Sodium hydrogensquarate monohydrate

In the title compound, sodium 2-hydr­oxy-3,4-dioxocyclo­but-1-en-1-olate monohydrate, Na⁺·C₄HO₄^-·H₂O, the Na atom is six-coordinated by the O atoms from four hydrogensquarate anions and two water mol­ecules. The three-dimensional packing is stabilized by a system of hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 290 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.058
• wR factor = 0.145
• Data-to-parameter ratio = 8.4

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low .......       0.95

Alert level C
REFLT03_ALERT_1_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           29.93
           From the CIF: _diffrn_reflns_theta_full          29.93
           From the CIF: _reflns_number_total                760
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns          801
           Completeness (_total/calc)             94.88%
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.21
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...         10

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           29.93
           From the CIF: _reflns_number_total                760
           Count of symmetry unique reflns          801
           Completeness (_total/calc)             94.88%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

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

   2 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
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion

---

Computing details

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Bruno et al., 2002); software used to prepare material for publication: WinGX (Farrugia, 1999).

sodium 2-hydroxy-3,4-dioxocyclobut-1-en-1-olate hydrate

Crystal data

Na^+·C4HO4^−·H2O	F(000) = 156
Mr = 154.05	Dx = 1.867 Mg m^−3
Monoclinic, Pc	Melting point: not measured K
Hall symbol: P -2yc	Mo Kα radiation, λ = 0.71073 Å
a = 3.6239 (10) Å	Cell parameters from 22 reflections
b = 8.1320 (11) Å	θ = 20.2–21.3°
c = 9.392 (4) Å	µ = 0.24 mm^−1
β = 97.97 (3)°	T = 290 K
V = 274.10 (14) Å^3	Prism, colorless
Z = 2	0.26 × 0.25 × 0.24 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	Rint = 0.077
Radiation source: fine-focus sealed tube	θmax = 29.9°, θmin = 2.5°
Graphite monochromator	h = 0→5
non–profiled ω/2θ scans	k = −11→11
1413 measured reflections	l = −13→13
760 independent reflections	3 standard reflections every 120 min
543 reflections with I > 2σ(I)	intensity decay: 2%

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)] = 0.058	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.145	H-atom parameters constrained
S = 1.20	w = 1/[σ^2(Fo^2) + (0.0298P)^2 + 0.6752P] where P = (Fo^2 + 2Fc^2)/3
760 reflections	(Δ/σ)max < 0.001
91 parameters	Δρmax = 0.38 e Å^−3
2 restraints	Δρmin = −0.43 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
C1	0.3223 (18)	0.5547 (8)	0.2768 (7)	0.0166 (13)
C2	0.0859 (18)	0.5585 (9)	0.1439 (7)	0.0175 (14)
C3	0.0926 (19)	0.7337 (9)	0.1359 (8)	0.0188 (14)
C4	0.3383 (19)	0.7378 (8)	0.2784 (8)	0.0188 (14)
Na1	0.4546 (8)	0.1373 (4)	0.3563 (4)	0.0262 (6)
O	0.9008 (14)	0.1342 (6)	0.1946 (5)	0.0280 (12)
H1A	0.8803	0.0357	0.1358	0.034*
H1B	0.8793	0.2304	0.1329	0.034*
O1	0.4713 (17)	0.4414 (6)	0.3569 (6)	0.0225 (10)
O2	−0.0862 (13)	0.4435 (6)	0.0638 (5)	0.0204 (11)
H1	−0.2508	0.4671	−0.0028	0.024*
O3	−0.0347 (15)	0.8401 (6)	0.0462 (6)	0.0253 (12)
O4	0.482 (2)	0.8418 (6)	0.3596 (8)	0.0289 (12)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.018 (3)	0.017 (3)	0.015 (3)	−0.001 (3)	0.000 (2)	0.000 (3)
C2	0.018 (3)	0.016 (3)	0.017 (3)	−0.002 (3)	−0.002 (2)	0.004 (3)
C3	0.021 (3)	0.019 (3)	0.015 (3)	−0.004 (3)	−0.001 (2)	0.001 (3)
C4	0.019 (3)	0.015 (3)	0.020 (3)	−0.003 (3)	−0.004 (3)	0.000 (3)
Na1	0.0257 (13)	0.0232 (13)	0.0268 (13)	−0.0005 (16)	−0.0059 (10)	−0.0056 (17)
O	0.042 (3)	0.017 (2)	0.024 (3)	0.001 (3)	0.001 (2)	0.002 (2)
O1	0.029 (2)	0.019 (2)	0.016 (2)	0.000 (3)	−0.0104 (17)	0.000 (3)
O2	0.025 (2)	0.016 (2)	0.017 (2)	−0.004 (2)	−0.0085 (19)	−0.003 (2)
O3	0.035 (3)	0.018 (2)	0.019 (2)	0.007 (2)	−0.009 (2)	0.002 (2)
O4	0.035 (3)	0.018 (2)	0.030 (2)	−0.005 (3)	−0.010 (2)	−0.004 (3)

Geometric parameters (Å, º)

C1—O1	1.262 (8)	Na1—O	2.367 (6)
C1—C2	1.412 (8)	Na1—O3^ii	2.393 (7)
C1—C4	1.490 (9)	Na1—O4^iii	2.405 (6)
C2—O2	1.304 (7)	Na1—O1	2.474 (6)
C2—C3	1.427 (10)	Na1—O3^iv	2.691 (7)
C3—O3	1.250 (9)	O—Na1^v	2.343 (6)
C3—C4	1.502 (8)	O—H1A	0.9700
C4—O4	1.207 (9)	O—H1B	0.9700
Na1—O^i	2.343 (6)	O2—H1	0.8245
O1—C1—C2	134.4 (7)	O1—Na1—O3^iv	87.0 (2)
O1—C1—C4	135.2 (7)	O^i—Na1—Na1^i	39.93 (14)
C2—C1—C4	90.3 (6)	O—Na1—Na1^i	140.54 (15)
O2—C2—C1	132.6 (7)	O3^ii—Na1—Na1^i	132.06 (16)
O2—C2—C3	134.1 (6)	O4^iii—Na1—Na1^i	92.2 (2)
C1—C2—C3	93.2 (7)	O1—Na1—Na1^i	91.38 (17)
O3—C3—C2	136.0 (7)	O3^iv—Na1—Na1^i	41.32 (14)
O3—C3—C4	134.7 (7)	O^i—Na1—Na1^v	140.07 (14)
C2—C3—C4	89.2 (6)	O—Na1—Na1^v	39.46 (15)
O4—C4—C1	136.0 (7)	O3^ii—Na1—Na1^v	47.94 (16)
O4—C4—C3	136.8 (7)	O4^iii—Na1—Na1^v	87.8 (2)
C1—C4—C3	87.2 (6)	O1—Na1—Na1^v	88.62 (17)
O^i—Na1—O	100.6 (2)	O3^iv—Na1—Na1^v	138.68 (14)
O^i—Na1—O3^ii	171.3 (2)	Na1^i—Na1—Na1^v	180.00 (18)
O—Na1—O3^ii	87.3 (2)	Na1^v—O—Na1	100.6 (2)
O^i—Na1—O4^iii	91.6 (2)	Na1^v—O—H1A	111.6
O—Na1—O4^iii	88.1 (3)	Na1—O—H1A	111.6
O3^ii—Na1—O4^iii	92.3 (2)	Na1^v—O—H1B	111.6
O^i—Na1—O1	91.8 (2)	Na1—O—H1B	111.6
O—Na1—O1	89.6 (2)	H1A—O—H1B	109.4
O3^ii—Na1—O1	84.6 (2)	C1—O1—Na1	136.0 (4)
O4^iii—Na1—O1	176.3 (3)	C2—O2—H1	120.6
O^i—Na1—O3^iv	81.2 (2)	C3—O3—Na1^vi	136.9 (5)
O—Na1—O3^iv	176.3 (2)	C3—O3—Na1^vii	106.1 (5)
O3^ii—Na1—O3^iv	90.7 (2)	Na1^vi—O3—Na1^vii	90.7 (2)
O4^iii—Na1—O3^iv	95.1 (2)	C4—O4—Na1^viii	132.7 (6)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O1^vi	0.82	1.71	2.522 (7)	166
O—H1B···O2^v	0.97	1.86	2.803 (7)	163
O—H1A···O3^ix	0.97	1.84	2.794 (7)	165

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