inorganic compounds
Sodium peroxodisulfate
aSchool of Chemistry, The University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, Scotland
*Correspondence e-mail: d.r.allan@ed.ac.uk
The +·S2O82− consists of a single Na+ cation and half of a peroxodisulfate dianion, the latter lying across a crystallographic inversion centre. The is isostructural with that of potassium peroxodisulfate and it is composed of layers of molecules, partitioned by the Na+ cations, parallel to the (01) plane of the triclinic cell. Neighbouring molecules within each layer are bridged end-to-end by pairs of short S⋯O intermolecular contacts [S⋯O = 3.074 (2) Å].
of disodium peroxodisulfate 2NaComment
Sodium peroxodisulfate, (I), readily forms SO4 radicals in hot aqueous solution. It is a powerful oxidizing and bleaching agent and it can also be used as a polymerization promoter, as well as providing a cleaner alternative to ferric chloride for copper etchant solutions (Serguchev et al., 1980).
Compund (I) crystallizes from aqueous solution in the triclinic P, with one Na+ cation and half of the peroxodisulfate dianion, the latter located across an inversion centre, in the (Fig. 1). Its which is isostructural with that of potassium peroxodisulfate, K2S2O8, [Naumov et al., 1997; ICSD (Belsky et al., 2002) refcode 54024] is composed of layers of peroxodisulfate anions, which are aligned parallel to the (01) plane and partitioned by corrugated layers of Na+ cations (Fig. 2).
The intramolecular S—O distances and O—S—O bond angles for the peroxodisulfate dianion are very simlar to those reported for the potassium analogue (see Table 1). However, the cation environments for the two analogues are quite different. In potassium peroxodisulfate, the K+ cations are coordinated by nine O atoms with interatomic distances ranging from 2.751 (3) to 3.347 (3) Å. For sodium peroxodisulfate, the Na+ cations are coordinated by six O atoms, with Na—O interatomic distances between 2.340 (2) and 2.596 (2) Å. It is interesting to note that in the sodium analogue, the O atom involved in the intramolecular peroxo bond, O1, is not involved in the cation coordinate environment, although it does exhibit the shortest Na—O distance outside this range [Na1—O1 = 3.167 (2) Å]. The K1—O1 distance in the potassium analogue [3.089 (3) Å] is of an intermediate length compared with the other O atoms defining the coordination environment. The overall effect of the Na—O coordination environment in sodium peroxodisulfate is the formation of a three-dimensional network. This is indicated by the polyhedral plot shown in Fig. 3. The Na+ cations form layers of distorted edge-sharing octahedra (shown as the blue polyhedra in Fig. 3), while the tetrahedra formed by each end of the dianions (shown as the yellow polyhedra in Fig. 3) form corner-sharing bridges between the layers.
Perhaps the most striking difference between the two structures concerns the S⋯O intramolecular contact distances. Within the layers, neighbouring anions are aligned end-to-end so that pairs of relatively short S⋯O contacts are formed. In the sodium analogue these contacts are extremely short [S1⋯O3 = 3.074 (2) Å] (Fig. 4), while in the of the potassium analogue these contacts are significantly longer [S1⋯O3 = 3.417 (3) Å].
Experimental
The sample of sodium peroxodisulfate was prepared from anhydrous starting material (of 99% purity, as received from Aldrich) and recrystallized from an aqueous solution by slow evaporation. A suitable crystal was selected from the resulting batch. The sample was cooled to 150 K using an Oxford Cryosystems low-temperature device (Cosier & Glazer, 1986) during data collection.
Crystal data
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Indexing with GEMINI (Sparks, 1999) revealed that the sample was twinned non-merohedrally with two domains. The data set was integrated using the orientation matrix of the stronger subset of reflections, corresponding to the larger domain. During the ROTAX procedure, as implemented in the CRYSTALS package (Cooper et al., 2002), was used to identify the relationship between the two domains. This could be expressed by the matrix (00, 00, 0.667 0.523 1), which corresponds to a twofold rotation about the c* axis. Subsequent indicated that the twin fraction of the second domain was 0.379 (8).
Data collection: SMART (Bruker Nonius, 2001); cell SAINT; data reduction: SAINT (Bruker Nonius, 2003); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS and PLATON (Spek, 2003).
Supporting information
https://doi.org/10.1107/S1600536806004302/jh6041sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806004302/jh6041Isup2.hkl
Data collection: SMART (Bruker–Nonius, 2001); cell
SAINT; data reduction: SAINT (Bruker–Nonius, 2003); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS and PLATON (Spek, 2003).2Na+·O8S22− | Z = 1 |
Mr = 238.11 | F(000) = 118 |
Triclinic, P1 | Dx = 2.603 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 4.780 (2) Å | Cell parameters from 680 reflections |
b = 5.575 (2) Å | θ = 7–57° |
c = 6.091 (3) Å | µ = 1.02 mm−1 |
α = 101.871 (7)° | T = 150 K |
β = 103.337 (7)° | Needle, colourless |
γ = 97.418 (7)° | 0.20 × 0.05 × 0.05 mm |
V = 151.89 (11) Å3 |
Bruker SMART diffractometer | 590 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.021 |
φ and ω scans | θmax = 28.9°, θmin = 3.6° |
Absorption correction: multi-scan SADABS (Sheldrick, 2004) | h = −6→6 |
Tmin = 0.67, Tmax = 0.95 | k = −7→7 |
1326 measured reflections | l = −8→7 |
696 independent reflections |
Refinement on F | 0 restraints |
Least-squares matrix: full | Primary atom site location: structure-invariant direct methods |
R[F2 > 2σ(F2)] = 0.038 | Modified Chebychev polynomial (Watkin, 1994; Prince, 1982) with the coefficients 1.89, -1.11, 1.17 |
wR(F2) = 0.034 | (Δ/σ)max = 0.000217 |
S = 1.06 | Δρmax = 0.48 e Å−3 |
590 reflections | Δρmin = −0.42 e Å−3 |
56 parameters |
Refinement. ABSTM02_ALERT_3_C The ratio of expected to reported Tmax/Tmin(RR') is < 0.90 T min and Tmax reported: 0.670 0.950 T min(prime) and Tmax expected: 0.814 0.950 RR(prime) = 0.824 Please check that your absorption correction is appropriate. PLAT061_ALERT_3_C Tmax/Tmin Range Test RR' too Large ············. 0.82 The crystal was a fine needle and the absorption correction correspondingly anisotropic. PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low ······. 0.97 This value is only marginally smaller than the ideal (0.99). PLAT432_ALERT_2_C Short Inter X···Y Contact S1.. O3.. 3.07 A ng. This short intermolecular contact bridges persulfate molecules end-on to form infinite chains. This interaction is similar to that observed by Naumov et al. (1997) for the isostructural potassium persulfate where the molecules are also bridged by short S···O intermolecular bonds. In this instance, however, the distance is 3.417 A ng. |
x | y | z | Uiso*/Ueq | ||
Na1 | 0.0359 (2) | 0.31397 (19) | 0.20685 (18) | 0.0131 | |
S1 | 0.61154 (13) | 0.78124 (11) | 0.24744 (11) | 0.0080 | |
O1 | 0.5785 (4) | 1.0388 (3) | 0.4180 (3) | 0.0143 | |
O2 | 0.7722 (4) | 0.8959 (3) | 0.1113 (3) | 0.0113 | |
O3 | 0.3176 (4) | 0.6526 (3) | 0.1263 (3) | 0.0111 | |
O4 | 0.7701 (4) | 0.6451 (3) | 0.3949 (3) | 0.0130 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Na1 | 0.0141 (5) | 0.0136 (5) | 0.0102 (5) | 0.0005 (4) | 0.0012 (4) | 0.0032 (4) |
S1 | 0.0088 (3) | 0.0082 (3) | 0.0068 (3) | 0.00165 (19) | 0.0025 (2) | 0.00122 (19) |
O1 | 0.0223 (10) | 0.0094 (8) | 0.0132 (9) | −0.0009 (7) | 0.0125 (8) | 0.0006 (7) |
O2 | 0.0135 (9) | 0.0106 (8) | 0.0112 (8) | 0.0013 (7) | 0.0063 (7) | 0.0031 (6) |
O3 | 0.0099 (9) | 0.0106 (8) | 0.0114 (8) | 0.0004 (7) | 0.0016 (7) | 0.0017 (7) |
O4 | 0.0119 (9) | 0.0165 (9) | 0.0116 (9) | 0.0046 (7) | 0.0013 (7) | 0.0065 (7) |
S1—O1 | 1.6392 (19) | Na1—O3ii | 2.380 (2) |
S1—O2 | 1.4389 (18) | Na1—O2iii | 2.389 (2) |
S1—O3 | 1.4408 (19) | Na1—O2iv | 2.476 (2) |
S1—O4 | 1.4396 (19) | Na1—O4v | 2.340 (2) |
O1—O1i | 1.479 (3) | Na1—O4vi | 2.596 (2) |
Na1—O3 | 2.376 (2) | Na1—Na1ii | 3.565 (2) |
O1—S1—O2 | 97.30 (11) | O2iii—Na1—Na1ii | 121.43 (7) |
O1—S1—O3 | 105.92 (11) | O2iv—Na1—Na1ii | 73.92 (6) |
O1—S1—O4 | 106.87 (11) | O4vi—Na1—Na1ii | 79.90 (6) |
O2—S1—O3 | 115.78 (12) | O4v—Na1—O3 | 103.99 (8) |
O2—S1—O4 | 115.65 (12) | O3ii—Na1—O3 | 82.92 (8) |
O3—S1—O4 | 113.08 (11) | O2iii—Na1—O3 | 153.31 (8) |
O1i—O1—S1 | 106.26 (17) | O2iv—Na1—O3 | 77.27 (7) |
O4v—Na1—O3ii | 154.76 (8) | O4vi—Na1—O3 | 85.88 (8) |
O4v—Na1—O2iii | 97.98 (8) | Na1ii—Na1—O3 | 41.50 (5) |
O3ii—Na1—O2iii | 83.62 (7) | Na1vii—O2—Na1iv | 102.44 (7) |
O4v—Na1—O2iv | 126.29 (8) | Na1vii—O2—S1 | 127.66 (11) |
O3ii—Na1—O2iv | 78.77 (7) | Na1iv—O2—S1 | 127.67 (11) |
O2iii—Na1—O2iv | 77.56 (7) | Na1—O3—Na1ii | 97.08 (8) |
O4v—Na1—O4vi | 77.36 (7) | Na1—O3—S1 | 128.52 (11) |
O3ii—Na1—O4vi | 79.00 (7) | Na1ii—O3—S1 | 134.38 (11) |
O2iii—Na1—O4vi | 113.94 (8) | Na1v—O4—Na1viii | 102.64 (7) |
O2iv—Na1—O4vi | 153.52 (7) | Na1v—O4—S1 | 137.82 (12) |
O4v—Na1—Na1ii | 139.91 (7) | Na1viii—O4—S1 | 117.76 (11) |
O3ii—Na1—Na1ii | 41.42 (5) |
Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) −x, −y+1, −z; (iii) x−1, y−1, z; (iv) −x+1, −y+1, −z; (v) −x+1, −y+1, −z+1; (vi) x−1, y, z; (vii) x+1, y+1, z; (viii) x+1, y, z. |
Acknowledgements
We thank Dr F. P. A. Fabbiani for her help during the data collection and Professor A. J. Blake for his help in preparing this manuscript. We also thank the EPSRC for funding both this project and DRA's Advanced Research Fellowship.
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