Diaqua­bis(picolinato N-oxide-κ²O,O′)zinc(II)

In the title compound, [Zn(C₆H₄NO₃)₂(H₂O)₂], the Zn atom is located on a centre of inversion and shows a distorted octa­hedral coordination geometry. Two aqua ligands occupy the axial positions and four O atoms of the two chelating picolinic acid N-oxide ligands are located in the equatorial plane. Inter­molecular hydrogen bonds between aqua ligands and organic ligands link mol­ecules into a two-dimensional arrangement.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.046
• wR factor = 0.149
• Data-to-parameter ratio = 11.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Zn1    -   O1W     ..       5.93 su
PLAT341_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          7
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2

Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for Zn1         (2)       2.16

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 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
   1 ALERT type 5 Informative message, check

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S1. Comment

In the past decade, much attention has been paid to the design and synthesis of self-assembling systems with organic ligands containing N and O donors (Bayot et al., 2006; Ciurtin et al., 2003; Steiner, 2002; Zafar et al., 2000). Picolinic acid N-oxide (PANO) is one such ligand and several crystal structures of complexes containing the PANO ligand have been reported (Yang et al., 2004; Shan et al., 2002; Lawrence et al., 1999; Meinrath et al., 2006). We report here the synthesis and crystal structure of the title complex, (I) (Fig. 1). In (I), the Zn atom is located on a crystallographic inversion centre and adopts a distorted octahedral coordination geometry. The coordination environment is defined by two pyridine N-oxide oxygen donors and two oxygen donors from the carboxylate groups located in the equatorial plane and two aqua O-atom donors located in the axial positions (Fig. 1). Selected bond lengths and angles are shown in Table 1. Intermolecular O1W—H1WA···O1, O1W—H1WB···O1 hydrogen bonds between water molecules and carboxylate groups connect the molecules of (I) into a two-dimensional network (Table 2 and Fig. 2).

Related literature

For related literature, see: Bayot et al. (2006); Ciurtin et al. (2003); Lawrence et al. (1999); Meinrath et al. (2006); Shan et al. (2002); Steiner (2002); Yang et al. (2004); Zafar et al. (2000).

S2. Experimental

All chemicals were obtained from commercial sources and used without further purification. The title compound was prepared by the direct reaction of Zn(OOCCH₃)₂.2H₂O (22.1 mg, 0.1 mmol) and picolinic acid N-oxide (13.9 mg, 0.1 mmol) in water solution. Colourless block-shaped single crystals were obtained by slow evaporation at room temperature for about three weeks.

S3. Refinement

Positional parameters of all H atoms were calculated geometrically and were allowed to ride on the C atoms to which they are bonded, with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 1999).

Figures

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Symmetry operation (A): [1 - x, 1 - y, 1 - z].
	Fig. 2. A packing diagram of (I). Hydrogen bonds are shown as dashed lines.

Diaquabis(picolinato N-oxide-κ²O,O')zinc(II)

Crystal data

[Zn(C6H4NO3)2(H2O)2]	F(000) = 384
Mr = 377.63	Dx = 1.887 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 6.6837 (5) Å	θ = 7.5–15°
b = 15.7376 (13) Å	µ = 1.90 mm^−1
c = 6.9935 (6) Å	T = 298 K
β = 115.370 (1)°	Block, colourless
V = 664.67 (9) Å^3	0.21 × 0.18 × 0.16 mm
Z = 2

Data collection

Bruker SMART CCD diffractometer	1170 independent reflections
Radiation source: fine-focus sealed tube	1033 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
Detector resolution: 10 pixels mm^-1	θmax = 25.0°, θmin = 2.6°
φ and ω scans	h = −7→7
Absorption correction: multi-scan CrystalClear (Rigaku, 2005)	k = −18→17
Tmin = 0.674, Tmax = 0.733	l = −6→8
3515 measured reflections

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)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.149	H-atom parameters constrained
S = 1.15	w = 1/[σ^2(Fo^2) + (0.0918P)^2 + 1.2258P] where P = (Fo^2 + 2Fc^2)/3
1170 reflections	(Δ/σ)max < 0.001
106 parameters	Δρmax = 0.56 e Å^−3
0 restraints	Δρmin = −0.90 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
Zn1	0.5000	0.5000	0.5000	0.0252 (3)
O1W	0.4917 (5)	0.43468 (18)	0.7653 (4)	0.0222 (7)
H1WA	0.6291	0.4170	0.8515	0.033*
H1WB	0.4423	0.4702	0.8365	0.033*
O1	−0.1745 (5)	0.49427 (16)	0.1316 (6)	0.0229 (7)
O2	0.1644 (5)	0.52224 (19)	0.3760 (5)	0.0218 (7)
O3	0.4215 (4)	0.38945 (17)	0.3288 (5)	0.0217 (7)
N1	0.2521 (5)	0.3424 (2)	0.3225 (5)	0.0168 (7)
C1	0.0530 (6)	0.3771 (2)	0.2833 (6)	0.0175 (8)
C2	−0.1198 (7)	0.3240 (3)	0.2650 (7)	0.0232 (9)
H2A	−0.2610	0.3483	0.2384	0.028*
C3	−0.0923 (8)	0.2365 (3)	0.2826 (7)	0.0287 (10)
H3A	−0.2135	0.1999	0.2667	0.034*
C4	0.1137 (8)	0.2034 (3)	0.3249 (7)	0.0273 (10)
H4A	0.1386	0.1432	0.3403	0.033*
C5	0.2825 (7)	0.2572 (3)	0.3436 (7)	0.0234 (9)
H5A	0.4259	0.2341	0.3737	0.028*
C6	0.0146 (6)	0.4725 (3)	0.2616 (6)	0.0177 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0186 (5)	0.0236 (5)	0.0293 (5)	−0.0011 (2)	0.0064 (4)	−0.0029 (3)
O1W	0.0178 (14)	0.0239 (15)	0.0222 (14)	0.0006 (11)	0.0059 (11)	0.0006 (11)
O1	0.0128 (16)	0.0208 (16)	0.0256 (17)	0.0033 (10)	−0.0008 (13)	−0.0021 (11)
O2	0.0118 (14)	0.0176 (13)	0.0289 (16)	−0.0007 (11)	0.0020 (12)	−0.0062 (13)
O3	0.0131 (13)	0.0210 (14)	0.0313 (16)	−0.0047 (11)	0.0099 (12)	−0.0094 (12)
N1	0.0162 (16)	0.0150 (16)	0.0172 (16)	−0.0009 (12)	0.0051 (13)	−0.0036 (13)
C1	0.0165 (19)	0.0163 (19)	0.0172 (19)	0.0014 (15)	0.0048 (16)	−0.0027 (15)
C2	0.019 (2)	0.021 (2)	0.028 (2)	−0.0020 (16)	0.0087 (18)	−0.0012 (17)
C3	0.032 (3)	0.023 (2)	0.032 (2)	−0.0086 (18)	0.015 (2)	−0.0015 (18)
C4	0.039 (3)	0.014 (2)	0.029 (2)	0.0003 (17)	0.014 (2)	−0.0004 (17)
C5	0.027 (2)	0.0164 (19)	0.025 (2)	0.0044 (16)	0.0089 (19)	−0.0026 (16)
C6	0.0146 (19)	0.0186 (19)	0.022 (2)	0.0019 (16)	0.0101 (16)	0.0006 (16)

Geometric parameters (Å, º)

Zn1—O3^i	2.049 (3)	N1—C1	1.354 (5)
Zn1—O3	2.049 (3)	N1—C5	1.356 (5)
Zn1—O2^i	2.059 (3)	C1—C2	1.386 (6)
Zn1—O2	2.059 (3)	C1—C6	1.520 (5)
Zn1—O1W^i	2.143 (3)	C2—C3	1.389 (6)
Zn1—O1W	2.143 (3)	C2—H2A	0.9600
O1W—H1WA	0.9000	C3—C4	1.381 (7)
O1W—H1WB	0.9001	C3—H3A	0.9601
O1—C6	1.247 (5)	C4—C5	1.371 (6)
O2—C6	1.253 (5)	C4—H4A	0.9597
O3—N1	1.338 (4)	C5—H5A	0.9600
O3^i—Zn1—O3	180.00 (8)	O3—N1—C5	117.3 (3)
O3^i—Zn1—O2^i	86.46 (11)	C1—N1—C5	120.6 (3)
O3—Zn1—O2^i	93.54 (11)	N1—C1—C2	118.9 (4)
O3^i—Zn1—O2	93.54 (11)	N1—C1—C6	121.8 (3)
O3—Zn1—O2	86.46 (11)	C2—C1—C6	119.2 (3)
O2^i—Zn1—O2	180.0	C3—C2—C1	121.1 (4)
O3^i—Zn1—O1W^i	90.21 (11)	C3—C2—H2A	119.6
O3—Zn1—O1W^i	89.79 (11)	C1—C2—H2A	119.3
O2^i—Zn1—O1W^i	91.07 (12)	C2—C3—C4	118.3 (4)
O2—Zn1—O1W^i	88.93 (12)	C2—C3—H3A	120.8
O3^i—Zn1—O1W	89.79 (11)	C4—C3—H3A	120.9
O3—Zn1—O1W	90.21 (11)	C5—C4—C3	119.5 (4)
O2^i—Zn1—O1W	88.93 (12)	C5—C4—H4A	120.2
O2—Zn1—O1W	91.07 (12)	C3—C4—H4A	120.3
O1W^i—Zn1—O1W	180.00 (13)	N1—C5—C4	121.5 (4)
Zn1—O1W—H1WA	109.3	N1—C5—H5A	119.2
Zn1—O1W—H1WB	109.5	C4—C5—H5A	119.4
H1WA—O1W—H1WB	109.5	O2—C6—O1	125.2 (4)
C6—O2—Zn1	126.3 (3)	O2—C6—C1	119.9 (4)
N1—O3—Zn1	119.4 (2)	O1—C6—C1	114.8 (3)
O3—N1—C1	121.9 (3)
O3^i—Zn1—O2—C6	−175.0 (3)	C2—C1—C2—C3	0 (100)
O3—Zn1—O2—C6	5.0 (3)	C6—C1—C2—C3	179.7 (4)
O1W^i—Zn1—O2—C6	94.8 (3)	C1—C2—C3—C2	0 (2)
O1W—Zn1—O2—C6	−85.2 (3)	C2—C2—C3—C4	0.0 (7)
O2^i—Zn1—O3—N1	137.7 (3)	C1—C2—C3—C4	1.8 (7)
O2—Zn1—O3—N1	−42.3 (3)	C2—C3—C4—C5	−1.4 (7)
O1W^i—Zn1—O3—N1	−131.2 (3)	C2—C3—C4—C5	−1.4 (7)
O1W—Zn1—O3—N1	48.8 (3)	O3—N1—C5—C4	−175.5 (4)
Zn1—O3—N1—C1	47.5 (4)	C1—N1—C5—C4	0.4 (6)
Zn1—O3—N1—C5	−136.6 (3)	C3—C4—C5—N1	0.3 (6)
O3—N1—C1—C2	175.7 (3)	Zn1—O2—C6—O1	−154.2 (3)
C5—N1—C1—C2	0.0 (6)	Zn1—O2—C6—C1	28.9 (5)
O3—N1—C1—C2	175.7 (3)	N1—C1—C6—O2	−36.9 (6)
C5—N1—C1—C2	0.0 (6)	C2—C1—C6—O2	142.3 (4)
O3—N1—C1—C6	−5.1 (5)	C2—C1—C6—O2	142.3 (4)
C5—N1—C1—C6	179.2 (4)	N1—C1—C6—O1	145.9 (4)
N1—C1—C2—C2	0.0 (2)	C2—C1—C6—O1	−34.9 (5)
C6—C1—C2—C2	0.00 (6)	C2—C1—C6—O1	−34.9 (5)
N1—C1—C2—C3	−1.1 (6)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1WB···O1^ii	0.90	1.98	2.753 (4)	143
O1W—H1WA···O1^iii	0.90	2.20	2.742 (4)	118

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