Diaqua­(2,2′-bipyridine-6,6′-dicarboxyl­ato)nickel(II)

In the title compound, [Ni(C₁₂H₆N₂O₄)(H₂O)₂], the Ni^II atom (site symmetry 2) displays a distorted cis-NiN₂O₄ octa­hedral coordination geometry with two N atoms and two O atoms of the tetra­dentate 2,2′-bipyridine-6,6′-dicarboxyl­ate ligand in the equatorial plane and two water mol­ecules in axial positions. The complete dianionic ligand is generated by crystallographic twofold symmetry. In the crystal, a two-dimensional supra­molecular structure parallel to (001) is formed through O—H...O hydrogen-bond inter­actions between the coordinated water mol­ecules and the O atoms of nearby carboxyl­ate groups.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.032
• wR factor = 0.082
• Data-to-parameter ratio = 12.5

checkCIF/PLATON results

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Alert level C
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.09
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C1     -   C2     ...       1.53 Ang.
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600          3

Alert level G
PLAT002_ALERT_2_G Number of Distance or Angle Restraints on AtSite          3
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          2

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   3 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   2 ALERT level G = General information/check it is not something unexpected

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 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

Pyridyl carboxylic acid is an important class of organic ligands and has been widely used in coordination chemistry. 2,2'-Bipyridine-6,6'-dicarboxylate ligand is coordinated woth transition metal (Duan et al., 2009; Knight et al., 2006 and Wang et al., 2009) and lanthanide metal ions (Bunzli et al., 2000 and Wang et al., 2010). Herein, we report crystal structure of a new nickel complex with 2,2'-bipyridine-6,6'-dicarboxylate ligand.

The atom-numbering scheme of (I) is shown in Fig. 1. The Ni^II atom displays a distorted octahedral coordination geometry with two N atoms and two O atoms of 2,2'-bipyridine-6,6'-dicarboxylate in equatorial plane and two water molecules in apical positions. A two-dimensional supramolecular structure is formed through hydrogen interactions between the oxygen atoms of coordination water molecules and the oxygen atoms of carboxylate groups [O3—H3A···O2ⁱ, 2.708 (3) Å, 176 (3) °, symmetric code i: (-x - 1/2, -y + 3/2, z); O3—H3B···O2ⁱⁱ, 2.772 (3) Å, 172 (3) °, symmetric code ii: (-x, y - 1/2, -z + 1/2)].

Related literature

For transition metal complexes with the title ligand, see: Knight et al. (2006); Duan et al. (2009); Wang et al. (2009). For lanthanide metal complexes with the title ligand, see: Bunzli et al. (2000); Wang et al. (2010).

S2. Experimental

The title compound was prepared by the reaction of Ni(NO₃)₂ with 2,2'-bipyridine-6,6'-dicarboxylic acid (H₂bpdc) in a water solution. Ni(NO₃)₂.6H₂O (0.2 mmol) and H₂bpdc (0.2 mmol) were dissolved in 25 ml deionized water and adjusted the pH to 7 with 0.05 mol L^-1 NaOH aqueous solution. After one week, green blocks were obtained. Elmental analysis for C₁₂H₁₀N₂NiO₆ calculated: C 42.78, H 2.99, N 8.32%; found: C 42.57, H 2.89, N 8.46%.

S3. Refinement

The water H atoms were located in a difference Fourier map and refined with restrained O—H bond lengths [0.85 (2) Å] and fixed isotropic displancement parameters (U_iso(H) = 1.2 U_eq(O)). The carbon H atoms were placed at calculated positions (C—H = 0.93–0.96 Å) and refined as riding model with U_iso(H) = 1.2 U_eq(carrier).

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); 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 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of (I), showing 30% probability displacement ellipsoids. Atoms labelled with the suffix A are at the symmetry position (-x + 1/2, -y + 3/2, z).
	Fig. 2. View of a two-dimensional supramolecular structure constructed through hydrogen bonding interactions in (I). Hydrogen atoms of carbon atoms have been omitted for clarity.

Diaqua(2,2'-bipyridine-6,6'-dicarboxylato)nickel(II)

Crystal data

[Ni(C12H6N2O4)(H2O)2]	F(000) = 688
Mr = 336.93	Dx = 1.808 Mg m^−3
Orthorhombic, Pccn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2ac	Cell parameters from 1650 reflections
a = 7.1056 (9) Å	θ = 3.2–25.2°
b = 11.3608 (15) Å	µ = 1.60 mm^−1
c = 15.3334 (19) Å	T = 296 K
V = 1237.8 (3) Å^3	Block, green
Z = 4	0.24 × 0.16 × 0.10 mm

Data collection

Bruker APEXII CCD diffractometer	1274 independent reflections
Radiation source: fine-focus sealed tube	1098 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.036
ϕ and ω scans	θmax = 26.4°, θmin = 2.7°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −8→8
Tmin = 0.766, Tmax = 0.857	k = −13→14
6269 measured reflections	l = −10→19

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)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.082	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0405P)^2 + 0.5888P] where P = (Fo^2 + 2Fc^2)/3
1274 reflections	(Δ/σ)max < 0.001
102 parameters	Δρmax = 0.48 e Å^−3
2 restraints	Δρmin = −0.23 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	0.2500	0.7500	0.16327 (3)	0.02540 (16)
N1	0.0931 (3)	0.80137 (16)	0.06211 (12)	0.0285 (4)
O1	0.0167 (2)	0.83346 (15)	0.22531 (11)	0.0360 (4)
O2	−0.2446 (2)	0.93408 (18)	0.19595 (16)	0.0517 (6)
C1	−0.1035 (3)	0.8756 (2)	0.17424 (18)	0.0348 (6)
C2	−0.0683 (4)	0.8569 (2)	0.07707 (17)	0.0332 (6)
C3	−0.1808 (4)	0.8936 (2)	0.0083 (2)	0.0464 (7)
H3	−0.2934	0.9332	0.0182	0.056*
C4	−0.1204 (5)	0.8695 (3)	−0.0750 (2)	0.0563 (9)
H4	−0.1951	0.8915	−0.1221	0.068*
C5	0.0486 (5)	0.8132 (2)	−0.09017 (18)	0.0506 (8)
H5	0.0894	0.7982	−0.1467	0.061*
C6	0.1564 (4)	0.7796 (2)	−0.01856 (16)	0.0348 (6)
O3	0.1216 (2)	0.58888 (16)	0.17647 (13)	0.0380 (5)
H3A	0.009 (3)	0.584 (3)	0.1803 (18)	0.046*
H3B	0.169 (4)	0.545 (2)	0.2135 (15)	0.046*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0254 (3)	0.0293 (3)	0.0215 (2)	0.00250 (16)	0.000	0.000
N1	0.0341 (11)	0.0256 (10)	0.0260 (11)	−0.0004 (9)	−0.0053 (9)	−0.0005 (8)
O1	0.0336 (9)	0.0402 (10)	0.0343 (10)	0.0040 (8)	0.0046 (8)	−0.0040 (8)
O2	0.0263 (10)	0.0466 (12)	0.0821 (15)	0.0055 (8)	−0.0004 (9)	−0.0232 (11)
C1	0.0248 (12)	0.0269 (12)	0.0526 (17)	−0.0047 (10)	0.0005 (12)	−0.0078 (11)
C2	0.0316 (13)	0.0217 (12)	0.0464 (16)	−0.0021 (10)	−0.0109 (11)	−0.0021 (10)
C3	0.0437 (15)	0.0291 (14)	0.067 (2)	−0.0016 (11)	−0.0276 (15)	0.0050 (13)
C4	0.073 (2)	0.0378 (16)	0.059 (2)	−0.0073 (15)	−0.0407 (18)	0.0134 (14)
C5	0.085 (2)	0.0380 (16)	0.0289 (15)	−0.0094 (16)	−0.0177 (15)	0.0061 (11)
C6	0.0530 (17)	0.0261 (12)	0.0252 (12)	−0.0045 (11)	−0.0073 (12)	0.0018 (9)
O3	0.0259 (9)	0.0364 (10)	0.0519 (12)	0.0001 (8)	0.0044 (9)	0.0117 (8)

Geometric parameters (Å, º)

Ni1—N1^i	1.9975 (19)	C2—C3	1.387 (4)
Ni1—N1	1.9975 (19)	C3—C4	1.375 (5)
Ni1—O3^i	2.0553 (18)	C3—H3	0.9300
Ni1—O3	2.0553 (18)	C4—C5	1.381 (5)
Ni1—O1^i	2.1335 (16)	C4—H4	0.9300
Ni1—O1	2.1335 (16)	C5—C6	1.392 (4)
N1—C2	1.329 (3)	C5—H5	0.9300
N1—C6	1.339 (3)	C6—C6^i	1.491 (5)
O1—C1	1.254 (3)	O3—H3A	0.806 (18)
O2—C1	1.247 (3)	O3—H3B	0.827 (17)
C1—C2	1.526 (4)
N1^i—Ni1—N1	78.11 (11)	O2—C1—C2	117.8 (2)
N1^i—Ni1—O3^i	95.10 (8)	O1—C1—C2	116.4 (2)
N1—Ni1—O3^i	93.67 (8)	N1—C2—C3	120.6 (3)
N1^i—Ni1—O3	93.67 (8)	N1—C2—C1	112.1 (2)
N1—Ni1—O3	95.10 (8)	C3—C2—C1	127.3 (3)
O3^i—Ni1—O3	168.70 (11)	C4—C3—C2	117.8 (3)
N1^i—Ni1—O1^i	77.45 (7)	C4—C3—H3	121.1
N1—Ni1—O1^i	155.48 (8)	C2—C3—H3	121.1
O3^i—Ni1—O1^i	90.40 (7)	C3—C4—C5	121.4 (3)
O3—Ni1—O1^i	84.56 (7)	C3—C4—H4	119.3
N1^i—Ni1—O1	155.48 (8)	C5—C4—H4	119.3
N1—Ni1—O1	77.45 (7)	C4—C5—C6	118.2 (3)
O3^i—Ni1—O1	84.56 (7)	C4—C5—H5	120.9
O3—Ni1—O1	90.40 (7)	C6—C5—H5	120.9
O1^i—Ni1—O1	127.04 (9)	N1—C6—C5	119.5 (3)
C2—N1—C6	122.5 (2)	N1—C6—C6^i	112.53 (14)
C2—N1—Ni1	119.11 (17)	C5—C6—C6^i	127.93 (19)
C6—N1—Ni1	118.41 (17)	Ni1—O3—H3A	121 (2)
C1—O1—Ni1	114.88 (15)	Ni1—O3—H3B	115 (2)
O2—C1—O1	125.7 (3)	H3A—O3—H3B	108 (3)
N1^i—Ni1—N1—C2	−178.6 (2)	Ni1—N1—C2—C3	−179.86 (17)
O3^i—Ni1—N1—C2	−84.19 (18)	C6—N1—C2—C1	−177.4 (2)
O3—Ni1—N1—C2	88.68 (18)	Ni1—N1—C2—C1	1.8 (3)
O1^i—Ni1—N1—C2	176.75 (16)	O2—C1—C2—N1	175.2 (2)
O1—Ni1—N1—C2	−0.59 (17)	O1—C1—C2—N1	−2.6 (3)
N1^i—Ni1—N1—C6	0.53 (13)	O2—C1—C2—C3	−3.1 (4)
O3^i—Ni1—N1—C6	94.98 (18)	O1—C1—C2—C3	179.2 (2)
O3—Ni1—N1—C6	−92.15 (18)	N1—C2—C3—C4	0.6 (4)
O1^i—Ni1—N1—C6	−4.1 (3)	C1—C2—C3—C4	178.7 (2)
O1—Ni1—N1—C6	178.57 (19)	C2—C3—C4—C5	−1.5 (4)
N1^i—Ni1—O1—C1	3.7 (3)	C3—C4—C5—C6	1.0 (4)
N1—Ni1—O1—C1	−0.96 (16)	C2—N1—C6—C5	−1.6 (4)
O3^i—Ni1—O1—C1	94.04 (17)	Ni1—N1—C6—C5	179.24 (19)
O3—Ni1—O1—C1	−96.09 (17)	C2—N1—C6—C6^i	177.8 (2)
O1^i—Ni1—O1—C1	−179.58 (17)	Ni1—N1—C6—C6^i	−1.4 (3)
Ni1—O1—C1—O2	−175.4 (2)	C4—C5—C6—N1	0.6 (4)
Ni1—O1—C1—C2	2.1 (3)	C4—C5—C6—C6^i	−178.7 (3)
C6—N1—C2—C3	1.0 (4)

Symmetry code: (i) −x+1/2, −y+3/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3A···O2^ii	0.81 (2)	1.90 (2)	2.708 (2)	176 (3)
O3—H3B···O2^iii	0.83 (2)	1.95 (2)	2.772 (3)	172 (3)

Symmetry codes: (ii) −x−1/2, −y+3/2, z; (iii) −x, y−1/2, −z+1/2.