Bis{tris­[3-(2-pyrid­yl)-1H-pyrazole]nickel(II)} dodeca­molybdo(V,VI)phosphate hexa­hydrate

Lujiang Hao; Tongjun Liu; Jiangkui Chen; Xiaofei Zhang

doi:10.1107/S1600536810005945

. 2010 Feb 20;66(Pt 3):m319–m320. doi: 10.1107/S1600536810005945

Bis{tris[3-(2-pyridyl)-1H-pyrazole]nickel(II)} dodecamolybdo(V,VI)phosphate hexahydrate

Lujiang Hao ^a,^*, Tongjun Liu ^a, Jiangkui Chen ^a, Xiaofei Zhang ^a

PMCID: PMC2983742 PMID: 21580258

Abstract

The hydrothermally prepared title compound, [Ni(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O, is a member of the isotypic series [(M(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O where M is Mn, Cd, and Fe. The Ni²⁺ cation is in a distorted octahedral environment, coordinated by six N atoms from three chelating 3-(2-pyridyl)-1H-pyrazole ligands. In the one-electron reduced heteropolyanion, two O atoms of the central PO₄ group ( Inline graphic symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonds contribute to the crystal packing. Compared with the isotypic structures, the main difference is related with the M—N bond lengths, whereas all other bond lengths, angles and the hydrogen-bonding motifs are very similar.

Related literature

For the isotypic analogues, see: Hao, Ma et al. (2010 ▶) for M = Mn; Hao, Wang et al. (2010 ▶) for M = Cd; Hao, Liu, et al. (2010 ▶) for M = Fe. For general background to polyoxometalates, see: Pope & Müller (1991 ▶). For polyoxometalates modified with amines, see: Zhang, Dou et al. (2009 ▶); Zhang, Wei et al. (2009 ▶). For the structures of other reduced heteropolyanions with composition [PMo₁₂O₄₀]⁴⁻, see: Artero & Proust (2000 ▶); Kurmoo et al. (1998 ▶).; Niu et al. (1999 ▶). For the role of amines in hydrothermal synthesis, see: Yang et al. (2003 ▶).

Experimental

Crystal data

[Ni(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O
M _r = 2918.76
Monoclinic,
a = 18.741 (4) Å
b = 16.285 (3) Å
c = 27.678 (6) Å
β = 103.83 (3)°
V = 8202 (3) Å³
Z = 4
Mo Kα radiation
μ = 2.34 mm⁻¹
T = 293 K
0.42 × 0.27 × 0.20 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2001 ▶) T _min = 0.440, T _max = 0.652
22802 measured reflections
7216 independent reflections
5310 reflections with I > 2σ(I)
R _int = 0.062

Refinement

R[F ² > 2σ(F ²)] = 0.053
wR(F ²) = 0.155
S = 1.00
7216 reflections
592 parameters
18 restraints
H-atom parameters constrained
Δρ_max = 1.58 e Å⁻³
Δρ_min = −0.67 e Å⁻³

Data collection: APEX2 (Bruker, 2004 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810005945/wm2306sup1.cif

e-66-0m319-sup1.cif^{(34.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810005945/wm2306Isup2.hkl

e-66-0m319-Isup2.hkl^{(353.2KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Ni1—N5	2.077 (19)
Ni1—N8	2.06 (2)
Ni1—N2	2.084 (19)
Ni1—N4	2.13 (2)
Ni1—N1	2.118 (17)
Ni1—N7	2.14 (2)
P1—O21Aⁱ	1.49 (2)
P1—O21Bⁱ	1.50 (3)
P1—O19Bⁱ	1.55 (3)
P1—O19Aⁱ	1.57 (3)

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Symmetry code: (i) Inline graphic .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3A⋯O17ⁱⁱ	0.86	2.05	2.83 (3)	149
N6—H6⋯O2W	0.86	1.99	2.84 (5)	166
N9—H9A⋯O1W	0.86	1.92	2.74 (3)	160

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Symmetry code: (ii) Inline graphic .

Acknowledgments

Financial support from the International Cooperation Program for Excellent Lecturers of 2008 from Shandong Provincial Education Department, the Research Award Fund for Outstanding Young and Middle-aged Scientists of Shandong Province (2008BS04022), Shandong Provincial Education Department and Shandong Institute of Education are gratefully acknowledged.

supplementary crystallographic information

Comment

The design and synthesis of polyoxometalates has attracted continuous research interest not only because of their appealing structural and topological novelties, but also due to their interesting optical, electronic, magnetic, and catalytic properties, as well as their potential medical applications (Pope & Müller, 1991). In our research group, organic amines, such as 3-(2-pyridyl)pyrazole and pyrazine, are used to effectively modify polyoxomolybdates under hydrothermal condictions (Zhang, Dou et al., 2009; Zhang, Wei et al., 2009). Here, we describe the synthesis and structural characterization of the title compound.

As shown in Figure 1, the asymmetric unit of the title compound consists of three subunits, viz. of a complex [Ni(C₈H₇N₃)₃]²⁺ cation, half of a heteropolyanion [PMo₁₂O₄₀]^4- and of three uncoordinated water molecules. The nickel(II) ion is in a distorted octahedral coordination by six N atoms from three chelating 3-(2-pyridyl)-1H-pyrazole ligands.

The heteropolyanion [PMo₁₂O₄₀]^4- anion is a one-electron reduced derivative of [PMo₁₂O₄₀]^3-, similar to anions with different counter cations as reported by Artero & Proust (2000); Kurmoo et al. (1998); Niu et al. (1999). The employed organic ligand appears to adjust the pH value, and additionally supplies reducing electrons, which is a commonly observed feature of hydrothermal syntheses when organic amines are used to prepare various hybrid materials, zeolites or metal phosphates (Yang et al., 2003).

In the Keggin-type heteropolyanion, each Mo atom is surrounded by six O atoms and the P atom is located at the center of the anion. There are four kinds of O atoms present in the anion according to their coordination environments: O_a (O atoms in the disordered PO₄ tetrahedron), O_b (bridging O atoms between two triplet groups of MoO₆ octahedra), O_c (bridging O atoms within one triplet group of MoO₆ octahedra) and O_d (terminal O atoms). The P—O bond distances are in the normal range of 1.49 (2)—1.57 (3) Å. The Mo—O bond distances vary widely from 1.653 (15) to 2.55 (2) Å. The shortest Mo—O bonds are in the range of 1.653 (15)—1.665 (16) Å for the terminal oxygen atoms. The longest Mo—O lengths are in the range of 2.44 (2)—2.55 (2) Å for those oxygen atoms connected with both Mo and P atoms.

N—H···O and O—H···O hydrogen bonding between the cationic and anionic moieties and the uncoordinated water molecules leads to a consolidation of the structure (Fig. 2; Table 2).

The crystal structure of [(Ni(C₈H₇N₃)₃]₂[PMo₁₂O₄₀](H₂O)₆ is isotypic with the Mn²⁺, Cd²⁺, and Fe²⁺ analogues, [(Mn(C₈H₇N₃)₃]₂[PMo₁₂O₄₀](H₂O)₆ (Hao, Ma et al. (2010).), [(Cd(C₈H₇N₃)₃]₂[PMo₁₂O₄₀](H₂O)₆ (Hao, Wang et al. (2010).), [(Fe(C₈H₇N₃)₃]₂[PMo₁₂O₄₀](H₂O)₆ (Hao, Liu et al., 2010). In comparison with the Mn²⁺, Cd²⁺, and Fe²⁺ analogues, the Ni—N bond lengths are somewhat shorter at 2.077 (19)—2.14 (2) Å, versus 2.224 (6)—2.283 (5) Å for Mn—N, 2.085 (19)—2.15 (2) Å for Fe—N, and 2.316 (7)—2.334 (6) Å for Cd—N, whereas all other bond lengths and angles and the hydrogen-bonding motifs are very similar in the four structures.

Experimental

A mixture of 3-(2-pyridyl)-1H-pyrazole (0.5 mmoL 0.07 g), sodium molybdate (0.4 mmoL, 0.10 g), nickel(II) chloride hexahydrate (0.25 mmol, 0.05 g), and dipotassium hydrogenphosphate (0.22 mmol, 0.05 g) in 10 ml distilled water was sealed in a 25 ml Teflon-lined stainless steel autoclave and was kept at 433 K for three days. Green crystals suitable for the X-ray experiment were obtained. IR(cm^-1): 3376, 3136, 2961, 1614, 1568, 1522, 1457, 1439, 1364, 1300, 1097, 950, 913, 812, 636, 507.

TGA curve shows a separation of lattice water molecules and the organic ligands above 343 and 682 K, respectively. The overall thermal decomposition process can be described by the followed equation: 4C₄₈H₅₄Ni₂Mo₁₂N₁₈O₄₆P + 325O₂ = 108H₂O + 192CO₂ + 36N₂O₅ + 8NiO + 2P₂O₅ + 48MoO₃