Diaqua­bis(2-pyridylphospho­nato N-oxide-κ²O¹,O²)cobalt(II)

In the title complex, [Co(C₅H₅NO₄P)₂(H₂O)₂], the Co^II ion, which lies on a crystallographic inversion center, is coordin­ated by four O atoms from two bidentate 2-phospho­nato­pyridine N-oxide ligands and two O atoms from two water ligands in a slightly distorted octa­hedral environment. Mol­ecules are inter­linked by three O—H...O hydrogen bonds and one weak C—H...O inter­action, forming a three-dimensional supra­molecular structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.051
• wR factor = 0.109
• Data-to-parameter ratio = 14.6

checkCIF/PLATON results

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Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT720_ALERT_4_G Number of Unusual/Non-Standard Labels ..........          2

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
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S1. Comment

The chemistry of metal phosphonates has received an increasing attention in recent years for their new architectures and properties in catalysis, ion exchange and magnetic materials (Cao et al., 1992). It has been well known that the monophosphonic acid RPO₃H₂, where R represents an alkyl or aryl group, prefer to form layered structures with transition metal ions (Clearfield 1998). There are some metal phosphonates reported during the past several years which contain pyridyl groups (Ayyappan et al. (2001); Ma et al. (2006); Ma et al. (2007). The present paper is concerned with the crystal structure of a new cobalt phosphonate complex with a (2-pyridyl-N-oxide)phosphonate ligand.

The asymmetric unit contains half of the [Co(C₅H₄NOPO₃H)₂(H₂O)₂] molecule. As shown in Fig. 1, atom Co1 lies on an inversion centre and is coordinated by four O atoms [O1, O1ⁱ, O4 and O4ⁱ] from two ligands, and two O atoms from two aqua ligands, thereby forming a slightly distorted CoO₆ octahedral coordination geometry. The Co1—O1 and the Co1—O4 distances (Table 1) are close to the value observed in [CoL₂(H₂O)₄] [2.0653 (12) Å, and the Co—O(H₂O) distance in the title structure is close to the value observed in the Co-tetraaqua compound [2.0764 (13) Å with L = 4-hydroxypyridine-2,6-dicarboxylate (Cui et al., 2006)] (Table 1). The cisoid angles of CoO₆ (Table 1) are close to 90°. The phosphonate serves as a chelating ligand using one pyridyl N-oxide acceptor O atom and one phosphonate oxygen atom. One phosphonate oxygen is protonated with the P1—O3 distance 1.560 (3) Å.

In the complex, three classic intermolecular O—H···O hydrogen-bonds exist between the water molecule and a phosphonate O atom, the water molecule and a pyridyl N-oxide acceptor O atom, and between two phosphonate O atoms (Fig. 1, Table 2). Thus, the molecules are interlinked by these hydrogen bonds, forming a one-dimensional chain structure along the a-axis (Fig.2). Additionally, weak intermolecular C—H···O hydrogen bonding contacts (Desiraju & Steiner, 2001) link these chains to form a three-dimensional supramolecular network (Fig. 3).

Related literature

For new open frameworks based on metal pyridylphosphonates, see: Ayyappan et al. (2001). For two-dimensional Cu-phosphonates, see: Ma et al. (2006). For one-dimensional Cu-phosphonates containing bridging ligands, see: Ma et al. (2007). For catalytic and magnetic properties of metal phosphonates, see: Cao et al. (1992). For the layered structures of monophosphonic acids and transition metal ions, see Clearfield (1998). For a tetraaqua-Co(II)-4-hydroxypyridine-2,6-dicarboxylate structure, see: Cui et al. (2006). For weak C—H···O hydrogen-bonding contacts, see: Desiraju & Steiner (2001). For the synthesis of the ligand (2-pyridyl-N-oxide)phosphonic acid, see: McCabe et al. (1987).

S2. Experimental

The synthesis of the ligand (2-pyridyl-N-oxide)phosphonic acid, see: McCabe et al. (1987). The (2-pyridyl-N-oxide)phosphonic acid (0.0176 g, 0.1 mmol) was dissolved in distilled water (5 ml), and was added a solution of Co(NO₃)₂^.6H₂O (0.0240 g, 0.01 mmol) in distilled water (2 ml). The mixture was stirred at room temperature for 5 h and then filtered. Slow evaporation of the solvent gave pink crystals. (Yield 45%).

S3. Refinement

Carbon-bound H atoms were positioned geometrically (C—H = 0.93 Å), and were included in the refinement in the riding mode approximation, with U_iso(H) = 1.2U_eq(C). The water H atoms and P—O—H H atom were located in a difference Fourier map and restrained to 0.77 (4) Å and 0.85 (4) Å, respectively, with U_iso(H) refined between 1.0 and 1.8U_eq(O).

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, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL/PC (Sheldrick, 2008); software used to prepare material for publication: SHELXTL/PC (Sheldrick, 2008) and PLATON (Spek, 2003).

Figures

	Fig. 1. A view of the compound with the atomic numbering scheme. Displacement ellipsoids were drawn at the 40% probability level. [Symmetry code i = (-x, -y, -z + 1)]
	Fig. 2. One-dimensional supramolecular chain structure with classic O—H···O hydrogen bonds shown with dashed lines, running along the a axis.
	Fig. 3. The cell packing diagram indicating weak C—H···O links with dashed lines, viewed down the a axis.

Diaquabis(2-pyridylphosphonato N-oxide-κ²O¹,O²)cobalt(II)

Crystal data

[Co(C5H5NO4P)2(H2O)2]	F(000) = 450
Mr = 443.10	Dx = 1.822 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 6955 reflections
a = 4.7899 (10) Å	θ = 3.4–27.7°
b = 12.075 (2) Å	µ = 1.32 mm^−1
c = 14.162 (3) Å	T = 293 K
β = 99.51 (3)°	Needle, pink
V = 807.8 (3) Å^3	0.5 × 0.3 × 0.2 mm
Z = 2

Data collection

Rigaku MACHINE? diffractometer	1848 independent reflections
Radiation source: fine-focus sealed tube	1373 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.083
Detector resolution: 13.6612 pixels mm^-1	θmax = 27.5°, θmin = 3.4°
dtfind.ref scans	h = −6→6
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −15→15
Tmin = 0.625, Tmax = 0.766	l = −18→18
8068 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)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.109	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0457P)^2 + 0.1404P] where P = (Fo^2 + 2Fc^2)/3
1848 reflections	(Δ/σ)max < 0.001
127 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.45 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
Co1	0.0000	0.0000	0.5000	0.0251 (2)
P1	0.06589 (18)	0.23457 (7)	0.41631 (6)	0.0247 (2)
O1	0.2057 (5)	0.14984 (17)	0.48661 (15)	0.0265 (5)
O2	−0.1949 (5)	0.2903 (2)	0.43729 (17)	0.0367 (6)
O3	0.2811 (5)	0.3247 (2)	0.39564 (18)	0.0328 (6)
H3A	0.455 (9)	0.307 (3)	0.406 (3)	0.055 (14)*
O4	−0.2925 (5)	0.0442 (2)	0.37548 (16)	0.0326 (6)
O1W	0.2669 (6)	−0.0782 (3)	0.4170 (2)	0.0317 (6)
H1WA	0.362 (8)	−0.043 (3)	0.389 (3)	0.031 (12)*
H1WB	0.362 (9)	−0.120 (4)	0.449 (3)	0.057 (17)*
N1	−0.1928 (6)	0.0750 (2)	0.29606 (19)	0.0281 (7)
C1	−0.0157 (7)	0.1641 (3)	0.3010 (2)	0.0273 (8)
C2	0.0908 (8)	0.1928 (3)	0.2193 (3)	0.0365 (9)
H2	0.2141	0.2525	0.2210	0.044*
C3	0.0168 (9)	0.1342 (3)	0.1355 (3)	0.0450 (10)
H3	0.0910	0.1534	0.0811	0.054*
C4	−0.1695 (9)	0.0462 (4)	0.1332 (3)	0.0465 (11)
H4	−0.2257	0.0071	0.0767	0.056*
C5	−0.2703 (9)	0.0173 (3)	0.2146 (3)	0.0407 (10)
H5	−0.3930	−0.0426	0.2138	0.049*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.0192 (4)	0.0303 (4)	0.0261 (4)	−0.0024 (3)	0.0050 (3)	0.0041 (3)
P1	0.0175 (5)	0.0272 (5)	0.0299 (5)	−0.0009 (4)	0.0049 (4)	0.0017 (4)
O1	0.0208 (12)	0.0281 (12)	0.0301 (13)	−0.0053 (10)	0.0031 (10)	0.0049 (10)
O2	0.0216 (14)	0.0389 (15)	0.0494 (16)	0.0026 (12)	0.0056 (12)	−0.0042 (12)
O3	0.0177 (14)	0.0330 (14)	0.0464 (16)	−0.0028 (12)	0.0010 (12)	0.0074 (11)
O4	0.0244 (14)	0.0436 (15)	0.0301 (13)	−0.0085 (11)	0.0050 (11)	0.0067 (11)
O1W	0.0271 (15)	0.0354 (16)	0.0339 (16)	−0.0008 (14)	0.0084 (13)	0.0033 (13)
N1	0.0279 (16)	0.0325 (16)	0.0232 (15)	0.0009 (14)	0.0020 (12)	0.0032 (12)
C1	0.0207 (18)	0.0320 (19)	0.0288 (18)	0.0021 (16)	0.0033 (15)	0.0034 (15)
C2	0.035 (2)	0.040 (2)	0.037 (2)	0.0009 (18)	0.0113 (18)	0.0096 (17)
C3	0.056 (3)	0.053 (3)	0.028 (2)	0.011 (2)	0.0147 (19)	0.0060 (18)
C4	0.062 (3)	0.044 (2)	0.031 (2)	0.010 (2)	0.002 (2)	−0.0053 (18)
C5	0.046 (3)	0.037 (2)	0.037 (2)	−0.0031 (19)	−0.0016 (19)	−0.0040 (17)

Geometric parameters (Å, º)

Co1—O1	2.084 (2)	O1W—H1WA	0.77 (4)
Co1—O1^i	2.084 (2)	O1W—H1WB	0.77 (4)
Co1—O1W^i	2.099 (3)	N1—C5	1.346 (4)
Co1—O1W	2.099 (3)	N1—C1	1.365 (4)
Co1—O4	2.131 (2)	C1—C2	1.383 (5)
Co1—O4^i	2.131 (2)	C2—C3	1.377 (5)
P1—O2	1.491 (2)	C2—H2	0.9300
P1—O1	1.505 (2)	C3—C4	1.384 (6)
P1—O3	1.560 (3)	C3—H3	0.9300
P1—C1	1.826 (3)	C4—C5	1.367 (5)
O3—H3A	0.85 (4)	C4—H4	0.9300
O4—N1	1.345 (3)	C5—H5	0.9300
O1—Co1—O1^i	180.0	N1—O4—Co1	119.04 (18)
O1—Co1—O1W^i	90.07 (11)	Co1—O1W—H1WA	120 (3)
O1^i—Co1—O1W^i	89.93 (11)	Co1—O1W—H1WB	108 (3)
O1—Co1—O1W	89.93 (11)	H1WA—O1W—H1WB	108 (4)
O1^i—Co1—O1W	90.07 (11)	O4—N1—C5	119.2 (3)
O1W^i—Co1—O1W	180.000 (1)	O4—N1—C1	118.6 (3)
O1—Co1—O4	87.91 (9)	C5—N1—C1	122.2 (3)
O1^i—Co1—O4	92.09 (9)	N1—C1—C2	117.8 (3)
O1W^i—Co1—O4	88.45 (10)	N1—C1—P1	116.9 (2)
O1W—Co1—O4	91.55 (10)	C2—C1—P1	125.3 (3)
O1—Co1—O4^i	92.09 (9)	C3—C2—C1	120.9 (4)
O1^i—Co1—O4^i	87.91 (9)	C3—C2—H2	119.5
O1W^i—Co1—O4^i	91.55 (10)	C1—C2—H2	119.5
O1W—Co1—O4^i	88.45 (10)	C2—C3—C4	119.2 (4)
O4—Co1—O4^i	180.00 (9)	C2—C3—H3	120.4
O2—P1—O1	118.07 (14)	C4—C3—H3	120.4
O2—P1—O3	108.89 (15)	C5—C4—C3	119.5 (4)
O1—P1—O3	111.28 (14)	C5—C4—H4	120.2
O2—P1—C1	109.02 (15)	C3—C4—H4	120.2
O1—P1—C1	106.32 (14)	N1—C5—C4	120.3 (4)
O3—P1—C1	101.99 (15)	N1—C5—H5	119.9
P1—O1—Co1	119.01 (13)	C4—C5—H5	119.9
P1—O3—H3A	117 (3)
O2—P1—O1—Co1	68.83 (18)	O4—N1—C1—P1	−0.7 (4)
O3—P1—O1—Co1	−164.20 (13)	C5—N1—C1—P1	179.3 (3)
C1—P1—O1—Co1	−53.93 (18)	O2—P1—C1—N1	−68.0 (3)
O1W^i—Co1—O1—P1	−78.04 (16)	O1—P1—C1—N1	60.3 (3)
O1W—Co1—O1—P1	101.96 (16)	O3—P1—C1—N1	176.9 (2)
O4—Co1—O1—P1	10.41 (15)	O2—P1—C1—C2	113.0 (3)
O4^i—Co1—O1—P1	−169.59 (15)	O1—P1—C1—C2	−118.7 (3)
O1—Co1—O4—N1	52.1 (2)	O3—P1—C1—C2	−2.0 (3)
O1^i—Co1—O4—N1	−127.9 (2)	N1—C1—C2—C3	0.9 (5)
O1W^i—Co1—O4—N1	142.2 (2)	P1—C1—C2—C3	179.9 (3)
O1W—Co1—O4—N1	−37.8 (2)	C1—C2—C3—C4	0.8 (6)
Co1—O4—N1—C5	121.0 (3)	C2—C3—C4—C5	−1.8 (6)
Co1—O4—N1—C1	−59.0 (3)	O4—N1—C5—C4	−179.3 (3)
O4—N1—C1—C2	178.3 (3)	C1—N1—C5—C4	0.7 (5)
C5—N1—C1—C2	−1.7 (5)	C3—C4—C5—N1	1.1 (6)

Symmetry code: (i) −x, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1WB···O1^ii	0.77 (4)	2.15 (5)	2.803 (4)	142 (4)
O3—H3A···O2^iii	0.85 (4)	1.68 (4)	2.516 (3)	171 (4)
O1W—H1WA···O4^iii	0.77 (4)	2.00 (4)	2.719 (4)	155 (4)
C3—H3···O2^iv	0.93	2.52	3.449 (5)	178

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