Calcium sodium imino­disulphonate trihydrate, a product of flue-gas desulfurization

One of the crystalline products resulting from the removal of sulfur dioxide from flue gas has been shown to be calcium sodium imino­di­sulfonate trihydrate, CaNa[N(SO₃)₂]·3H₂O.

Key indicators

• Single-crystal X-ray study
• T = 300 K
• Mean [sigma](S-N) = 0.001 Å
• R factor = 0.021
• wR factor = 0.029
• Data-to-parameter ratio = 13.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



CHEMS_01  Alert B The sum formula contains elements in the wrong order.
          H  precedes Ca
          Sequence must be C, H, then alphabetical.


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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S1. Comment

The removal of sulfur dioxide in the flue gas from the Enstedv{ae}rk power plant in Aabenraa is effected by treating the flue gas with am aerated slurry containing calcium carbonate. The primary product is gypsum but the content of, for example, NO, NO₂, HCl and HF in the flue gas leads to a complex chemistry, resulting in the presence of a large number of species formed through reaction. Among other compounds sulfonic acid derivatives of ammonia and hydroxylamines are known to be present and they contribute up to 500 mg_N l^-1 to the total nitrogen content in the slurry filtrate. Soluble species are removed through a bleed stream of slurry filtrate that is treated in order to remove heavy metals and residual suspended matter before it is pumped through a 3 km long pipeline to a municipal waste water plant for final treatment and discharge into the sea. Large, up to 1 cm², crystals of an unidentified compound were found in both the heavy-metal precipitation plant and the pipeline. The temperature is 313–323 K, the pH is close to 9 and the major ions present in the slurry filtrate are Ca²⁺, Na⁺, Mg²⁺, Cl^-, SO₄^2-, SO₃^2- and CO₃^2-. Since the crystals could not be identified from a powder pattern, a single-crystal study was carried out, which showed the crystals to be the known compound calcium sodium iminodisulfonate trihydrate, CaNa[N(SO₃)₂]·3H₂O, (I).

The compound was first reported by Divers & Haga (1892), who obtained it when attempting to make the Ca salt by treating the Na salt with the required amount of CaCl₂; this suggests that the mixed Ca/Na salt is less soluble than either the Na or the Ca salt. The iminodisulfonate ion (Fig. 1) has approximate mirror symmetry, with atoms S1, S2, N1, O2 and O6 in the mirror plane. The geometry of the imidosulfonate ion is similar to that found in the potassium salt (Barbier et al., 1979; Hall et al., 1980). The shortness of the S—N bond is usually attributed (e.g. Cruickshank, 1961) to dπ–pπ bonding; the [N(SO₃)₂]^3- ion has shorter S—N distances (0.064 Å) and longer S—O distances (0.018 Å) than the [HN(SO₃)₂]^2- ion (Barbier et al., 1979), indicating a greater degree of S═N double bonding. The Ca²⁺ ion is surrounded by five sulfonate O atoms, two water molecules and the N atom, which form a very irregular dodecahedron, with Ca···O distances in the range 2.391 (1)–2.756 (1) Å; the Ca···N distance of 2.559 (1) Å is similar to that, 2.58 Å found in eight-coordinated CaN₈ arrangements (Hazell et al., 1999). The Na⁺ ion is surrounded by an octahedral arrangement of four sulfonate O atoms and two water molecules at distances in the range 2.304 (1)–2.514 (1) Å. There is an extensive system of hydrogen bonding (Table 2) involving the water molecules and atoms O2, O5 and O6 of the iminodisulfonate ion (Fig 2). Water molecules O7 and O9 are both disorded so that one of the the associated H atoms in each case is disordered over two sites (HO7a/HO7b and HO9b/HO9c); thus, for the hydrogen bonds between O7 and O7', O9 and O9', and O7 and O9, there are two half-H atoms.

S2. Refinement

H atoms were located from a difference synthesis plotted on the surface of a sphere of radius 0.9 Å about the O atoms of the water molecules. Site-occupation factors for HO7c and HO9c were required to be 0.5 from symmetry considerations, and so those for HO7b and HO9b were also 0.5.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1997) and KRYSTAL (Hazell, 1995); program(s) used to refine structure: modified ORFLS (Busing et al., 1962) and KRYSTAL; molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and KRYSTAL; software used to prepare material for publication: KRYSTAL.

Figures

	Fig. 1. View of the [N(SO3)2]^3- anion, showing the labelling of atoms. Displacement ellipsoids are shown at 50% probability levels. Colour code: S black, O red, and N blue.
	Fig. 2. The cell contents, showing the hydrogen bonding; b is across the page and c down the page. Colour code: Ca magenta, Na green, S black, O red, and H open black circles.

calcium sodium iminodisulfonate trihydrate

Crystal data

CaNa[N(SO3)2]·3H2O	F(000) = 592.0
Mr = 291.19	Dx = 2.296 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8369 reflections
a = 7.4416 (3) Å	θ = 2.7–29.8°
b = 11.1779 (4) Å	µ = 1.32 mm^−1
c = 10.4536 (4) Å	T = 300 K
β = 104.431 (1)°	Plate, colorless
V = 842.11 (6) Å^3	0.36 × 0.22 × 0.06 mm
Z = 4

Data collection

Siemens SMART CCD diffractometer	2444 independent reflections
Radiation source: x-ray tube	2112 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.040
ω rotation scans with narrow frames	θmax = 29.8°, θmin = 2.7°
Absorption correction: integration (XPREP; Siemens, 1995)	h = −10→10
Tmin = 0.690, Tmax = 0.925	k = −14→14
12384 measured reflections	l = −14→14

Refinement

Refinement on F	0 constraints
Least-squares matrix: full	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.021	w = 1/{[σcs(F^2) + B + (1 + A)F^2]^1/2- |F|}^2 where A = 0.03, B = 0.1
wR(F^2) = 0.029	(Δ/σ)max = 0.001
S = 1.12	Δρmax = 0.50 (7) e Å^−3
2112 reflections	Δρmin = −0.50 (7) e Å^−3
160 parameters	Extinction correction: B-C type 1 Lorentzian isotropic (Becker and Coppens, 1974)
0 restraints	Extinction coefficient: 23 (5)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ca1	0.40583 (4)	0.60061 (3)	0.68246 (3)	0.0129 (1)
S1	0.59548 (5)	0.79818 (3)	0.95491 (3)	0.0122 (2)
S2	0.25515 (5)	0.87390 (3)	0.80736 (3)	0.0132 (2)
Na1	0.11111 (9)	1.18369 (6)	0.71825 (6)	0.0229 (3)
O1	0.6919 (2)	0.9030 (1)	0.9199 (1)	0.0217 (6)
O2	0.6635 (2)	0.7667 (1)	1.0947 (1)	0.0204 (6)
O3	0.6141 (2)	0.6968 (1)	0.8703 (1)	0.0196 (6)
O4	0.3018 (1)	0.9974 (1)	0.7817 (1)	0.0183 (5)
O5	0.2828 (2)	0.7957 (1)	0.7009 (1)	0.0224 (6)
O6	0.0650 (2)	0.8663 (1)	0.8220 (1)	0.0249 (6)
O7	−0.0903 (2)	1.0942 (1)	0.5403 (1)	0.0280 (7)
O8	0.0659 (2)	0.5870 (1)	0.6346 (1)	0.0231 (6)
O9	0.3686 (2)	0.4863 (1)	0.8728 (1)	0.0259 (7)
N1	0.3821 (2)	0.8286 (1)	0.9461 (1)	0.0164 (6)
HO7a	−0.144 (4)	1.137 (3)	0.475 (3)	0.056 (8)*
HO7b	−0.202 (8)	1.061 (5)	0.558 (5)	0.046 (14)*	0.5
HO7c	−0.034 (6)	1.040 (4)	0.516 (4)	0.027 (11)*	0.5
HO8a	0.013 (4)	0.610 (3)	0.565 (3)	0.053 (8)*
HO8b	0.032 (4)	0.512 (3)	0.653 (3)	0.054 (8)*
HO9a	0.355 (4)	0.412 (3)	0.871 (2)	0.048 (7)*
HO9b	0.270 (7)	0.519 (4)	0.894 (4)	0.025 (11)*	0.5
HO9c	0.449 (7)	0.504 (4)	0.938 (4)	0.038 (13)*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ca1	0.0141 (1)	0.0116 (1)	0.0134 (1)	0.0011 (1)	0.0043 (1)	−0.0008 (1)
S1	0.0137 (2)	0.0114 (2)	0.0114 (2)	−0.0003 (1)	0.0033 (1)	−0.0005 (1)
S2	0.0117 (2)	0.0101 (2)	0.0176 (2)	0.0001 (1)	0.0033 (1)	−0.0009 (1)
Na1	0.0181 (3)	0.0257 (3)	0.0230 (3)	0.0008 (2)	0.0012 (2)	−0.0008 (3)
O1	0.0202 (5)	0.0197 (6)	0.0261 (6)	−0.0046 (4)	0.0075 (5)	0.0049 (4)
O2	0.0263 (6)	0.0193 (5)	0.0131 (5)	−0.0018 (4)	0.0002 (4)	0.0009 (4)
O3	0.0197 (5)	0.0203 (5)	0.0182 (5)	0.0040 (4)	0.0034 (4)	−0.0065 (4)
O4	0.0181 (5)	0.0123 (5)	0.0246 (5)	−0.0007 (4)	0.0052 (4)	0.0021 (4)
O5	0.0282 (6)	0.0179 (5)	0.0175 (5)	0.0065 (4)	−0.0012 (4)	−0.0053 (4)
O6	0.0135 (5)	0.0199 (6)	0.0421 (7)	−0.0004 (4)	0.0085 (5)	0.0020 (5)
O7	0.0278 (7)	0.0315 (7)	0.0226 (6)	0.0041 (5)	0.0022 (5)	−0.0013 (5)
O8	0.0188 (5)	0.0209 (6)	0.0291 (7)	−0.0005 (4)	0.0048 (5)	−0.0009 (5)
O9	0.0334 (7)	0.0210 (6)	0.0233 (6)	−0.0042 (5)	0.0070 (5)	0.0027 (5)
N1	0.0161 (6)	0.0190 (6)	0.0154 (6)	0.0021 (5)	0.0068 (5)	0.0009 (5)

Geometric parameters (Å, º)

S1—O1	1.467 (1)	Ca1—N1^ii	2.559 (1)
S1—O2	1.465 (1)	Na1—O2^iii	2.304 (1)
S1—O3	1.465 (1)	Na1—O3^iv	2.450 (1)
S1—N1	1.604 (1)	Na1—O4	2.514 (1)
S2—O4	1.464 (1)	Na1—O6^v	2.406 (1)
S2—O5	1.470 (1)	Na1—O7	2.306 (2)
S2—O6	1.463 (1)	Na1—O8^v	2.506 (1)
S2—N1	1.602 (1)	O7—HO7a	0.85 (3)
Ca1—O1^i	2.483 (1)	O7—HO7b	0.97 (7)
Ca1—O2^ii	2.756 (1)	O7—HO7c	0.81 (4)
Ca1—O3	2.428 (1)	O8—HO8a	0.78 (3)
Ca1—O4^i	2.408 (1)	O8—HO8b	0.91 (3)
Ca1—O5	2.391 (1)	O9—HO9a	0.83 (3)
Ca1—O8	2.458 (1)	O9—HO9b	0.90 (5)
Ca1—O9	2.438 (1)	O9—HO9c	0.81 (5)
O1—S1—O2	111.80 (7)	O4^i—Ca1—O8	147.79 (4)
O1—S1—O3	109.97 (7)	O4^i—Ca1—O9	84.49 (4)
O1—S1—N1	110.81 (7)	O4^i—Ca1—N1^ii	98.08 (4)
O2—S1—O3	110.81 (7)	O5—Ca1—O8	71.20 (4)
O2—S1—N1	101.49 (7)	O5—Ca1—O9	106.78 (5)
O3—S1—N1	111.74 (6)	O5—Ca1—N1^ii	81.95 (4)
O4—S2—O5	109.75 (7)	O8—Ca1—O9	79.25 (5)
O4—S2—O6	110.67 (6)	O8—Ca1—N1^ii	90.14 (4)
O4—S2—N1	110.51 (7)	O9—Ca1—N1^ii	162.92 (5)
O5—S2—O6	111.49 (7)	O2^iii—Na1—O3^iv	78.85 (4)
O5—S2—N1	109.57 (6)	O2^iii—Na1—O4	74.43 (4)
O6—S2—N1	104.75 (7)	O2^iii—Na1—O6^v	101.18 (5)
S1—N1—S2	118.10 (7)	O2^iii—Na1—O7	168.04 (6)
O1^i—Ca1—O2^ii	119.25 (4)	O2^iii—Na1—O8^v	88.03 (5)
O1^i—Ca1—O3	143.30 (4)	O3^iv—Na1—O4	71.33 (4)
O1^i—Ca1—O4^i	78.30 (4)	O3^iv—Na1—O6^v	110.67 (5)
O1^i—Ca1—O5	140.26 (4)	O3^iv—Na1—O7	99.02 (5)
O1^i—Ca1—O8	71.39 (4)	O3^iv—Na1—O8^v	150.87 (5)
O1^i—Ca1—O9	78.76 (4)	O4—Na1—O6^v	174.91 (6)
O1^i—Ca1—N1^ii	85.21 (4)	O4—Na1—O7	93.70 (5)
O2^ii—Ca1—O3	70.98 (3)	O4—Na1—O8^v	80.16 (4)
O2^ii—Ca1—O4^i	68.46 (4)	O6^v—Na1—O7	90.61 (5)
O2^ii—Ca1—O5	81.26 (4)	O6^v—Na1—O8^v	97.27 (4)
O2^ii—Ca1—O8	137.03 (4)	O7—Na1—O8^v	88.45 (5)
O2^ii—Ca1—O9	141.60 (4)	HO7a—O7—HO7b	97 (3)
O2^ii—Ca1—N1^ii	53.02 (3)	HO7a—O7—HO7c	110 (4)
O3—Ca1—O4^i	73.53 (4)	HO7b—O7—HO7c	108 (4)
O3—Ca1—O5	73.22 (4)	HO8a—O8—HO8b	113 (3)
O3—Ca1—O8	127.54 (4)	HO9a—O9—HO9b	108 (4)
O3—Ca1—O9	75.60 (4)	HO9a—O9—HO9c	108 (4)
O3—Ca1—N1^ii	121.38 (4)	HO9b—O9—HO9c	100 (4)
O4^i—Ca1—O5	140.68 (4)

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