Bis(2-pyridine­carboxylato N-oxide-κ²O,O′)­nickel(II)

In the title complex, [Ni(C₆H₄NO₃)₂] or [Ni(L)₂] (L = 2-pyridine­carboxylic acid N-oxide), the Ni atom occupies a crystallographic inversion center and is coordinated by four O atoms of two ligands L, giving a square-planar geometry. The O atom of the N-oxide is also engaged in a weak inter­action with symmetry-related complexes [2.58 (3) Å] to form long Ni—O—Ni bridges, which extend parallel to the a axis. The stacking of the square-planar complexes is further stabilized by a slipped π–π inter­action between the pyridine rings of adjacent mol­ecules with a centroid-to-centroid distance of 3.3900 (7) Å and an inter­planar distance of 3.099 (2) Å, resulting in an offset angle of 24°.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.020
• wR factor = 0.051
• Data-to-parameter ratio = 9.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.98
PLAT088_ALERT_3_C Poor Data / Parameter Ratio ....................       9.43
PLAT180_ALERT_3_C Check Cell Rounding: # of Values Ending with 0 =          3
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Ni1    -   O2      ..       7.49 su
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Ni1    -   O3      ..       8.69 su
PLAT432_ALERT_2_C Short Inter X...Y Contact  O6     ..  C4      ..       3.01 Ang.
PLAT432_ALERT_2_C Short Inter X...Y Contact  C1     ..  C2      ..       3.11 Ang.
PLAT432_ALERT_2_C Short Inter X...Y Contact  C5     ..  C6      ..       3.12 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   8 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   5 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Metalcarboxylates with a high stability are efficient catalysts in a vast range of chemical and biochemical processes (Blay et al., 2001; Lassahn et al., 2004). Although a great number of metal carboxylate have been obtained to date, the rational design and synthesis of novel metal carboxylates by empolying new synthetic tools or by varying the natures of the reactants and synthetic conditions are currently under active investigation (Liu & Xu, 2005) In this context, 2-pyridine carboxylic acid N-oxide, which can exhibit a variety of coordination abilities and has a tendency to form architectures with multi-dimensional frameworks. In this paper, we report the synthesis and crystal structure of the title complex,(I).

In the title complex(I), [Ni(C₁₂H₈N₂O₆)₂] or [Ni(L)₂] (L=2-pyridine carboxylic acid N-oxide), the Ni atom occupies a crystallographic inversion center and is coordinated by four oxygen atoms from the carboxylate groups of the ligand L, giving a square planar geometry (Fig. 1). The square planar geometry is very similar to the previously reported structure in which the apical position were occupied by water molecules (at 2.09Å from the Ni) (Knuuttila, 1982).

The oxygen of the N-oxide is also engaged in a weak interaction with symmetry related molecules to form long Ni—O—Ni bridges which extend parallel to the a axis (Fig. 2). The stacking of the square planar complexes is further stabilized by slippest π-π interaction between the pyridine rings of adjacent molecules with a centroid-to-centroid distance of 3.3900 (7)Å and an interplanar distance of 3.099 (2)Å resulting in an offset angle of 24° (Fig. 2).

Related literature

For related literature, see: Blay et al. (2001); Knuuttila (1982); Lassahn et al. (2004); Liu & Xu (2005).

S2. Experimental

L(0.026 g, 0.013 mmol), NiCl2 (0.16 g, 0.11 mmol) and NaOH(0.048 mmol,0.12 mmol), were added in a mixed solvent of ethanol, the mixture was heated for three hours under reflux. during the process stirring and influx were required. The resultant was then filtered to give a pure solution which was infiltrated by diethyl ether freely in a closed vessel, a weeks later some single crystals of the size suitable for X-Ray diffraction analysis.

S3. Refinement

All H atoms were placed in calculated positions and treated as riding on their parent C atoms with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Version 1.4; Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. Molecular view of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented as smal spheres of arbitrary radii.[Symmetry code (i): -x + 1, -y + 1, -z + 1]
	Fig. 2. Partial packing view showing the stacking of the complexes throuth formation of elongated Ni—O—Ni bridges and slippest π-π interaction.

Bis(N-oxido-2-pyridinecarboxylato-κ²O,O')nickel(II)

Crystal data

[Ni(C6H4NO3)2]	F(000) = 340
Mr = 334.91	Dx = 2.147 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 915 reflections
a = 3.3900 (7) Å	θ = 2.3–25.2°
b = 12.590 (3) Å	µ = 1.91 mm^−1
c = 12.170 (2) Å	T = 298 K
β = 94.18 (3)°	Block, colourless
V = 518.04 (18) Å^3	0.29 × 0.21 × 0.18 mm
Z = 2

Data collection

Bruker APEXII area-detector diffractometer	915 independent reflections
Radiation source: fine-focus sealed tube	839 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
ϕ and ω scan	θmax = 25.2°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	h = −4→4
Tmin = 0.607, Tmax = 0.725	k = −14→15
3157 measured reflections	l = −14→14

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.020	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.051	H-atom parameters constrained
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0295P)^2 + 0.1009P] where P = (Fo^2 + 2Fc^2)/3
915 reflections	(Δ/σ)max < 0.001
97 parameters	Δρmax = 0.17 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ni1	0.5000	0.5000	0.5000	0.02274 (13)
O2	0.8684 (4)	0.39064 (10)	0.52462 (10)	0.0332 (3)
O3	0.4295 (4)	0.46542 (10)	0.34855 (10)	0.0321 (3)
O6	0.5595 (4)	0.38865 (11)	0.19304 (10)	0.0363 (3)
N2	0.8894 (4)	0.30378 (11)	0.46114 (12)	0.0234 (3)
C1	0.8087 (5)	0.20531 (14)	0.29725 (15)	0.0303 (4)
H1	0.7196	0.2011	0.2233	0.036*
C2	0.9798 (6)	0.11894 (15)	0.34717 (18)	0.0354 (5)
H2	1.0072	0.0558	0.3089	0.042*
C3	1.1109 (5)	0.12780 (14)	0.45565 (17)	0.0334 (4)
H3	1.2339	0.0703	0.4918	0.040*
C4	1.0625 (5)	0.22033 (15)	0.51132 (14)	0.0276 (4)
H4	1.1517	0.2252	0.5853	0.033*
C5	0.7630 (5)	0.29947 (13)	0.35319 (14)	0.0239 (4)
C6	0.5738 (5)	0.39276 (13)	0.29371 (14)	0.0253 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0274 (2)	0.02038 (19)	0.01969 (18)	0.00616 (11)	−0.00324 (13)	−0.00257 (11)
O2	0.0392 (8)	0.0295 (7)	0.0294 (7)	0.0109 (6)	−0.0084 (5)	−0.0096 (5)
O3	0.0357 (7)	0.0339 (7)	0.0258 (6)	0.0108 (6)	−0.0044 (5)	−0.0034 (6)
O6	0.0428 (8)	0.0429 (8)	0.0226 (7)	0.0039 (6)	−0.0008 (6)	−0.0025 (6)
N2	0.0215 (7)	0.0223 (8)	0.0267 (7)	−0.0003 (6)	0.0029 (6)	−0.0027 (6)
C1	0.0239 (9)	0.0338 (10)	0.0335 (9)	−0.0038 (7)	0.0033 (7)	−0.0066 (8)
C2	0.0279 (10)	0.0267 (10)	0.0523 (12)	−0.0003 (7)	0.0074 (9)	−0.0095 (9)
C3	0.0250 (10)	0.0256 (10)	0.0499 (12)	0.0011 (7)	0.0050 (9)	0.0036 (8)
C4	0.0231 (9)	0.0286 (10)	0.0310 (9)	0.0024 (7)	0.0012 (7)	0.0051 (7)
C5	0.0198 (9)	0.0263 (9)	0.0258 (8)	−0.0045 (7)	0.0027 (7)	−0.0014 (7)
C6	0.0231 (9)	0.0265 (9)	0.0259 (9)	−0.0042 (7)	−0.0009 (7)	−0.0030 (7)

Geometric parameters (Å, º)

Ni1—O2	1.8684 (13)	C1—C2	1.355 (3)
Ni1—O2^i	1.8684 (13)	C1—C5	1.381 (2)
Ni1—O3	1.8920 (13)	C1—H1	0.9300
Ni1—O3^i	1.8920 (13)	C2—C3	1.367 (3)
O2—N2	1.3437 (18)	C2—H2	0.9300
O3—C6	1.253 (2)	C3—C4	1.364 (3)
O6—C6	1.224 (2)	C3—H3	0.9300
N2—C4	1.330 (2)	C4—H4	0.9300
N2—C5	1.353 (2)	C5—C6	1.499 (2)
O2—Ni1—O2^i	180.000 (1)	C1—C2—H2	121.1
O2—Ni1—O3	91.27 (6)	C3—C2—H2	121.1
O2^i—Ni1—O3	88.73 (6)	C4—C3—C2	120.49 (17)
O2—Ni1—O3^i	88.73 (6)	C4—C3—H3	119.8
O2^i—Ni1—O3^i	91.27 (6)	C2—C3—H3	119.8
O3—Ni1—O3^i	180.000 (1)	N2—C4—C3	120.78 (16)
N2—O2—Ni1	124.77 (10)	N2—C4—H4	119.6
C6—O3—Ni1	131.34 (12)	C3—C4—H4	119.6
C4—N2—O2	114.77 (14)	N2—C5—C1	118.30 (16)
C4—N2—C5	120.80 (15)	N2—C5—C6	122.10 (14)
O2—N2—C5	124.38 (14)	C1—C5—C6	119.59 (16)
C2—C1—C5	121.83 (18)	O6—C6—O3	125.15 (17)
C2—C1—H1	119.1	O6—C6—C5	115.76 (15)
C5—C1—H1	119.1	O3—C6—C5	119.01 (15)
C1—C2—C3	117.77 (18)

Symmetry code: (i) −x+1, −y+1, −z+1.