Tetraaqua­bis[2-(4-pyridyl)ethanesul­fonato-N]­zinc(II)

The title compound, [Zn(C₇H₈NO₃S)₂(H₂O)₄], has an octahedral coordination around the central Zn atom composed of two axial N atoms from the pyridine ligands and four equatorial O atoms of water mol­ecules, forming a monomeric centrosymmetric complex. The two Zn-N bond distances are 2.102 (3) Å, while the four Zn-O bond distances range from 2.114 (2) to 2.167 (2) Å. Packing is determined by hydrogen bonds formed by the water mol­ecules. The sulfonate group does not take part in coordination to the Zn atom.

S1. Comment

There has been considerable interest in pyridineethanesulfonic acid as a bifunctional ligand of new ternary radiopharmaceutical complexes (Costanzo et al., 1997; Edwards & Shuang, 1997; Shuang et al., 1998), but we have not found any report about the crystal structure of complexes it can form with metal ions. Recently, one of us has prepared a few complexes having two-dimensional square grids by hydrothermal synthesis method (Xiong et al., 1998; Lin et al., 1998; Owen, Wang et al., 1999; Owen, Xiong et al., 1999; Xiong et al., 1999), and tried to synthetize new complexes made by the 4-pyridineethanesulfonic acid (PES).

In this paper, we report on the crystal structure of the title compound, (I), which represents the first example of a metal complex with PES. The X-ray crystal structure determination shows that the N atom of the pyridine ring of PES coordinates to the zinc atom, but the sulfonate group of PES is not involved in coordination to metal, so a centrosymmetric monomer is formed with four water molecules equatorially coordinating in a plane while two N atoms occupy the axial positions, instead of constructing two- and three-dimensional supramolecular networks, as shown in Figure 1. The environment around the central Zn atom is an almost perfect octahedron with an N—Zn—N bond angle of 180° and an N—Zn—O bond angle near to 90°, similar to that of bis(N-isonicotinato) tetraaquazinc(II) (Biagini et al., 1971) in which two carboxylato ligands are not involved in coordination to zinc. The Zn—O bond distances Zn1—O2 and Zn1—O3 are 2.167 (2) and 2.114 (2) Å, respectively, while the Zn1—N1 bond distance is 2.102 (3) Å. The bond distances of C—C, C═C, S—O and N═C are unexceptional. \sch

The complex molecules are packed in the crystal by a hydrogen-bonding system involving the water molecules whose relevant geometric parameters are quoted in Table 1. The molecules of complexes are piled up in turn as layers through strong intermolecular O2W—H1—O2, O1W—H3—O1 and O1W—H4—O3 hydrogen bonds. These layers are linked through O2W—H2—O3 strong hydrogen bonds and weak C4—H4A—O2 ones to form three-dimensional network structure. Futher work will be focused on solvothermal synthesis to eliminate the coordinated water and have the sulfonate group connecting metal centres to construct one-, two- and three-dimensional supramolecular frameworks.

S2. Experimental

4-Pyridineethanesulfonic acid (0.1 g) and Zn(ClO₄)₂·2H₂O (0.1 g) were added to water (10 ml) and pyridine (0.12 ml). The resulting solution was evaporated at room temperature for a few days. Colorless block-shaped crystals were obtained. The IR spectrum displayed a strong absorption band at 3350 cm⁻¹.

Computing details

Data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS; data reduction: SHELXTL (Sheldrick, 1997); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are shown at 35% probability levels.

Bis(4-Pyridineethanesulfonato-N) Tetraaquazinc

Crystal data

[Zn(C7H8NO3S)2(H2O)4]	F(000) = 528
Mr = 509.84	Dx = 1.691 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.0967 (14) Å	Cell parameters from 45 reflections
b = 8.8122 (13) Å	θ = 5.2–11.8°
c = 12.5396 (14) Å	µ = 1.49 mm^−1
β = 94.91 (1)°	T = 293 K
V = 1001.5 (2) Å^3	Block, colourless
Z = 2	0.60 × 0.40 × 0.15 mm

Data collection

Bruker P4 diffractometer	1429 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.023
Graphite monochromator	θmax = 25.0°, θmin = 2.3°
2θ/ω scans	h = −1→10
Absorption correction: empirical (using intensity measurements) (North et al., 1968)	k = −1→10
Tmin = 0.618, Tmax = 0.800	l = −14→14
2411 measured reflections	3 standard reflections every 97 reflections
1765 independent reflections	intensity decay: 6.1%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.033	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.092	w = 1/[σ^2(Fo^2) + (0.0494P)^2 + 1.0422P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.001
1765 reflections	Δρmax = 0.76 e Å^−3
134 parameters	Δρmin = −0.56 e Å^−3
6 restraints	Extinction correction: SHELXTL (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0129 (17)

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	0.0000	0.0000	0.5000	0.0225 (2)
S1	−0.75531 (10)	0.05693 (10)	0.90620 (6)	0.0267 (3)
N1	−0.1723 (3)	0.0233 (3)	0.6004 (2)	0.0230 (6)
O1	−0.8216 (4)	−0.0820 (3)	0.9369 (2)	0.0524 (8)
O2	−0.6995 (3)	0.1494 (3)	0.99661 (18)	0.0388 (7)
O3	−0.8524 (3)	0.1444 (3)	0.82937 (17)	0.0340 (6)
O1W	−0.0704 (3)	0.2054 (3)	0.42483 (18)	0.0312 (6)
H3	−0.1028	0.2746	0.4644	0.047*
H4	−0.0053	0.2458	0.3884	0.047*
O2W	0.1542 (3)	0.1264 (3)	0.60733 (17)	0.0345 (6)
H1	0.1931	0.2043	0.5804	0.052*
H2	0.1491	0.1431	0.6739	0.052*
C1	−0.3056 (4)	0.0726 (4)	0.5596 (3)	0.0270 (8)
H1A	−0.3225	0.0823	0.4857	0.032*
C2	−0.4177 (4)	0.1094 (4)	0.6214 (3)	0.0292 (8)
H2A	−0.5078	0.1430	0.5893	0.035*
C3	−0.3963 (4)	0.0964 (4)	0.7318 (3)	0.0282 (8)
C4	−0.2609 (4)	0.0404 (4)	0.7735 (3)	0.0300 (8)
H4A	−0.2426	0.0263	0.8470	0.036*
C5	−0.1534 (4)	0.0057 (4)	0.7065 (3)	0.0266 (8)
H5A	−0.0636	−0.0317	0.7364	0.032*
C6	−0.5137 (4)	0.1420 (4)	0.8033 (3)	0.0364 (9)
H6A	−0.5802	0.2142	0.7659	0.044*
H6B	−0.4679	0.1914	0.8668	0.044*
C7	−0.6011 (4)	0.0055 (4)	0.8362 (3)	0.0290 (8)
H7A	−0.5367	−0.0601	0.8813	0.035*
H7B	−0.6354	−0.0515	0.7727	0.035*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0216 (3)	0.0265 (3)	0.0207 (3)	0.0009 (2)	0.0092 (2)	0.0007 (2)
S1	0.0275 (5)	0.0297 (5)	0.0250 (4)	0.0024 (4)	0.0138 (3)	0.0023 (3)
N1	0.0205 (15)	0.0282 (15)	0.0210 (13)	0.0000 (12)	0.0069 (11)	−0.0015 (11)
O1	0.0546 (12)	0.0493 (11)	0.0569 (11)	−0.0025 (9)	0.0247 (9)	0.0042 (9)
O2	0.0363 (15)	0.0558 (17)	0.0247 (11)	0.0112 (13)	0.0046 (10)	−0.0077 (11)
O3	0.0285 (15)	0.0479 (16)	0.0265 (11)	0.0077 (12)	0.0073 (10)	−0.0024 (10)
O1W	0.0324 (14)	0.0287 (13)	0.0346 (12)	0.0028 (11)	0.0150 (10)	0.0046 (10)
O2W	0.0403 (16)	0.0416 (14)	0.0226 (11)	−0.0130 (12)	0.0079 (10)	−0.0030 (10)
C1	0.0245 (19)	0.0338 (19)	0.0229 (15)	0.0009 (16)	0.0038 (14)	0.0003 (13)
C2	0.0196 (18)	0.0317 (18)	0.0369 (18)	0.0006 (15)	0.0057 (15)	0.0007 (15)
C3	0.0284 (19)	0.0221 (16)	0.0368 (17)	−0.0057 (15)	0.0173 (15)	−0.0035 (14)
C4	0.034 (2)	0.0355 (18)	0.0218 (16)	−0.0034 (17)	0.0090 (15)	−0.0030 (14)
C5	0.0218 (19)	0.0322 (18)	0.0262 (16)	−0.0014 (14)	0.0035 (14)	−0.0005 (13)
C6	0.035 (2)	0.0319 (19)	0.046 (2)	−0.0029 (17)	0.0221 (17)	−0.0083 (16)
C7	0.030 (2)	0.0265 (17)	0.0334 (18)	0.0057 (15)	0.0161 (15)	0.0009 (14)

Geometric parameters (Å, º)

Zn1—N1^i	2.102 (3)	S1—C7	1.776 (4)
Zn1—N1	2.102 (3)	N1—C5	1.336 (4)
Zn1—O1W	2.114 (2)	N1—C1	1.347 (4)
Zn1—O1W^i	2.114 (2)	C1—C2	1.372 (5)
Zn1—O2W^i	2.167 (2)	C2—C3	1.386 (5)
Zn1—O2W	2.167 (2)	C3—C4	1.387 (5)
S1—O1	1.432 (3)	C3—C6	1.506 (5)
S1—O2	1.452 (3)	C4—C5	1.377 (5)
S1—O3	1.469 (3)	C6—C7	1.518 (5)
N1^i—Zn1—N1	180.0	O2—S1—O3	111.58 (15)
N1^i—Zn1—O1W	91.68 (10)	O1—S1—C7	106.45 (17)
N1—Zn1—O1W	88.32 (10)	O2—S1—C7	106.94 (17)
N1^i—Zn1—O1W^i	88.32 (10)	O3—S1—C7	105.40 (15)
N1—Zn1—O1W^i	91.68 (10)	C5—N1—C1	116.7 (3)
O1W—Zn1—O1W^i	180.0	C5—N1—Zn1	123.1 (2)
N1^i—Zn1—O2W^i	93.10 (10)	C1—N1—Zn1	119.8 (2)
N1—Zn1—O2W^i	86.90 (10)	N1—C1—C2	123.4 (3)
O1W—Zn1—O2W^i	90.46 (9)	C1—C2—C3	119.8 (3)
O1W^i—Zn1—O2W^i	89.54 (9)	C2—C3—C4	116.7 (3)
N1^i—Zn1—O2W	86.90 (10)	C2—C3—C6	121.8 (3)
N1—Zn1—O2W	93.10 (10)	C4—C3—C6	121.5 (3)
O1W—Zn1—O2W	89.54 (9)	C5—C4—C3	120.2 (3)
O1W^i—Zn1—O2W	90.46 (9)	N1—C5—C4	123.0 (3)
O2W^i—Zn1—O2W	180.0	C3—C6—C7	111.4 (3)
O1—S1—O2	113.39 (17)	C6—C7—S1	112.7 (2)
O1—S1—O3	112.45 (18)

Symmetry code: (i) −x, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2W—H1···O2^ii	0.85 (5)	1.97 (4)	2.814 (4)	167 (2)
O2W—H2···O3^iii	0.85 (3)	1.95 (1)	2.795 (3)	170 (1)
O1W—H3···O1^iv	0.85 (4)	1.93 (6)	2.788 (4)	175 (1)
O1W—H4···O3^ii	0.85 (6)	1.89 (6)	2.743 (4)	170 (1)
C4—H4A···O2^v	0.93 (1)	2.58 (8)	3.379 (4)	143 (1)

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