2,2'-Bi[benzo[b]thio­phene]: an unexpected isolation of the benzo[b]thio­phene dimer

The crystal structure of 2,2'-bi[benzo[b]thio­phene], C₁₆H₁₀S₂, at 173 K has triclinic (P) symmetry. It is of inter­est with respect to its apparent mode of synthesis, as it is a by-product of a Stille cross-coupling reaction in which it was not explictly detected by spectroscopic methods. It was upon crystal structure analysis of a specimen isolated from the mother liquor that this reaction was determined to give rise to the title compound, which is a dimer arising from the starting material. Two independent half-mol­ecules of this dimer comprise the asymmetric unit, and the full mol­ecules are generated via inversion centers. Both mol­ecules in the unit cell exhibit ring disorder, and they are essentially identical because of their rigidity and planarity.

S1. Introduction

This account of the structural chemistry of 2,2'-bi[benzo[b]thio­phene], (I), is of a rather serendipitous nature. The original intent was to utilize (benzo[b]thio­phen-2-yl)tri­butyl­stannane in a Stille cross-coupling reaction (Espinet & Echavarren, 2004) with 2-chloro-3-methyl­pyridine to yield 2-(benzo[b]thio­phen-2-yl)-3-methyl­pyridine. Surprisingly, analysis of the crystals that were grown and harvested after the reaction did not support the structure of the desired compound, but rather that of (I), which is a by-product formed during the cross-coupling reaction. The generalized cross-coupling reaction involves a halogenated sp²-hybridized species R reacting with an sp²-hybridized species R' that is bonded to a sterically hindered metal core. In order for homodimer (I) to form, the species benzo[b]thio­phene–Pd–benzo[b]thio­phene must have formed during the Pd^II to Pd⁰ catalyst-reduction step of the cross-coupling. Reductive elimination would then give rise to the observed dimer. Although only a minor impurity in the isolated desired product, by-product (I) was the sole species identified during single-crystal structure determination. Whilst impurities from cross-coupling reactions can occur, this study demonstrates the importance of reconciling the crystal structures from cross-coupling reactions with the identity of the material in the bulk product.

S2. Experimental

S2.1. Synthesis and crystallization

Compound (I) was synthesized using a one-step procedure starting from (benzo[b]thio­phen-2-yl)tri­butyl­stannane and dichloridobis(tri­phenyl­phosphane)palladium(II). 2-Chloro-3-methyl­pyridine, while present in the reaction mixture, did not participate in the dimerization reaction.

After completion of the cross-coupling reaction as determined by high-performance liquid chromatography mass spectroscopy (HPLC–MS), the reaction mixture was adsorbed onto silica gel and subjected to flash chromatography. The isolated material was re-subjected to silica-gel flash chromatography to remove residual undesired by-products (e.g. Bu₃SnX residues). A portion of the purified material (48 mg, >95% purity by HPLC–MS and ¹H NMR) was dissolved in diiso­propyl ether (1.0 ml) and the resulting solution was filtered through a 0.45 µm Teflon filter into an uncapped small vial, which was then placed into a large vial containing hexane (4.0 ml). Vapour diffusion led to the crystallization of a cluster of solid, of which one crystal appeared to be suitable for single-crystal X-ray diffraction analysis. Although the solid was colourless, the selected crystal was clearer than its surroundings.

With regard to the ¹H NMR spectroscopic data, a very small aberrant singlet was noted in the aromatic region, and if this tiny peak is assumed to be that of a single proton of compound (I), then (I) was present at less than 3 mol% in solution, perhaps even as low as 2 mol%. The elusiveness of (I) in solution is further established by its total lack of appearance in the HPLC–MS data. However, once the unexpected X-ray crystal structure was obtained, re-evaluation of the bulk material in a deliberate search for this by-product by thin-layer chromatography (TLC) revealed traces of it.

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. C-bound H atoms were placed in calculated positions and constrained as riding atoms, with C—H = 0.95 Å and U_iso(H) = 1.2U_eq(C).

The additional atoms arising from the disorder of (I) were located from Fourier difference maps. The disorder was modelled by refining the occupancies of the C and S atoms involved in the disorder. The geometries from the refinement were found to be reasonable without the application of constraints.

S3. Results and discussion

The crystal structure of (I) obtained from the present structure determination was found to contain two independent half-molecules of (I) in the asymmetric unit (Fig. 1). The proximity of each half-molecule to an inversion centre results in the generation of the rest of the molecule by symmetry. The C—C bond distances between the two halves of each molecule across the inversion centre are 1.448 (3) and 1.447 (3) Å, respectively, suggestive of the fact that this C—C bond has double-bond or aromatic character, a conclusion which is reinforced by the planarity of the molecules.

During the course of the refinement, it became clear that there was disorder of the benzo[b]thio­phene ring. The S atom was found to be disordered with the C atom at the 7-position, meaning that the entire molecule is flipped 180° over its long axis. The centre of inversion makes it impossible for the disorder to arise from the presence of molecules with the syn geometry because the inversion centre necessitates that a half-molecule of (I) generates the other half of the molecule with the opposing conformation. As there are two independent half-molecules of (I) in the asymmetric unit, designating one molecule as A and the other as B, molecule A is 72% in its major configuration and 28% in its minor, whereas molecule B is 61% in its major configuration and 39% in its minor.

Initial assessment of the crystal structure of (I) suggested that there were two independent benzo[b]thio­phene rings in the asymmetric unit. This would have been suggestive that they had become disengaged from the stannane starting material during the course of the reaction. However, their proximity to an inversion centre imposes a symmetry equivalent that is 1.448 Å away from the C atom at the 8-position, which could only be explained if dimerization had occured (Fig. 1). The C—C bond length is similar to that observed for 2,2'-bi­thio­phene, which was reported to be 1.448 Å (Ali-Adib et al., 1984).

Owing to the planarity of each half-molecule and their relationship with the inversion centre, the conformations of both independent molecules of (I) are essentially identical. The five- and six-membered rings are both planar, which was also reported for the crystal structure of the monomer benzo[b]thio­phene (Pelletier & Brisse, 1994; Chaloner et al., 1994). In (I), the S—C—C—S torsion angle that separates the two halves of each molecule is 180° (as depicted in Scheme 2). A 0° torsion angle occurs when the S atoms are syn to one another and a 180° torsion angle occurs when they are anti to each other.

The geometric results of the crystal structure determination complement the computational study performed by Hayashi & Higuchi (2009). In their work, the calculations predicted that (I) would have two minima in its energy landscape. The global minimum is the anti conformation at an S—C—C—S torsion angle of 157°. A local minimum exists at 44°, which represents an offset syn conformation. A fully planar syn conformation at an S—C—C—S torsion angle of 0° is calculated to be an energy maximum. Neither syn conformation is observed in the present crystal structure.

The molecular packing arrangement of (I) shows that the molecules do not have strong inter­molecular contacts with each other (Fig. 2). The centroid-to-centroid distance between the closest neighbouring benzene rings of (I) is 4.72 Å, and noncovalent inter­actions such as π–π are not present in this crystal structure, although possible C—H···π contacts may be identified (e.g. C5B—H5BA to a neighbouring inter­molecular π-system and C5A—H5AA to a neighbouring inter­molecular π-system). Without stronger inter­actions to lock the orientations of the molecules in the solid state, the existence of disorder for this planar and symmetric molecule seems sensible.

In conclusion, while the cross-coupling reaction of (benzo[b]thio­phen-2-yl)tri­butyl­stannane and 2-chloro-3-methyl­pyridine using di­chloro­bis­(tri­phenyl­phosphine)palladium (II) as the pre-catalyst resulted in almost exclusively the desired compound as analysed by spectroscopic methods (>95%), dimer (I) formed in sufficient amounts to crystallize and become the dominant species in the specimen as analysed by single-crystal X-ray diffraction. Because the prospect of dimerization is general to cross-coupling reactions, the results of single-crystal analysis of a specimen arising from such a reaction mixture should be carefully compared with spectroscopic data in order to determine how representative the crystal structure is of the surrounding solid product.

Related literature

For related literature, see: Ali-Adib, Rawas & Sutherland (1984); Chaloner et al. (1994); Espinet & Echavarren (2004); Hayashi & Higuchi (2009); Pelletier & Brisse (1994).

Computing details

Data collection: COSMO (Bruker, 2009); cell refinement: APEX2 (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Fig. 1. The asymmetric unit of (I), showing the two molecules in the unit cell Displacement ellipsoids are drawn at the 50% probability level. [Please provide a revised version with a white/transparent background, and please also include enough atom labels to enable unique identification of all atoms, including symmetry codes as necessary.]

Fig. 2. A packing diagram for (I), viewed along the c axis. H atoms have been omitted for clarity. Only one configuration of the molecules is shown.

2,2'-Bi[benzo[b]thiophene]

Crystal data

C16H10S2	Z = 2
Mr = 266.36	F(000) = 276
Triclinic, P1	Dx = 1.450 Mg m^−3
Hall symbol: -P 1	Cu Kα radiation, λ = 1.54178 Å
a = 5.8415 (1) Å	Cell parameters from 5762 reflections
b = 7.6197 (1) Å	θ = 3.2–72.2°
c = 14.2782 (2) Å	µ = 3.73 mm^−1
α = 76.286 (1)°	T = 173 K
β = 81.118 (1)°	Plate, colourless
γ = 88.699 (1)°	0.36 × 0.32 × 0.04 mm
V = 609.94 (2) Å^3

Data collection

Bruker APEXII CCD area-detector diffractometer	2313 independent reflections
Radiation source: fine-focus sealed tube	2129 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.036
Detector resolution: 836.6 pixels mm^-1	θmax = 72.2°, θmin = 3.2°
ω and/f 0.5° scans	h = −5→7
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −9→9
Tmin = 0.348, Tmax = 0.853	l = −16→17
8960 measured reflections

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.112	H-atom parameters constrained
S = 0.93	w = 1/[σ^2(Fo^2) + (0.070P)^2 + 0.3344P] where P = (Fo^2 + 2Fc^2)/3
2313 reflections	(Δ/σ)max < 0.001
177 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

Special details

Experimental. Data were collected using a Bruker CCD (charge-coupled device)-based diffractometer equipped with an Oxford low-temperature apparatus operating at 173 K. A suitable crystal was chosen and mounted on a nylon loop using mineral oil for copper radiation. Data were measured using ω and ϕ scans of 1.0° per frame for 30 s. The total number of images was based on results from the program COSMO, where redundancy was expected to be 4 and completeness to 0.83 to 100%. Cell parameters were retrieved using APEX2 software and refined using SAINT on all observed reflections. Data reduction was performed using the SAINT software, which corrects for Lp and decay. Scaling and absorption corrections were performed by the SADABS program. The structures were solved by the direct method using the SHELX90 program and refined by the least-squares method on F2 using SHELXL93, incorporated in SHELXTL version 6.1.

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.

The following atoms were constrained to having the same thermal values. eadp c7b c7bb eadp s1b s1bb eadp c7a c7ab eadp s1a s1ab

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1A	−0.21435 (15)	0.36901 (11)	0.63774 (6)	0.0264 (2)	0.6131 (12)
C7A	0.1790 (7)	0.5360 (5)	0.5940 (3)	0.0281 (8)	0.6131 (12)
H7AB	0.3134	0.5998	0.5566	0.034*	0.6131 (12)
S1AB	0.2585 (3)	0.5707 (2)	0.58009 (12)	0.0264 (2)	0.3869 (12)
C7AB	−0.1321 (10)	0.4023 (8)	0.6306 (5)	0.0281 (8)	0.3869 (12)
H7AA	−0.2717	0.3466	0.6251	0.034*	0.3869 (12)
C1A	−0.0686 (3)	0.3982 (2)	0.72842 (13)	0.0297 (4)
C2A	−0.1582 (3)	0.3364 (2)	0.82716 (14)	0.0354 (4)
H2AA	−0.3037	0.2750	0.8465	0.042*
C3A	−0.0319 (3)	0.3661 (3)	0.89592 (14)	0.0387 (4)
H3AA	−0.0921	0.3259	0.9633	0.046*
C4A	0.1830 (3)	0.4543 (2)	0.86815 (14)	0.0375 (4)
H4AA	0.2681	0.4722	0.9168	0.045*
C5A	0.2734 (3)	0.5157 (2)	0.77119 (14)	0.0339 (4)
H5AA	0.4201	0.5755	0.7528	0.041*
C6A	0.1472 (3)	0.4891 (2)	0.70008 (13)	0.0287 (4)
C8A	0.0106 (3)	0.4855 (2)	0.55109 (12)	0.0238 (3)
S1B	0.24675 (11)	0.11677 (9)	0.40529 (5)	0.0273 (2)	0.7234 (16)
C7B	0.6423 (7)	−0.0348 (4)	0.3769 (2)	0.0284 (7)	0.7234 (16)
H7BA	0.7830	−0.0949	0.3886	0.034*	0.7234 (16)
S1BB	0.7176 (4)	−0.0595 (3)	0.37345 (17)	0.0273 (2)	0.2766 (16)
C7BB	0.3217 (14)	0.0846 (11)	0.3997 (7)	0.0284 (7)	0.2766 (16)
H7BB	0.1844	0.1269	0.4319	0.034*	0.2766 (16)
C1B	0.3556 (3)	0.0977 (2)	0.29021 (13)	0.0277 (4)
C2B	0.2467 (3)	0.1641 (2)	0.20905 (15)	0.0374 (4)
H2BA	0.0999	0.2199	0.2155	0.045*
C3B	0.3569 (4)	0.1470 (3)	0.11913 (15)	0.0449 (5)
H3BA	0.2853	0.1926	0.0630	0.054*
C4B	0.5712 (4)	0.0642 (3)	0.10913 (14)	0.0437 (5)
H4BA	0.6437	0.0542	0.0463	0.052*
C5B	0.6794 (3)	−0.0034 (2)	0.18894 (14)	0.0362 (4)
H5BA	0.8248	−0.0611	0.1817	0.043*
C6B	0.5729 (3)	0.0141 (2)	0.28060 (13)	0.0276 (4)
C8B	0.4907 (3)	0.0120 (2)	0.44888 (12)	0.0244 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1A	0.0193 (4)	0.0274 (4)	0.0304 (4)	−0.0038 (3)	−0.0013 (3)	−0.0039 (3)
C7A	0.0174 (16)	0.0246 (16)	0.0399 (17)	−0.0006 (13)	0.0000 (15)	−0.0056 (12)
S1AB	0.0193 (4)	0.0274 (4)	0.0304 (4)	−0.0038 (3)	−0.0013 (3)	−0.0039 (3)
C7AB	0.0174 (16)	0.0246 (16)	0.0399 (17)	−0.0006 (13)	0.0000 (15)	−0.0056 (12)
C1A	0.0265 (8)	0.0232 (8)	0.0403 (10)	0.0048 (7)	−0.0077 (7)	−0.0084 (7)
C2A	0.0266 (8)	0.0290 (9)	0.0450 (10)	0.0008 (7)	0.0030 (7)	−0.0033 (8)
C3A	0.0438 (10)	0.0350 (9)	0.0327 (9)	0.0082 (8)	0.0019 (8)	−0.0046 (8)
C4A	0.0432 (10)	0.0345 (9)	0.0402 (10)	0.0085 (8)	−0.0150 (8)	−0.0144 (8)
C5A	0.0264 (8)	0.0264 (8)	0.0490 (11)	0.0006 (7)	−0.0054 (7)	−0.0094 (8)
C6A	0.0271 (8)	0.0205 (7)	0.0354 (9)	0.0049 (6)	0.0003 (7)	−0.0043 (7)
C8A	0.0186 (7)	0.0174 (7)	0.0339 (9)	0.0020 (6)	−0.0012 (6)	−0.0047 (6)
S1B	0.0215 (4)	0.0283 (4)	0.0325 (3)	0.0069 (2)	−0.0049 (3)	−0.0078 (2)
C7B	0.0210 (14)	0.0254 (14)	0.0402 (15)	0.0067 (12)	−0.0076 (13)	−0.0096 (10)
S1BB	0.0215 (4)	0.0283 (4)	0.0325 (3)	0.0069 (2)	−0.0049 (3)	−0.0078 (2)
C7BB	0.0210 (14)	0.0254 (14)	0.0402 (15)	0.0067 (12)	−0.0076 (13)	−0.0096 (10)
C1B	0.0246 (8)	0.0210 (7)	0.0374 (9)	−0.0013 (6)	−0.0034 (7)	−0.0075 (6)
C2B	0.0327 (9)	0.0272 (9)	0.0544 (12)	0.0045 (7)	−0.0181 (8)	−0.0072 (8)
C3B	0.0622 (13)	0.0337 (10)	0.0405 (11)	−0.0074 (9)	−0.0253 (10)	0.0000 (8)
C4B	0.0542 (12)	0.0448 (11)	0.0319 (9)	−0.0169 (10)	0.0018 (8)	−0.0125 (8)
C5B	0.0305 (9)	0.0346 (9)	0.0453 (11)	−0.0035 (7)	0.0017 (7)	−0.0176 (8)
C6B	0.0246 (8)	0.0211 (7)	0.0375 (9)	−0.0016 (6)	−0.0063 (7)	−0.0066 (7)
C8B	0.0202 (7)	0.0202 (7)	0.0331 (9)	0.0004 (6)	−0.0046 (6)	−0.0065 (6)

Geometric parameters (Å, º)

S1A—C1A	1.7136 (19)	S1B—C1B	1.7064 (18)
S1A—C8A	1.7536 (18)	S1B—C8B	1.7442 (17)
C7A—C8A	1.344 (4)	C7B—C8B	1.359 (4)
C7A—C6A	1.454 (4)	C7B—C6B	1.455 (4)
C7A—H7AB	0.9500	C7B—H7BA	0.9500
S1AB—C6A	1.707 (2)	S1BB—C6B	1.661 (3)
S1AB—C8A	1.745 (2)	S1BB—C8B	1.737 (3)
C7AB—C8A	1.332 (6)	C7BB—C8B	1.334 (9)
C7AB—C1A	1.493 (7)	C7BB—C1B	1.525 (9)
C7AB—H7AA	0.9500	C7BB—H7BB	0.9500
C1A—C2A	1.397 (3)	C1B—C2B	1.392 (3)
C1A—C6A	1.408 (2)	C1B—C6B	1.410 (2)
C2A—C3A	1.377 (3)	C2B—C3B	1.378 (3)
C2A—H2AA	0.9500	C2B—H2BA	0.9500
C3A—C4A	1.394 (3)	C3B—C4B	1.392 (3)
C3A—H3AA	0.9500	C3B—H3BA	0.9500
C4A—C5A	1.376 (3)	C4B—C5B	1.376 (3)
C4A—H4AA	0.9500	C4B—H4BA	0.9500
C5A—C6A	1.397 (3)	C5B—C6B	1.395 (3)
C5A—H5AA	0.9500	C5B—H5BA	0.9500
C8A—C8A^i	1.447 (3)	C8B—C8B^ii	1.448 (3)
C1A—S1A—C8A	89.14 (9)	C1B—S1B—C8B	90.53 (8)
C8A—C7A—C6A	117.3 (3)	C8B—C7B—C6B	115.0 (3)
C8A—C7A—H7AB	121.3	C8B—C7B—H7BA	122.5
C6A—C7A—H7AB	121.3	C6B—C7B—H7BA	122.5
C6A—S1AB—C8A	87.65 (10)	C6B—S1BB—C8B	88.56 (13)
C8A—C7AB—C1A	118.8 (5)	C8B—C7BB—C1B	117.9 (6)
C8A—C7AB—H7AA	120.6	C8B—C7BB—H7BB	121.0
C1A—C7AB—H7AA	120.6	C1B—C7BB—H7BB	121.0
C2A—C1A—C6A	120.37 (17)	C2B—C1B—C6B	120.70 (17)
C2A—C1A—C7AB	139.6 (3)	C2B—C1B—C7BB	140.6 (3)
C6A—C1A—C7AB	100.1 (3)	C6B—C1B—C7BB	98.7 (3)
C2A—C1A—S1A	122.15 (14)	C2B—C1B—S1B	123.93 (14)
C6A—C1A—S1A	117.48 (14)	C6B—C1B—S1B	115.33 (14)
C7AB—C1A—S1A	17.4 (2)	C7BB—C1B—S1B	16.7 (3)
C3A—C2A—C1A	118.86 (17)	C3B—C2B—C1B	118.48 (18)
C3A—C2A—H2AA	120.6	C3B—C2B—H2BA	120.8
C1A—C2A—H2AA	120.6	C1B—C2B—H2BA	120.8
C2A—C3A—C4A	120.93 (18)	C2B—C3B—C4B	121.13 (18)
C2A—C3A—H3AA	119.5	C2B—C3B—H3BA	119.4
C4A—C3A—H3AA	119.5	C4B—C3B—H3BA	119.4
C5A—C4A—C3A	120.82 (18)	C5B—C4B—C3B	120.90 (19)
C5A—C4A—H4AA	119.6	C5B—C4B—H4BA	119.6
C3A—C4A—H4AA	119.6	C3B—C4B—H4BA	119.6
C4A—C5A—C6A	119.29 (17)	C4B—C5B—C6B	119.10 (18)
C4A—C5A—H5AA	120.4	C4B—C5B—H5BA	120.5
C6A—C5A—H5AA	120.4	C6B—C5B—H5BA	120.4
C5A—C6A—C1A	119.72 (17)	C5B—C6B—C1B	119.68 (17)
C5A—C6A—C7A	135.6 (2)	C5B—C6B—C7B	132.9 (2)
C1A—C6A—C7A	104.7 (2)	C1B—C6B—C7B	107.4 (2)
C5A—C6A—S1AB	118.74 (14)	C5B—C6B—S1BB	117.14 (16)
C1A—C6A—S1AB	121.54 (15)	C1B—C6B—S1BB	123.13 (16)
C7A—C6A—S1AB	16.86 (16)	C7B—C6B—S1BB	15.81 (15)
C7AB—C8A—C7A	99.2 (3)	C7BB—C8B—C7B	101.0 (4)
C7AB—C8A—C8A^i	130.4 (3)	C7BB—C8B—C8B^ii	129.9 (4)
C7A—C8A—C8A^i	130.4 (2)	C7B—C8B—C8B^ii	129.1 (2)
C7AB—C8A—S1AB	111.9 (3)	C7BB—C8B—S1BB	111.6 (4)
C7A—C8A—S1AB	12.79 (19)	C7B—C8B—S1BB	10.69 (17)
C8A^i—C8A—S1AB	117.62 (16)	C8B^ii—C8B—S1BB	118.41 (17)
C7AB—C8A—S1A	12.2 (3)	C7BB—C8B—S1B	10.9 (4)
C7A—C8A—S1A	111.4 (2)	C7B—C8B—S1B	111.80 (18)
C8A^i—C8A—S1A	118.19 (16)	C8B^ii—C8B—S1B	119.13 (16)
S1AB—C8A—S1A	124.18 (11)	S1BB—C8B—S1B	122.44 (12)
C8A—C7AB—C1A—C2A	177.7 (2)	C8B—C7BB—C1B—C2B	−176.4 (3)
C8A—C7AB—C1A—C6A	−1.8 (5)	C8B—C7BB—C1B—C6B	2.0 (6)
C8A—C7AB—C1A—S1A	178.0 (12)	C8B—C7BB—C1B—S1B	−174.9 (17)
C8A—S1A—C1A—C2A	178.43 (15)	C8B—S1B—C1B—C2B	−177.67 (16)
C8A—S1A—C1A—C6A	−1.08 (14)	C8B—S1B—C1B—C6B	0.09 (13)
C8A—S1A—C1A—C7AB	−1.3 (8)	C8B—S1B—C1B—C7BB	3.4 (11)
C6A—C1A—C2A—C3A	0.0 (3)	C6B—C1B—C2B—C3B	−0.3 (3)
C7AB—C1A—C2A—C3A	−179.4 (4)	C7BB—C1B—C2B—C3B	177.8 (5)
S1A—C1A—C2A—C3A	−179.48 (14)	S1B—C1B—C2B—C3B	177.30 (13)
C1A—C2A—C3A—C4A	−0.7 (3)	C1B—C2B—C3B—C4B	0.5 (3)
C2A—C3A—C4A—C5A	0.7 (3)	C2B—C3B—C4B—C5B	0.1 (3)
C3A—C4A—C5A—C6A	0.1 (3)	C3B—C4B—C5B—C6B	−0.8 (3)
C4A—C5A—C6A—C1A	−0.8 (3)	C4B—C5B—C6B—C1B	1.0 (3)
C4A—C5A—C6A—C7A	178.2 (2)	C4B—C5B—C6B—C7B	−177.3 (2)
C4A—C5A—C6A—S1AB	178.48 (14)	C4B—C5B—C6B—S1BB	−176.67 (16)
C2A—C1A—C6A—C5A	0.8 (2)	C2B—C1B—C6B—C5B	−0.4 (3)
C7AB—C1A—C6A—C5A	−179.6 (3)	C7BB—C1B—C6B—C5B	−179.2 (3)
S1A—C1A—C6A—C5A	−179.72 (13)	S1B—C1B—C6B—C5B	−178.24 (12)
C2A—C1A—C6A—C7A	−178.54 (19)	C2B—C1B—C6B—C7B	178.28 (18)
C7AB—C1A—C6A—C7A	1.1 (3)	C7BB—C1B—C6B—C7B	−0.5 (4)
S1A—C1A—C6A—C7A	1.0 (2)	S1B—C1B—C6B—C7B	0.4 (2)
C2A—C1A—C6A—S1AB	−178.52 (14)	C2B—C1B—C6B—S1BB	177.11 (16)
C7AB—C1A—C6A—S1AB	1.1 (3)	C7BB—C1B—C6B—S1BB	−1.7 (3)
S1A—C1A—C6A—S1AB	1.0 (2)	S1B—C1B—C6B—S1BB	−0.7 (2)
C8A—C7A—C6A—C5A	−179.4 (2)	C8B—C7B—C6B—C5B	177.48 (18)
C8A—C7A—C6A—C1A	−0.3 (3)	C8B—C7B—C6B—C1B	−1.0 (3)
C8A—C7A—C6A—S1AB	179.8 (8)	C8B—C7B—C6B—S1BB	175.4 (8)
C8A—S1AB—C6A—C5A	−179.53 (14)	C8B—S1BB—C6B—C5B	178.44 (14)
C8A—S1AB—C6A—C1A	−0.24 (16)	C8B—S1BB—C6B—C1B	0.88 (19)
C8A—S1AB—C6A—C7A	−0.2 (6)	C8B—S1BB—C6B—C7B	−3.2 (6)
C1A—C7AB—C8A—C7A	1.6 (4)	C1B—C7BB—C8B—C7B	−2.5 (6)
C1A—C7AB—C8A—C8A^i	−177.8 (3)	C1B—C7BB—C8B—C8B^ii	177.8 (3)
C1A—C7AB—C8A—S1AB	1.8 (5)	C1B—C7BB—C8B—S1BB	−1.7 (7)
C1A—C7AB—C8A—S1A	−177.2 (16)	C1B—C7BB—C8B—S1B	172 (3)
C6A—C7A—C8A—C7AB	−0.7 (3)	C6B—C7B—C8B—C7BB	2.1 (4)
C6A—C7A—C8A—C8A^i	178.7 (2)	C6B—C7B—C8B—C8B^ii	−178.2 (2)
C6A—C7A—C8A—S1AB	−179.7 (10)	C6B—C7B—C8B—S1BB	−173.6 (11)
C6A—C7A—C8A—S1A	−0.4 (3)	C6B—C7B—C8B—S1B	1.1 (3)
C6A—S1AB—C8A—C7AB	−0.9 (3)	C6B—S1BB—C8B—C7BB	0.5 (4)
C6A—S1AB—C8A—C7A	0.2 (8)	C6B—S1BB—C8B—C7B	5.1 (9)
C6A—S1AB—C8A—C8A^i	178.82 (17)	C6B—S1BB—C8B—C8B^ii	−179.00 (18)
C6A—S1AB—C8A—S1A	−0.61 (13)	C6B—S1BB—C8B—S1B	−0.81 (16)
C1A—S1A—C8A—C7AB	2.1 (12)	C1B—S1B—C8B—C7BB	−6 (2)
C1A—S1A—C8A—C7A	0.8 (2)	C1B—S1B—C8B—C7B	−0.65 (18)
C1A—S1A—C8A—C8A^i	−178.41 (17)	C1B—S1B—C8B—C8B^ii	178.71 (17)
C1A—S1A—C8A—S1AB	1.02 (12)	C1B—S1B—C8B—S1BB	0.53 (13)

Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x+1, −y, −z+1.