BING-1: a tin-oxalate-sodium-fluoride framework, Na₄Sn₄(C₂O₄)₃F₆

BING-1 [tetrasodium tetratin tris­(oxalate) hexafluoride] was synthesized solvothermally at 423 K and crystallized in the triclinic system, with the P space group. The asymmetric unit consists of two types of tin(II) centres, connected by oxalate groups. The Sn atoms are also bonded to fluoride ions, which bond the tin oxalate layers together via interlayer Na atoms, to define a three-dimensional framework.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• R factor = 0.034
• wR factor = 0.087
• Data-to-parameter ratio = 18.5

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          From the CIF: _chemical_formula_sum :C6 F6 Na4 O12 Sn4

General Notes



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          _chemical_formula_sum and _chemical_formula_moiety. This is
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          Atom count from _chemical_formula_sum:   C6 F6 Na4 O12 Sn4
          Atom count from _chemical_formula_moiety:C6 Na12 O12 Sn12


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S1. Comment

We are currently focusing on the solvothermal synthesis of layered and open-framework materials based on lower Group 14 metals. In particular, we are interested in non-traditional templating agents for the formation of anionic and cationic germanates and stannates. In the course of our work on the Sn–HF–H₂O–pyridine system, where the latter is the non-aqueous solvent, we have discovered a series of new metastable three-dimensional and lower dimensionality materials. We denote our structures as BING-n, where BING denotes State University of New York (SUNY) at Binghamton, and n denotes structure type.

Our structure is related to the series of tin oxalates recently reported by Cheetham and co-workers (Ayyappan et al., 1998; Natarajan et al., 1999). The latter are layered, where octahedral Sn atoms are three-connected in the plane of the layer by oxalate groups. The anionic layers are separated and charge-balanced by electrostatically bonded organic ammonium groups.

In the current work, we used a predominantly non-aqueous environment, where a small amount of water and hydrogen fluoride (50% aqueous) were added to a pyridine solvent. Sodium tetrafluoroborate was also added to the synthesis mixture, which is known to act as a mineralizer. Sodium and fluoride combined with tin oxalate to create the BING-1 three-dimensional framework (Fig. 1). The key feature of BING-1, which enables the formation of a framework, is the pentacoordinate Na1 and heptacoordinate Na2 atoms, which covalently bond to the fluorines and O atoms of the layers, and link the layers along the c axis.

There are two crystallographically unique tin centres, which are bonded to fluorines and O atoms on one side of the atoms (Fig. 2). The other side of the tin centres were in close proximity to other tins, and appear as bonds in Fig. 1. The distances, however, are on the order of 3.6 to 3.8 Å (Table 2), which is longer than those in metallic tin. The residual electron-density Fourier difference map could not resolve the nature of the tin–tin interaction.

Both Sn1 and Sn2 are four-coordinate with respect to fluorine and oxygen. Sn1 bonds to F1 and F2, as well as O1 and O2 of the C1—C1 oxalate group; the latter dimerizes the Sn1 to another Sn1. Sn2 bonds to one fluorine and three O atoms (Table 1). Two of these O atoms, O3 and O5, belong to one side of the C2—C3 oxalate group (torsion angles, Table 1). The third oxygen, O4, bonds to another oxalate group on the other side of Sn2, to define a tin oxalate chain that propogates along the a axis. The last oxgyen of the C2—C3 oxalate group, O6, bonds to two Na atoms [O6—Na1 2.419 (3) Å and O6—Na2 2.443 (3) Å]. The C—C distance of the oxalate groups [C1—C1 1.559 (8) Å and C2—C3 1.552 (5) Å] compares well with other metal oxalate structures (Belaj et al., 2000).

S2. Experimental

The reaction mixture consisted of pyridine, H₂0, HF, NaBF₄ and Sn(C₂O₄) in a molar ratio of 20:4:1:1:1. The pH of the starting mixture was aproximately 5.8. Solvothermal synthesis was conducted in a 23 ml capacity Teflon-lined Parr autoclave, at 423 K for 5 d. The BING-1 crystals were colourless plates and were manually separated for single-crystal X-ray analysis. Small black crystals were also present in the product as a minor side-product. The latter was identified, also by single-crystal X-ray analysis, as tin(II) oxide.

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and ATOMS (Dowty, 1999); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The crystallographic a projection of BING-1 highlights the tin oxalate fluoride layers, and the oxalate linkage of the tin centres (colour scheme: orange – Sn, yellow – Na, blue – F, green – C and red – O).
	Fig. 2. Displacement ellipsoids and labelling scheme for BING-1, shown at 50% probability levels. [Symmetry code: (i) 1 - x, -y, -z.]

tin(II)oxalate tetrasodium hexafluorate

Crystal data

Na4Sn4(C2O4)3F6	Z = 1
Mr = 944.78	F(000) = 430
Triclinic, P1	Dx = 3.514 Mg m^−3
a = 6.0283 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.7916 (6) Å	Cell parameters from 4605 reflections
c = 9.1191 (6) Å	θ = 4.8–61°
α = 69.486 (1)°	µ = 5.75 mm^−1
β = 81.508 (1)°	T = 293 K
γ = 83.017 (1)°	Prism, colorless
V = 446.41 (5) Å^3	0.15 × 0.10 × 0.08 mm

Data collection

Siemens SMART CCD diffractometer	2686 independent reflections
Radiation source: fine-focus sealed tube	2253 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ω scans	θmax = 30.6°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→8
Tmin = 0.465, Tmax = 0.631	k = −12→12
7096 measured reflections	l = −13→12

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.034	Secondary atom site location: difference Fourier map
wR(F^2) = 0.087	w = 1/[σ^2(Fo^2) + (0.0547P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max < 0.001
2686 reflections	Δρmax = 2.07 e Å^−3
145 parameters	Δρmin = −1.48 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
Na1	−0.2913 (3)	0.0444 (2)	−0.4217 (2)	0.0316 (4)
Na2	0.1397 (3)	0.2643 (2)	−0.3760 (2)	0.0272 (4)
Sn1	0.16908 (4)	−0.13839 (3)	−0.13383 (3)	0.02056 (9)
Sn2	0.16735 (5)	0.43093 (3)	−0.82016 (3)	0.02177 (10)
F1	0.3612 (4)	−0.0411 (3)	−0.3430 (3)	0.0309 (6)
F2	−0.0601 (4)	0.0434 (3)	−0.2572 (3)	0.0307 (6)
F3	0.1316 (5)	0.2346 (3)	−0.6173 (3)	0.0334 (6)
C1	0.4140 (7)	0.0761 (5)	−0.0139 (5)	0.0209 (8)
O1	0.2467 (5)	0.0761 (4)	−0.0830 (4)	0.0245 (6)
O2	0.4532 (6)	0.1848 (4)	0.0324 (4)	0.0340 (8)
C2	0.6026 (7)	0.5028 (5)	−0.7296 (5)	0.0199 (7)
O3	0.5433 (5)	0.4089 (4)	−0.7904 (4)	0.0298 (7)
O4	0.7991 (5)	0.5225 (4)	−0.7153 (4)	0.0265 (7)
C3	0.4118 (6)	0.6055 (5)	−0.6648 (5)	0.0187 (7)
O5	0.2124 (5)	0.5788 (4)	−0.6765 (4)	0.0259 (6)
O6	0.4600 (5)	0.7024 (4)	−0.6081 (4)	0.0234 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Na1	0.0268 (9)	0.0389 (11)	0.0365 (10)	0.0067 (8)	−0.0150 (8)	−0.0206 (9)
Na2	0.0237 (8)	0.0253 (9)	0.0347 (10)	−0.0040 (7)	−0.0055 (7)	−0.0111 (8)
Sn1	0.02303 (15)	0.01670 (15)	0.02039 (15)	−0.00257 (11)	−0.00571 (10)	−0.00269 (11)
Sn2	0.02411 (16)	0.01898 (15)	0.02294 (16)	−0.00104 (11)	−0.00900 (11)	−0.00565 (12)
F1	0.0356 (14)	0.0366 (15)	0.0188 (12)	−0.0098 (12)	−0.0003 (10)	−0.0063 (11)
F2	0.0301 (13)	0.0235 (13)	0.0360 (15)	0.0002 (11)	−0.0197 (11)	−0.0012 (11)
F3	0.0479 (16)	0.0207 (13)	0.0283 (14)	0.0021 (12)	−0.0110 (12)	−0.0029 (11)
C1	0.0208 (18)	0.0217 (19)	0.0207 (19)	0.0021 (15)	−0.0077 (15)	−0.0070 (16)
O1	0.0267 (15)	0.0196 (14)	0.0285 (16)	0.0016 (12)	−0.0122 (12)	−0.0070 (13)
O2	0.0323 (17)	0.0298 (17)	0.048 (2)	0.0049 (14)	−0.0183 (15)	−0.0209 (17)
C2	0.0193 (17)	0.0197 (18)	0.0200 (18)	0.0013 (14)	−0.0040 (14)	−0.0058 (15)
O3	0.0218 (14)	0.0314 (17)	0.045 (2)	0.0012 (13)	−0.0064 (13)	−0.0240 (16)
O4	0.0153 (13)	0.0307 (17)	0.0368 (18)	0.0025 (12)	−0.0055 (12)	−0.0160 (15)
C3	0.0168 (17)	0.0175 (18)	0.0200 (18)	0.0021 (14)	−0.0050 (14)	−0.0038 (15)
O5	0.0169 (13)	0.0289 (16)	0.0381 (18)	0.0004 (12)	−0.0079 (12)	−0.0179 (15)
O6	0.0210 (13)	0.0215 (15)	0.0314 (16)	0.0002 (11)	−0.0088 (12)	−0.0119 (13)

Geometric parameters (Å, º)

Na1—F2	2.190 (3)	Sn2—O4^i	2.443 (3)
Na1—F1^i	2.243 (3)	F1—Na1^vi	2.243 (3)
Na1—F1^ii	2.257 (3)	F1—Na1^ii	2.257 (3)
Na1—O6^iii	2.419 (3)	F3—Na1^ii	2.446 (3)
Na1—F3^ii	2.446 (3)	C1—O2	1.231 (5)
Na2—F2	2.260 (3)	C1—O1	1.265 (5)
Na2—F3	2.313 (3)	C1—C1^v	1.559 (8)
Na2—O4^iv	2.386 (4)	O2—Sn1^v	2.518 (3)
Na2—O6^iv	2.443 (3)	C2—O4	1.249 (5)
Na2—O5^iii	2.467 (3)	C2—O3	1.252 (5)
Na2—O1	2.729 (4)	C2—C3	1.552 (5)
Na2—F1	2.787 (3)	O4—Na2^iv	2.386 (4)
Sn1—F1	2.039 (3)	O4—Sn2^vi	2.443 (3)
Sn1—F2	2.095 (2)	C3—O6	1.221 (5)
Sn1—O1	2.209 (3)	C3—O5	1.279 (5)
Sn1—O2^v	2.518 (3)	O5—Na2^iii	2.467 (3)
Sn2—F3	2.045 (3)	O6—Na1^iii	2.419 (3)
Sn2—O5	2.206 (3)	O6—Na2^iv	2.443 (3)
Sn2—O3	2.299 (3)
Sn1···Sn2^ii	3.6304 (5)	Sn2···Sn2^viii	3.8563 (5)
Sn1···Sn2^vii	3.8637 (5)	Na2···Sn1	3.4535 (19)
F2—Na1—F1^i	123.02 (14)	O5—Sn2—O3	72.13 (11)
F2—Na1—F1^ii	151.69 (14)	F3—Sn2—O4^i	82.99 (11)
F1^i—Na1—F1^ii	83.31 (11)	O5—Sn2—O4^i	70.63 (10)
F2—Na1—O6^iii	86.26 (12)	O3—Sn2—O4^i	141.73 (11)
F1^i—Na1—O6^iii	84.98 (12)	Sn1—F1—Na1^vi	136.74 (14)
F1^ii—Na1—O6^iii	108.13 (13)	Sn1—F1—Na1^ii	125.32 (13)
F2—Na1—F3^ii	84.90 (11)	Na1^vi—F1—Na1^ii	96.69 (11)
F1^i—Na1—F3^ii	91.03 (12)	Sn1—F1—Na2	90.03 (10)
F1^ii—Na1—F3^ii	84.40 (11)	Na1^vi—F1—Na2	96.49 (11)
O6^iii—Na1—F3^ii	166.25 (14)	Na1^ii—F1—Na2	95.27 (12)
F2—Na2—F3	89.83 (12)	Sn1—F2—Na1	131.65 (14)
F2—Na2—O4^iv	130.33 (14)	Sn1—F2—Na2	104.88 (11)
F3—Na2—O4^iv	136.59 (14)	Na1—F2—Na2	106.82 (13)
F2—Na2—O6^iv	131.00 (13)	Sn2—F3—Na2	120.11 (13)
F3—Na2—O6^iv	99.65 (13)	Sn2—F3—Na1^ii	126.73 (14)
O4^iv—Na2—O6^iv	68.27 (11)	Na2—F3—Na1^ii	103.70 (12)
F2—Na2—O5^iii	85.20 (12)	O2—C1—O1	126.1 (4)
F3—Na2—O5^iii	107.04 (12)	O2—C1—C1^v	117.4 (4)
O4^iv—Na2—O5^iii	67.42 (10)	O1—C1—C1^v	116.5 (4)
O6^iv—Na2—O5^iii	135.04 (12)	O4—C2—O3	127.0 (4)
F2—Na2—O1	65.02 (10)	O4—C2—C3	116.5 (4)
F3—Na2—O1	137.95 (12)	O3—C2—C3	116.5 (3)
O4^iv—Na2—O1	81.79 (11)	O6—C3—O5	125.6 (4)
O6^iv—Na2—O1	76.84 (11)	O6—C3—C2	119.4 (3)
O5^iii—Na2—O1	103.88 (12)	O5—C3—C2	115.0 (3)
F2—Na2—F1	62.08 (10)	C1—O1—Sn1	123.0 (3)
F3—Na2—F1	76.03 (10)	C1—O1—Na2	130.1 (3)
O4^iv—Na2—F1	132.73 (12)	C1—O2—Sn1^v	113.1 (3)
O6^iv—Na2—F1	73.80 (10)	C2—O3—Sn2	116.0 (3)
O5^iii—Na2—F1	147.25 (12)	C2—O4—Na2^iv	118.8 (3)
O1—Na2—F1	62.63 (9)	C2—O4—Sn2^vi	132.8 (3)
F1—Sn1—F2	79.39 (11)	C3—O5—Sn2	118.9 (3)
F1—Sn1—O1	84.79 (11)	C3—O5—Na2^iii	126.9 (2)
F2—Sn1—O1	77.99 (10)	C3—O6—Na1^iii	136.2 (3)
F1—Sn1—O2^v	81.38 (12)	C3—O6—Na2^iv	116.3 (3)
F2—Sn1—O2^v	143.05 (11)	Sn1—O1—Na2	88.10 (10)
O1—Sn1—O2^v	69.06 (11)	Sn2—O5—Na2^iii	111.72 (12)
F3—Sn2—O5	88.56 (11)	Na1^iii—O6—Na2^iv	101.66 (12)
F3—Sn2—O3	87.59 (12)	Na2^iv—O4—Sn2^vi	106.53 (12)
O1—C1—C1^v—O2^v	−0.3 (6)	O4—C2—C3—O6	2.1 (6)
O3—C2—C3—O5	2.1 (6)

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