s number, k is the B.M, and b is the Boltzmann constant, g, J and zJ¢ are adjustable parameters. The best least squares fit parameters gave g = 2.16, J = ) 8.43(6) cm)1, zJ0 ¼ 0:8ð1Þ cm1 . The coupling constant is similar to the corresponding value observed for [Ni2(pldpt)2])(ClO4)4 and [Ni2(pldpt)2(H2O)4](BF4)4 [13] and less than that observed in related nickel(II) complexes of other 4-substituted 3,5bis(pyridine-2-yl)-1,2,4-triazole [1, 6] (Table 3). vM ¼
vd 1 ð2zj0 =Ng2 b2 Þvd
vd ¼
ð1Þ
2Ng2 b2 e2J=kT þ 5e6J=kT kT 1 þ 3e2J=kT þ 5e6J=kT
-1
2.0
3.0
χM
2.5
1.5
χMT
2.0 1.0
1.5
0.5
-1
1.0
χMT / emu K mol
-2
J (cm)1)
g
References
[Ni2(NH2BPT)2Cl2(H2O)2]Cl2 Æ 4H2O [Ni2(NH2BPT)2(H2O)4](BF4)4 [Ni2(ibdpt)2(MeCN)](ClO4)4 [Ni2(pldpt)2](ClO4)4 [Ni2(pldpt)2(H2O)4](BF4)4 [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O
) 12.5 ) 9.0 ) 13.0 ) 8.8 ) 7.8 ) 8.43
2.15 2.25 2.08 2.05 2.15 2.16
[1] [1] [6] [13] [13] this work
Conclusion In summary, a novel dinuclear nickel(II) complex, [Ni2(MOBPT)2Cl2(H2O)2]Cl2 Æ 7H2O, has been synthesized and structurally characterized by single-crystal X-ray diffraction. The complex exhibits a weak antiferromagnetic exchange coupling between two NiII centers mediated by two central triazole bridges of MOBPT ligand.
This work was funded by the Natural Science Foundation of the Department of Education of Jiangsu Province (05KJB150045) and the Open Foundation of the State Key Laboratory of Coordination Chemistry, Nanjing University.
2.5
3.5 χM / (10 ) emu mol
Complex
Acknowledgements
4.0
0.5 0.0 -0.5
Table 3. Main magnetic parameters for the dinuclear nickel(II) complexes with 4-substituted 3,5-bis(pyridine-2-yl)-1,2,4-triazole
0.0 0
50
100
150 T/K
200
250
300
Fig. 3. vM(h) vs. T and vMT(s) vs. T plot for [Ni2(MOBPT)2Cl2 (H2O)2]Cl2 Æ 7H2O.
References 1. F.S. Keij, R.A.G. de Graaff, J.G. Haasnoot and J. Reedijk, J. Chem. Soc. Dalton Trans., 2093 (1984). 2. P.J. van Koningsbruggen, D. Gatteschi, R.A.G. de Graaff, J.G. Haasnoot, J. Reedijk and C. Zanchini, Inorg. Chem., 34, 5175 (1995). 3. R. Prins, P.J.M.L. Birker, J.G. Haasnoot, G.C. Verschoor and J. Reedijk, Inorg. Chem., 24, 4128 (1985). 4. W.M.E. Koomen-van Oudennie, R.A.G. de Graaff, J.G. Haasnoot, R. Prins and J. Reedijk, Inorg. Chem., 28, 1128 (1989). 5. M.H. Klingele, B. Moubaraki, K.S. Murray and S. Brooker, Chem. Eur. J., 11, 6962 (2005). 6. M.H. Klingele, P.D.W. Boyd, B. Moubaraki, K.S. Murray and S. Brooker, Eur. J. Inorg. Chem., 910 (2005).
715 7. J.J.A. Kolnaar, M.I. de Heer, H. Kooijman, A.L. Spek, G. Schmitt, V. Ksenofontov, P. Gutlich, J.G. Haasnoot and J. Reedijk, Eur. J. Inorg. Chem., 881 (1999). 8. M.H. Klingele, B. Moubaraki, J.D. Cashion, K.S. Murray and S. Brooker, Chem. Commun., 987 (2005). 9. J.G. Haasnoot, Coord. Chem. Rev., 200–202, 131 (2000). 10. M.H. Klingele and S. Brooker, Coord. Chem. Rev., 241, 119 (2003). 11. S.K. Mandal, H.J. Clase, J.N. Bridson and S. Ray, Inorg. Chim. Acta, 209, 1 (1993). 12. S.-C. Shao, Z.-L. You, S.-P. Zhang, H.-L. Zhu and S.W. Ng, Acta Crystallogr., E61, m265 (2005). 13. M.H. Klingele, P.D.W. Boyd, B. Moubaraki, K.S. Murray and S. Brooker, Eur. J. Inorg. Chem., 573 (2006). 14. D.-R. Zhu, PhD Thesis, Nanjing University, P.R. China, (2000). 15. D. Zhu, Y. Xu, Z. Yu, Z. Guo, H. Sang, T. Liu and X. You, Chem. Mater., 14, 838 (2002). 16. D.-R. Zhu, Z.-X. Wang, J. Song, Y.-Z. Li and D.-Y. Lan, Chin. J. Inorg. Chem., 21, 128 (2005).
17. H.-K. Fun, K. Chinnakali, S. Shao, D. Zhu and X.Z. You, Acta Crystallogr., C55, 770 (1999). 18. D. Zhu, Y. Song, Y. Liu, Y. Xu, Y. Zhang and X. You, Transition Met. Chem., 25, 589 (2000). 19. D. Zhu, Y. Xu, Y. Mei, Y. Shi, C. Tu and X. You, J. Mol. Struct., 559, 119 (2001). 20. G.M. Sheldrick, SHELXTL, Structure Determination Software Programs. Version 5.10., Bruker Analytical X-ray Systems Inc, Wisconsin, USA, 1997. 21. K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, Wiley, New York, 1970, p. 166. 22. U. Hartmann and H. Vahrenkamp, Inorg. Chim. Acta, 239, 13 (1995). 23. A.P. Ginsberg, R.L. Martin, R.W. Brookes and R.C. Sherwood, Inorg. Chem., 11, 2884 (1972).
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