catena-Poly[[[triaqua­cadmium(II)]-μ-2,2′-[oxalylbis(azanediyl)]diacetato-κ²O,O′] dihydrate]

The structure of the polymeric title complex, {[Cd(C₆H₆N₂O₆)(H₂O)₃]·2H₂O}_n, consists of chains running parallel to [01] in which the oxamidato ligand, deprotonated only at the carboxyl­ate groups, acts as a bridging bis-monodentate ligand. The Cd atom and the O atom of a coordinated water mol­ecule are located on a twofold axis. The coordination geometry around the Cd atom is distorted trigonal-pyramidal. In the crystal structure, neighbouring chains are linked into a three-dimensional network by inter­chain O—H...O and N—H...O hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.023
• wR factor = 0.058
• Data-to-parameter ratio = 13.1

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Cd     --  O2      ..       8.99 su
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C3     -   C3_b   ...       1.53 Ang.
PLAT417_ALERT_2_C Short Inter D-H..H-D       H4W2   ..  H6W2    ..       2.13 Ang.
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1

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 ..........          4

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   4 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
   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

---

S1. Comment

N-Substituted and N,N'-disubstituted oxamides have played an important role in the design of new polymetallic systems. The versatility of these ligands is based on the wide variety of substituted derivatives which can be synthesized, yielding different numbers of chelate rings with different donor atoms, and on their easy cis-trans conformational change affording symmetric and asymmetric oxamidato bridges. A new polymeric cadmium(II) complex bridged by a symmetrical oxamide-N,N'-diacetic acid ligand has been synthesized and its crystal structure is reported herein.

The title compound (Fig. 1) is a polymeric cadmium(II) complex forming one-dimensional chains parallel to [1 0 1]. The Cd and the oxygen atom of a coordinated water molecules are located on a two-fold axis and the midpoint of the oxamide C—C bond on an inversion centre. The ligand is deprotonated only at the terminal carboxylate groups and acts as a bis-monodentate bridge. The coordination geometry around the Cd atom is distorted trigonal pyramidal, with atoms O5, O1 and O1ⁱ [symmetry code: (i) 1-x, y, 1/2-z] at the equatorial plane and atoms O4 and O4ⁱ at the apical positions [O4—Co1—O4ⁱ = 178.29 (8)°]. The sum of the O—Cd—O angles within the equatorial plane is 359.99 (9)°. The structure is similar to that previously reported for the copper(II) complex (Lloret et al., 1992). The cadmium-cadmium separation within the chain 12.369 (4) Å. Strong interchain N—H···O and O—H···O hydrogen bonds (Table 1) result in the formation of a three-dimensional network (Fig. 2).

Related literature

For the crystal structure of the corresponding copper(II) compound, see: Lloret et al. (1992).

S2. Experimental

To a stirred methanol solution (10 ml) containing Cd(NO₃)₂^.3H₂O (0.0581 g, 0.2 mmol) was added dropwise a methanol solution (10 ml) of oxamide-N,N'-diacetic acid (0.0408 g, 0.2 mmol) and piperidine. The mixture was stirred quickly at 323 K for 5 h. The resulting solution at pH = 3 was filtered and the filtrate was kept at room temperature. Green crystals suitable for X-ray analysis were obtained from the filtrate by slow evaporation for 3 days (yield: 65%) Analysis, calculated for C₆H₁₆N₂O₁₁Cd: C 17.81, H 3.99; N 6.92%; found: C 17.89, H 3.97, N, 6.96%.

S3. Refinement

Water H atoms were located in a difference Fourier map and isotropically refined with U_iso(H) = 0.08 Ų. All other H atoms were positioned geometrically and constrained to ride on their parent atoms, with C—H = 0.97 Å, N—H = 0.86 Å, and with U_iso(H) = 1.2U_eq(C, N).

Computing details

Data collection: SMART (Bruker 1998); cell refinement: SAINT (Bruker 1998); data reduction: SAINT (Bruker 1998); 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: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

	Fig. 1. The polymeric structure of the title compound, with displacement ellipsoids drawn at the 30% probability level. Lattice water molecules generated by symmetry are omitted. [Symmetry codes: (A) 3/2-x, 1/2-y, -z; (B) 1-x, y, 1/2-z; (C) 1/2+x, 1/2-y, -1/2+z].
	Fig. 2. Packing diagram of the title compound viewed along the a axis. Interchain H bonds are shown as dashed lines.

catena-Poly[[[triaquacadmium(II)]-µ₂-2,2'- [oxalylbis(azanediyl)]diacetato-κ²O:O'] dihydrate]

Crystal data

[Cd(C6H6N2O6)(H2O)3]·2H2O	F(000) = 808
Mr = 404.61	Dx = 2.019 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 3445 reflections
a = 7.0898 (14) Å	θ = 3.5–25.2°
b = 8.0306 (16) Å	µ = 1.70 mm^−1
c = 23.396 (5) Å	T = 293 K
β = 92.06 (3)°	Block, green
V = 1331.2 (5) Å^3	0.23 × 0.18 × 0.15 mm
Z = 4

Data collection

Bruker SMART CCD diffractometer	1214 independent reflections
Radiation source: fine-focus sealed tube	1171 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ϕ and ω scans	θmax = 25.2°, θmin = 3.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −7→8
Tmin = 0.696, Tmax = 0.785	k = −9→9
3445 measured reflections	l = −25→28

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)] = 0.023	H-atom parameters constrained
wR(F^2) = 0.058	w = 1/[σ^2(Fo^2) + (0.032P)^2 + 1.2127P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
1214 reflections	Δρmax = 0.50 e Å^−3
93 parameters	Δρmin = −0.53 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0057 (5)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
C1	0.6801 (3)	0.3969 (3)	0.15103 (10)	0.0264 (5)
C2	0.7678 (4)	0.4894 (3)	0.10180 (11)	0.0300 (6)
H1A	0.6764	0.5681	0.0859	0.036*
H1B	0.8756	0.5525	0.1166	0.036*
C3	0.7039 (4)	0.3045 (3)	0.02244 (11)	0.0272 (6)
N1	0.8284 (3)	0.3821 (3)	0.05672 (9)	0.0308 (5)
H1	0.9470	0.3680	0.0519	0.037*
O1	0.5996 (2)	0.4896 (2)	0.18701 (8)	0.0328 (4)
O2	0.6869 (3)	0.2444 (3)	0.15559 (9)	0.0407 (5)
O3	0.5325 (3)	0.3144 (2)	0.02483 (9)	0.0377 (5)
O4	0.2191 (3)	0.3021 (2)	0.19554 (8)	0.0304 (4)
H4W1	0.1704	0.2020	0.1897	0.080*
H4W2	0.2397	0.3493	0.1608	0.080*
O5	0.5000	0.0250 (3)	0.2500	0.0437 (7)
H5W	0.5695	−0.0341	0.2305	0.080*
O6	0.2377 (2)	0.4466 (2)	0.09015 (8)	0.0362 (4)
H6W1	0.3381	0.4129	0.0726	0.080*
H6W2	0.2583	0.5541	0.1036	0.080*
Cd	0.5000	0.29781 (3)	0.2500	0.02762 (15)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0266 (12)	0.0301 (13)	0.0225 (12)	−0.0053 (10)	−0.0004 (9)	−0.0037 (11)
C2	0.0376 (14)	0.0280 (13)	0.0250 (13)	−0.0056 (11)	0.0073 (11)	−0.0049 (11)
C3	0.0346 (14)	0.0277 (14)	0.0198 (13)	0.0017 (10)	0.0074 (11)	0.0004 (10)
N1	0.0326 (11)	0.0351 (12)	0.0253 (11)	−0.0017 (9)	0.0091 (9)	−0.0060 (10)
O1	0.0391 (10)	0.0324 (10)	0.0277 (10)	−0.0058 (8)	0.0108 (8)	−0.0048 (8)
O2	0.0580 (13)	0.0273 (10)	0.0375 (12)	0.0003 (10)	0.0107 (10)	0.0027 (9)
O3	0.0310 (11)	0.0460 (12)	0.0364 (11)	0.0035 (8)	0.0058 (9)	−0.0099 (9)
O4	0.0337 (10)	0.0260 (10)	0.0316 (11)	−0.0015 (7)	0.0027 (8)	−0.0023 (7)
O5	0.0417 (15)	0.0282 (14)	0.063 (2)	0.000	0.0247 (14)	0.000
O6	0.0353 (10)	0.0368 (11)	0.0368 (11)	0.0000 (8)	0.0055 (8)	−0.0020 (8)
Cd	0.0324 (2)	0.02517 (19)	0.02557 (19)	0.000	0.00427 (11)	0.000

Geometric parameters (Å, º)

C1—O2	1.230 (3)	O1—Cd	2.2621 (18)
C1—O1	1.274 (3)	O4—Cd	2.326 (2)
C1—C2	1.522 (3)	O4—H4W1	0.8839
C2—N1	1.440 (3)	O4—H4W2	0.9134
C2—H1A	0.9700	O5—Cd	2.191 (3)
C2—H1B	0.9700	O5—H5W	0.8320
C3—O3	1.221 (3)	O6—H6W1	0.8775
C3—O3	1.221 (3)	O6—H6W2	0.9280
C3—N1	1.326 (4)	Cd—O1^ii	2.2621 (18)
C3—C3^i	1.531 (5)	Cd—O4^ii	2.326 (2)
N1—H1	0.8600
O2—C1—O1	122.8 (2)	C1—O1—Cd	100.97 (15)
O2—C1—C2	122.4 (2)	Cd—O4—H4W1	113.2
O1—C1—C2	114.8 (2)	Cd—O4—H4W2	109.4
N1—C2—C1	113.7 (2)	H4W1—O4—H4W2	108.3
N1—C2—H1A	108.8	Cd—O5—H5W	124.8
C1—C2—H1A	108.8	H6W1—O6—H6W2	109.0
N1—C2—H1B	108.8	O5—Cd—O1^ii	132.90 (4)
C1—C2—H1B	108.8	O5—Cd—O1	132.90 (4)
H1A—C2—H1B	107.7	O1^ii—Cd—O1	94.19 (9)
O3—C3—N1	125.7 (2)	O5—Cd—O4	90.86 (4)
O3—C3—N1	125.7 (2)	O1^ii—Cd—O4	93.76 (7)
O3—C3—C3^i	121.3 (3)	O1—Cd—O4	85.08 (7)
O3—C3—C3^i	121.3 (3)	O5—Cd—O4^ii	90.86 (4)
N1—C3—C3^i	113.1 (3)	O1^ii—Cd—O4^ii	85.08 (7)
C3—N1—C2	121.0 (2)	O1—Cd—O4^ii	93.76 (7)
C3—N1—H1	119.5	O4—Cd—O4^ii	178.29 (8)
C2—N1—H1	119.5

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O6^iii	0.86	2.31	3.024 (3)	141
O4—H4W1···O1^iv	0.88	1.78	2.654 (2)	171
O6—H6W2···O2^v	0.93	2.03	2.869 (3)	150
O5—H5W···O4^vi	0.83	1.89	2.717 (3)	170
O4—H4W2···O6	0.91	1.83	2.733 (3)	170
O6—H6W1···O3	0.88	1.97	2.839 (3)	170

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