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In the title compound, [Na(C3H6O)3]n(I2)n, all non-H atoms are in special positions of the space group P63/mcm, with the Na atom in 2b, the I atom in 4c, the carbonyl O atom and the C atom attached to it both in 6g, and the methyl C atom in 12k. The H atoms of the rotationally disordered methyl groups are in 24l general positions but with occupancies of 0.5, because they occur in two sets related by a crystallographic mirror plane. Infinite chains are created by face-sharing octahedral Na-coordination polyhedra, with Na—O and Na...Na distances of 2.439 (5) and 3.2237 (4) Å, respectively. I atoms form infinite linear chains, in which the I-atom separation is 3.2237 (4) Å.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103006395/fg1688sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103006395/fg1688Isup2.hkl
Contains datablock I

CCDC reference: 214147

Comment top

The preliminary information as to the nature of the title compound, (I), was no more than that it probably contained Na and I (from the circumstances under which it was obtained) and the solvate acetone (because after ready decomposition on exposure to the atmosphere it could be reconstituted by recrystallization from that solvent). A search based purely on cell dimensions using the CSEAR component of the Crystal Structure Search and Retrieval system (CSSR) of the Chemical Database Service (CDS) of the EPSRC at Daresbury (Fletcher et al., 1966) suggested close similarity to the structure of catena-[tris(µ2-dimethylformamide-O,O)]sodium iodide, (II), (Gobillon et al., 1962; Batsanov & Struchkov, 1994). The assumption of the presence of Na and I in (I) and the same hexagonal space group (P-62c) as (II) led ultimately to the successful solution and refinement of the structure of (I), which is reported here.

The coordination of the Na atom in (I) is shown in Fig. 1, along with the labelling scheme (with the exception of atom I1, which is not present in this figure). The coordination of the Na atom is determined by the −3 m site symmetry and is octahedral in nature, with six identical Na—O distances [2.439 (5) Å] and all trans O—Na—O angles exactly 180°. The octahedron is elongated by 16% in the c direction, as estimated by the increase relative to the ideal value of the perpendicular distance of Na from the shared faces of the coordination polyhedron, and as shown by the presence of two distinct values for the cis O—Na—O angles [81.08 (17) and 98.82 (17)°] and the lengths of the O—O octahedron edges [3.170 (13) Å on the shared faces of the octahedron and 3.707 (4) Å otherwise; Table 1]. The face sharing of the Na-coordination polyhedra, brought about by the µ2 bridging function of the carbonyl O atoms, results in the formation of infinite chains, as shown in Fig. 2, propagated in the c direction, with Na at 0,0,0 and 0,0,1/2.

The acetone solvate molecule is not well determined but is clearly recognizable in terms of its bond lengths and angles (Table 1). The molecule as a whole, excluding the methyl H atoms, lies on a crystallographic mirror plane parallel to c. The methyl groups are rotationally disordered between two mirror-plane-related arrangements, and the occupancies of the H atoms are therefore 1/2, while the sites of the C atoms to which they are attached are fully occupied.

The I atoms, of which there are four in the unit cell, occur in two infinite linear rows (2/3,1/3,z and 1/3,2/3,z), also propagated in the c direction, with I at z = 1/4 and 3/4 in both cases. The I—I separation, which is identical to the Na—Na separation in its row, is c/2 or 3.2237 (4) Å. The relative disposition of the rows of Na polyhedra and linear In chains is shown in Fig. 3.

The cell contains two Na and four I atoms, each species being in a symmetry-related set, and from charge balance considerations each I atom must, on average, carry a charge of −0.5. This could be achieved in many ways, of which perhaps the most likely are as follows: Neutral I and I anions may simply alternate along the length of the rows. Again there could be a mixture of I and In ions, with, for n odd and greater than 1, mono- and polyiodide species in the ratio n-2:1. Finally, taking into account the fact that the I atoms are related by symmetry and that the I—I separation of 3.2237 (4) Å within the chains, while greater than twice the normal covalent radius of I (2.80 Å), is much less than twice the van der Waals radius (3.96 Å) (values for radii taken from PLATON; Spek, 2003) allows the possibility of weak I—I bonds or at least charge transfer along what can now be regarded as multiply negatively charged polyiodide chains of infinite length.

The structural relationship between (I) and the published structure of (II) is in fact more distant, in several respects, than first anticipated, although a general similarity can be observed in figures in the form of Fig. 3, shown here for (I). They differ [properties for (II) in square brackets] in: space group, P63/mcm [P-62c]; Na coordination, octahedral [in the form of a trigonal prism]; the nature and orientation of the planar solvate molecules, acetone oriented parallel to c [DMF perpendicular to c] and finally the I—I separation, c/2 [cell translation in the direction of c] and hence the nature of I in their chains, infinite polyiodide [independent I anions]. There is some evidence suggesting that the difference in the type of iodide anion present in the two structures may be more apparent than real. In reporting the cell, space group and R factor (0.1390) corresponding to Cambridge Structural Database (Allen, 2002) entry NAIDMF01 (Batsanov & Struchkov, 1994), the CSSR comments that the 'I atoms (are) disordered over two sites'. This alone prompts consideration of the possibility that in this structure of (II), I is present in a greater amount than originally thought and may exist in an infinite polyiodide form similar to that described here for (I). Indeed, in the early stages of the refinement of (I) based on the structure of (II), R values very similar to and actually slightly better than that achieved for (II) by Batsanov & Struchkov (1994) were obtained for the isolated I model in space group P-62c. It was only upon introducing a second I atom, c/2 distant from that of the original model, to account for residual electron density of ~27 eÅ−3, that much improved refinement proved possible. The introduction of additional I into the Batsanov & Struchkov (1994) structure need not bring about a change in space group, which would in any case be difficult if the nature of the Na coordination and orientation of the dimethylformamide solvate molecules in (II) were to remain unchanged.

Experimental top

Crystalline (I) was obtained in place of the desired product (I3SnCH2CH2CO2Me) on leaving a solution obtained by the addition of a saturated solution of NaI in acetone (100 ml) to a solution of HCl, SnCl2 and H2CCHCO2Me (0.1 mol each) in diethyl ether (45 ml) exposed to air overnight. Further exposure of the lustrous dark crystalline solid to air overnight resulted in the formation of a dark grey powder, which recovered its crystalline form on recrystallization from acetone. The crystalline material was stable for weeks when stored in closed vessels with a little acetone.

Refinement top

Intensity data were collected for a full sphere of reflections on the basis of a C-centred orthorhombic cell corresponding to the primitive hexagonal cell noted above and reindexed accordingly. The heavy-atom method as implemented in SHELXS86 (Sheldrick, 1986) provided initial positions for Na and I, assuming equal numbers of Na and I atoms and the space group P-62c. Subsequent difference sytheses provided features identifiable as a representative acetone solvate molecule. As noted above this model did refine but only to an R value in excess of 0.10, with a large (~27 eÅ−3) residual electron density and application of constraints to most of the coordinates of the non-H atoms of the acetone molecule. Refinement improved dramatically with the addition of a second I atom at the site of the residual electron density. At this point, the PLATON (Spek, 2003) ADDSYM test (for additional/missing crystallographic symmetry) was applied, leading to the adoption of the space group P63/mcm, in which the refinement was completed. In the final stages of refinement, the H atoms of the methyl groups of the acetone molecule were introduced in calculated positions (with C—H distances of 0.98 Å and, taking account of the rotational disorder of the methyl groups over two arrangements related by a crystallographic mirror plane, occupancies of 1/2) and were refined using a riding model with Uiso equal to 1.5Ueq of the parent C atom. The refinement program (SHELXL97) continually recommended correction for extinction. This was investigated but not retained in the final refinement because, although the correction did indeed improve the R values, it also had the effect of promoting clearly erroneous residual electron density (~1.6 eÅ−3) mid-way between the Na atoms. In the absence of any form of chemical elemental analysis, several attempts were made to incorporate Sn atoms into the structure, but all of these proved unsuccessful.

Computing details top

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. The coordination of Na in (I). Non-H atoms are shown as displacement ellipsoids at the 50% probability level, and H atoms have been omitted for clarity. Dashed lines indicate the O—O edges of the shared faces of the coordination octahedron. [Symmetry codes: (i) −y,x-y,z; (ii) −x + y,-x,z; (iii) x,y,1/2 − z; (iv) −y,x-y,1/2 − z; (v) −x + y,-x,1/2 − z; (vi) −y,-x,z − 1/2; (vii) x,x-y,z − 1/2; (viii) −x + y,y,z − 1/2; (ix) −y,-x,-z; (x) x,x-y,-z; (xi) −x + y,y,-z.
[Figure 2] Fig. 2. A portion of a chain of face-sharing Na coordination polyhedra in (I). The representation, including the symmetry codes where given, is the same as for Fig. 1, but only selected atoms are labelled.
[Figure 3] Fig. 3. The unit cell of (I), viewed approximately along c. The representation is the same as for Fig. 2 except that symmetry codes are not given.
Catena-(sodium trisacetone solvate) polyiodide top
Crystal data top
[Na(C3H6O)3](I2)Dx = 1.957 Mg m3
Mr = 451.02Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P63/mcmCell parameters from 14507 reflections
a = 11.7086 (13) Åθ = 2.9–27.5°
c = 6.4475 (8) ŵ = 4.13 mm1
V = 765.48 (15) Å3T = 120 K
Z = 2Plate, brown
F(000) = 4260.50 × 0.22 × 0.04 mm
Data collection top
Enraf Nonius KappaCCD area detector
diffractometer
352 independent reflections
Radiation source: Enraf Nonius FR591 rotating anode261 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.102
Detector resolution: 9.091 pixels mm-1θmax = 27.5°, θmin = 3.5°
ϕ and ω scansh = 1415
Absorption correction: multi-scan
(SORTAV; Blessing, 1995,1997)
k = 1514
Tmin = 0.150, Tmax = 0.389l = 87
6540 measured reflections
Refinement top
Refinement on F2Primary atom site location: heavy-atom method
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.047Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.133H-atom parameters constrained
S = 1.09 w = 1/[σ2(Fo2) + (0.0763P)2 + 1.5007P]
where P = (Fo2 + 2Fc2)/3
352 reflections(Δ/σ)max < 0.001
20 parametersΔρmax = 0.57 e Å3
0 restraintsΔρmin = 1.94 e Å3
Crystal data top
[Na(C3H6O)3](I2)Z = 2
Mr = 451.02Mo Kα radiation
Hexagonal, P63/mcmµ = 4.13 mm1
a = 11.7086 (13) ÅT = 120 K
c = 6.4475 (8) Å0.50 × 0.22 × 0.04 mm
V = 765.48 (15) Å3
Data collection top
Enraf Nonius KappaCCD area detector
diffractometer
352 independent reflections
Absorption correction: multi-scan
(SORTAV; Blessing, 1995,1997)
261 reflections with I > 2σ(I)
Tmin = 0.150, Tmax = 0.389Rint = 0.102
6540 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0470 restraints
wR(F2) = 0.133H-atom parameters constrained
S = 1.09Δρmax = 0.57 e Å3
352 reflectionsΔρmin = 1.94 e Å3
20 parameters
Special details top

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 (Å2) top
xyzUiso*/UeqOcc. (<1)
Na10.00000.00000.00000.0495 (18)
I10.66670.33330.25000.0503 (4)
O10.1563 (6)0.1563 (6)0.25000.061 (2)
C10.2597 (8)0.2597 (8)0.25000.041 (2)
C20.3234 (8)0.3234 (8)0.0551 (13)0.056 (2)
H3A0.27950.26240.06030.084*0.50
H3B0.41640.34750.05930.084*0.50
H3C0.31690.40300.03560.084*0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Na10.042 (3)0.042 (3)0.064 (4)0.0211 (13)0.0000.000
I10.0331 (4)0.0331 (4)0.0846 (8)0.0166 (2)0.0000.000
O10.041 (3)0.041 (3)0.093 (5)0.015 (4)0.0000.000
C10.043 (4)0.043 (4)0.048 (5)0.030 (5)0.0000.000
C20.067 (4)0.067 (4)0.052 (4)0.046 (5)0.008 (3)0.008 (3)
Geometric parameters (Å, º) top
Na1—O12.439 (5)O1—Na1vi2.439 (5)
Na1—O1i2.439 (5)C1—C2vi1.461 (10)
Na1—O1ii2.439 (5)C1—C21.461 (10)
Na1—O1iii2.439 (5)C2—H3A0.9800
Na1—O1iv2.439 (5)C2—H3B0.9800
Na1—O1v2.439 (5)C2—H3C0.9800
Na1—Na1vi3.2237 (4)O1—O1iii3.170 (13)
Na1—Na1vii3.2237 (4)O1—O1iv3.707 (4)
O1—C11.210 (11)I1—I1viii3.2237 (4)
O1—Na1—O1i180.0O1v—Na1—Na1vi48.63 (11)
O1—Na1—O1ii98.92 (17)O1—Na1—Na1vii131.37 (11)
O1i—Na1—O1ii81.08 (17)O1i—Na1—Na1vii48.63 (11)
O1—Na1—O1iii81.08 (17)O1ii—Na1—Na1vii48.63 (11)
O1i—Na1—O1iii98.92 (17)O1iii—Na1—Na1vii131.37 (11)
O1ii—Na1—O1iii180.0O1iv—Na1—Na1vii48.63 (11)
O1—Na1—O1iv98.92 (17)O1v—Na1—Na1vii131.37 (11)
O1i—Na1—O1iv81.08 (17)Na1vi—Na1—Na1vii180.0
O1ii—Na1—O1iv81.08 (17)C1—O1—Na1138.63 (11)
O1iii—Na1—O1iv98.92 (17)C1—O1—Na1vi138.63 (11)
O1—Na1—O1v81.08 (17)Na1—O1—Na1vi82.7 (2)
O1i—Na1—O1v98.92 (17)O1—C1—C2vi120.7 (5)
O1ii—Na1—O1v98.92 (17)O1—C1—C2120.7 (5)
O1iii—Na1—O1v81.08 (17)C2vi—C1—C2118.6 (10)
O1iv—Na1—O1v180.0C1—C2—H3A109.5
O1—Na1—Na1vi48.63 (11)C1—C2—H3B109.5
O1i—Na1—Na1vi131.37 (11)H3A—C2—H3B109.5
O1ii—Na1—Na1vi131.37 (11)C1—C2—H3C109.5
O1iii—Na1—Na1vi48.63 (11)H3A—C2—H3C109.5
O1iv—Na1—Na1vi131.37 (11)H3B—C2—H3C109.5
Symmetry codes: (i) x, y, z; (ii) xy, x, z; (iii) x+y, x, z; (iv) y, x+y, z; (v) y, xy, z; (vi) x, y, z+1/2; (vii) x, y, z1/2; (viii) x, xy, z+1/2.

Experimental details

Crystal data
Chemical formula[Na(C3H6O)3](I2)
Mr451.02
Crystal system, space groupHexagonal, P63/mcm
Temperature (K)120
a, c (Å)11.7086 (13), 6.4475 (8)
V3)765.48 (15)
Z2
Radiation typeMo Kα
µ (mm1)4.13
Crystal size (mm)0.50 × 0.22 × 0.04
Data collection
DiffractometerEnraf Nonius KappaCCD area detector
diffractometer
Absorption correctionMulti-scan
(SORTAV; Blessing, 1995,1997)
Tmin, Tmax0.150, 0.389
No. of measured, independent and
observed [I > 2σ(I)] reflections
6540, 352, 261
Rint0.102
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.047, 0.133, 1.09
No. of reflections352
No. of parameters20
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.57, 1.94

Computer programs: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998), DENZO and COLLECT, SHELXS86 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), SHELXL97 and PLATON (Spek, 2003).

Selected geometric parameters (Å, º) top
Na1—O12.439 (5)O1—O1ii3.170 (13)
Na1—Na1i3.2237 (4)O1—O1iii3.707 (4)
O1—C11.210 (11)I1—I1iv3.2237 (4)
C1—C21.461 (10)
O1—Na1—O1v180.0Na1—O1—Na1i82.7 (2)
O1—Na1—O1ii81.08 (17)O1—C1—C2120.7 (5)
O1—Na1—O1iii98.92 (17)C2i—C1—C2118.6 (10)
C1—O1—Na1138.63 (11)
Symmetry codes: (i) x, y, z+1/2; (ii) x+y, x, z; (iii) y, x+y, z; (iv) x, xy, z+1/2; (v) x, y, z.
 

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