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ISSN: 2056-9890

(E)-1,2-Bis{4-[dimeth­yl(vin­yl)silyl]­phenyl}­ethene

aDepartment of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
*Correspondence e-mail: mkubicki@amu.edu.pl

(Received 21 November 2007; accepted 24 November 2007; online 6 December 2007)

The mol­ecule of the title compound, C32H34Si2, is situated about a centre of symmetry. The whole diphenyl­ethene fragment is planar and the Car—Si—C3 group is rotated by ca 30° with respect to the plane of the benzene ring. The crystal structure is stabilized by some C—H⋯π contacts as well as van der Waals inter­actions.

Related literature

For related literature, see: JanBen & Krause (2005[JanBen, Ch. E. & Krause, N. (2005). Eur. J. Org. Chem. pp. 2322-2329.]); Maciejewski et al. (2003[Maciejewski, H., Pawluć, P., Marciniec, B., Kownacki, I., Maciejewska, W. & Majchrzak, M. (2003). Polycarbosilanes as Precursors of Novel Membrane Materials, in Organosilicon Chemistry V From Molecules to Materials, edited by N. Auner & J. Weis, Ch. 3, pp. 641-644. Weinheim: Verlag Chemie.]); Majchrzak et al. (2005[Majchrzak, M., Marciniec, B. & Itami, Y. (2005). Adv. Synth. Catal. 347, 1285-1294.], 2007[Majchrzak, M., Ludwiczak, M., Bayda, M., Marciniak, B. & Marciniec, B. (2007). J. Polym. Sci. Part A Polym. Chem. 46, 127-137.]).

[Scheme 1]

Experimental

Crystal data
  • C22H28Si2

  • Mr = 348.62

  • Monoclinic, C 2/c

  • a = 21.762 (2) Å

  • b = 6.2880 (9) Å

  • c = 19.159 (2) Å

  • β = 124.05 (2)°

  • V = 2172.2 (7) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.16 mm−1

  • T = 295 (2) K

  • 0.3 × 0.2 × 0.15 mm

Data collection
  • Kuma KM4CCD four-circle diffractometer

  • Absorption correction: none

  • 5962 measured reflections

  • 2116 independent reflections

  • 1441 reflections with I > 2σ(I)

  • Rint = 0.028

Refinement
  • R[F2 > 2σ(F2)] = 0.045

  • wR(F2) = 0.120

  • S = 0.99

  • 2116 reflections

  • 165 parameters

  • All H-atom parameters refined

  • Δρmax = 0.25 e Å−3

  • Δρmin = −0.22 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C12—H12ACg1i 0.88 (3) 2.99 (3) 3.872 (3) 174 (2)
C13—H13CCg1ii 0.97 (3) 3.03 (3) 3.912 (4) 152 (2)
Symmetry codes: (i) [-x+1, y, -z+{\script{1\over 2}}]; (ii) -x+1, -y+1, -z+1. Cg1 is the centroid of the C1–C6 ring.

Data collection: CrysAlis CCD (Oxford Diffraction, 2006[Oxford Diffraction (2006). CrysAlis CCD (Version 1.171.29.9) and CrysAlis RED (Version 1.171.29.9). Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]); cell refinement: CrysAlis RED (Oxford Diffraction, 2006[Oxford Diffraction (2006). CrysAlis CCD (Version 1.171.29.9) and CrysAlis RED (Version 1.171.29.9). Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: XP (Siemens, 1989[Siemens (1989). XP. Stereochemical Workstation Operation Manual. Release 3.4. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. ]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

The synthesis of {(E)-1,2-bis(4-(dimethyl(vinyl)silyl)phenyl)}ethene, (I), consisted of two steps. During first step, the well know metathesis reaction of 4-bromostyrene was applied to obtain {(E)-1,2-bis(4-bromophenyl)}ethene which was used as a substrate for the second step, the typical reaction between an aryl-halide derivative of an olefin, a Grignard reagent generated in situ and vinylchlorosilane. This kind of vinylsilane-stilbene can be used as a very efficient monomer for the synthesis of arylene-silylene-vinylene polymers, polycarbosilanes or co-polymers with suitable aromatic olefin via silylative coupling polycondensation (SCP) or polyhydrosilylation reactions (Majchrzak et al., 2005, 2007; Maciejewski et al., 2003).

The molecule of (I) is centrosymmetric with the mid-point of the central C41?C41A bond lying on a centre of symmetry (Fig. 1). The phenyl rings (planar within 0.0046 (14) Å) are, from symmetry, co-planar. As the C41 and Si1 atoms are almost co-planar with these rings (deviation from the least-squares plane = 0.009 (3)Å and 0.054 (3) Å, respectively), the whole diphenylethene fragment is planar. The C(ar)—Si—C3 group is rotated by ca 30° with respect to to the plane of the phenyl ring, as can be seen from the values of C2—C1—Si—C(X) torsion angles: 28.5 (2)° for X = 13, -92.5 (2)° for X = 12, and 148.0 (2)° for X = 11. The crystal structure is stabilized by some relatively directional C—H···π contacts as well as van der Waals interactions.

Related literature top

For related literature, see: JanBen & Krause (2005); Maciejewski et al. (2003); Majchrzak et al. (2005, 2007).

Experimental top

First Step: A solution of 4-bromostyrene (6.095 g, 33.30 mmol) in THF (35 ml) was placed in a 50 ml glass two-neck mini reactor which was fitted with a condenser connected with an inert gas line. The Hoveyda–Grubbs catalyst 1st generation (10 mg, 0.017 mmol) was added and the reaction mixture was heated at 316–318 K and left for 5 h. The crude product was precipitated partially from solution. After the reaction was completed, the mixture was cooled to room temperature and the excess of organic solvent was evaporated under high vacuum. The mix of yellowish crystals was recovered by filtration and washed with cold hexane (3 x 10 ml). The residue was recrystallized from ethanol to provide 5.46 g (16.15 mmol, yield 97%) (E)-4,4'-dibromostilbene as a colorless solid. 1H NMR (CDCl3, δ (p.p.m.)): 7.06 (s, 2H, –CH=CH-), 7.42 (d, JHH = 8.80 Hz, 4H, o-C6H4-Br), 7.52 (d, JHH = 8.75 Hz, 4H, m-C6H4-Br). 13C NMR (CDCl3, δ (p.p.m.)): 122.6 (Br—Ci<), 127.3 (-CH=CH–), 129.8 (Br-m-C6H4–), 132.6 (Br-o-C6H4–), 137.1 (>Ci-CH=). MS—EI (M/z (%)) 338 (100) [M+], 258 (17), 178 (85), 152 (8), 89 (6). HRMS (m/z) calcd. for C14H10Br2: 335.91493, found: 335.91374. m. p. 481–489 K, Lit. (JanBen & Krause, 2005): 483 K.

Second Step: A solution of (E)-4,4'-dibromostilbene (3 g, 8.87 mmol) in THF (15 ml) was added dropwise to a suspension of Mg (0.518 g, 21.30 mmol, whose surface was activated by use of 1,2-dibromomethane (50 µL) and vinyldimethylchlorosilane (2.35 g, 19.51 mmol) in slighly warm THF (15 ml). After the addition was completed, the reaction mixture was heated at 318 K for 4 h. The mixture was cooled to room temperature, water (2 ml) was added, and the whole was filtered. The organic phase was left overnight with magnesium sulfate. The solvent was then evaporated and the residual solid was washed by cold hexane (2 x 15 ml). The isolated compound was recrystallized from ethanol to yield 2.1 g of (I) (6.02 mmol, yield 68%) as a colourless solid. 1H NMR (CDCl3, δ(p.p.m.)): 0.29 (s, 12H, –CH3), 5.82 (dd, 2H, JHH = 3.8, 20.1 Hz, –CH=CH2), 6.11 (dd, 2H, JHH = 3.8, 15.1 Hz, –CH=CH2), 6.34 (dd, 2H, JHH = 14.6, 20.1 Hz, –CH=CH2), 7.11 (s, 2H, –CH=CH-), 7.48 (d, 4H, o-C6H4-Si), 7.54 (d, 4H, m-C6H4-Si). 13C NMR (CDCl3, δ(p.p.m.)): -2.8, 127.3, 129.8, 135.9, 136.3, 137.8, 139.3, 140.1. 29Si NMR (CDCl3, δ(p.p.m.)): -10.60. HRMS (m/z) calcd. for C22H28Si2: 348.17295, found 348.17284. Analysis: found C 75.72, H 8.09%. C22H28Si2 requires: C 75.79, H 8.1%.

Refinement top

Hydrogen atoms were found in difference Fourier maps and freely refined so that the range of C= H = 0.88 (3) to 1.09 (4) Å.

Structure description top

The synthesis of {(E)-1,2-bis(4-(dimethyl(vinyl)silyl)phenyl)}ethene, (I), consisted of two steps. During first step, the well know metathesis reaction of 4-bromostyrene was applied to obtain {(E)-1,2-bis(4-bromophenyl)}ethene which was used as a substrate for the second step, the typical reaction between an aryl-halide derivative of an olefin, a Grignard reagent generated in situ and vinylchlorosilane. This kind of vinylsilane-stilbene can be used as a very efficient monomer for the synthesis of arylene-silylene-vinylene polymers, polycarbosilanes or co-polymers with suitable aromatic olefin via silylative coupling polycondensation (SCP) or polyhydrosilylation reactions (Majchrzak et al., 2005, 2007; Maciejewski et al., 2003).

The molecule of (I) is centrosymmetric with the mid-point of the central C41?C41A bond lying on a centre of symmetry (Fig. 1). The phenyl rings (planar within 0.0046 (14) Å) are, from symmetry, co-planar. As the C41 and Si1 atoms are almost co-planar with these rings (deviation from the least-squares plane = 0.009 (3)Å and 0.054 (3) Å, respectively), the whole diphenylethene fragment is planar. The C(ar)—Si—C3 group is rotated by ca 30° with respect to to the plane of the phenyl ring, as can be seen from the values of C2—C1—Si—C(X) torsion angles: 28.5 (2)° for X = 13, -92.5 (2)° for X = 12, and 148.0 (2)° for X = 11. The crystal structure is stabilized by some relatively directional C—H···π contacts as well as van der Waals interactions.

For related literature, see: JanBen & Krause (2005); Maciejewski et al. (2003); Majchrzak et al. (2005, 2007).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1989); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1] Fig. 1. Molecular structure of (I) showing displacement ellipsoids at the 50% probability level and the atom numbering scheme. The hydrogen atoms are drawn as spheres with arbitrary radii. The unlabelled half of the molecule is related by the symmetry operation: 1/2 - x, 5/2 - y, -z.
(E)-1,2-Bis{4-[dimethyl(vinyl)silyl]phenyl}ethene top
Crystal data top
C22H28Si2F(000) = 752
Mr = 348.62Dx = 1.066 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 2322 reflections
a = 21.762 (2) Åθ = 5–22°
b = 6.2880 (9) ŵ = 0.16 mm1
c = 19.159 (2) ÅT = 295 K
β = 124.05 (2)°Prism, colourless
V = 2172.2 (7) Å30.3 × 0.2 × 0.15 mm
Z = 4
Data collection top
Kuma KM4CCD four-circle
diffractometer
1441 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.028
Graphite monochromatorθmax = 26.0°, θmin = 3.4°
ω scansh = 2625
5962 measured reflectionsk = 75
2116 independent reflectionsl = 1923
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.120All H-atom parameters refined
S = 0.99 w = 1/[σ2(Fo2) + (0.07P)2]
where P = (Fo2 + 2Fc2)/3
2116 reflections(Δ/σ)max = 0.011
165 parametersΔρmax = 0.25 e Å3
0 restraintsΔρmin = 0.22 e Å3
Crystal data top
C22H28Si2V = 2172.2 (7) Å3
Mr = 348.62Z = 4
Monoclinic, C2/cMo Kα radiation
a = 21.762 (2) ŵ = 0.16 mm1
b = 6.2880 (9) ÅT = 295 K
c = 19.159 (2) Å0.3 × 0.2 × 0.15 mm
β = 124.05 (2)°
Data collection top
Kuma KM4CCD four-circle
diffractometer
1441 reflections with I > 2σ(I)
5962 measured reflectionsRint = 0.028
2116 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0450 restraints
wR(F2) = 0.120All H-atom parameters refined
S = 0.99Δρmax = 0.25 e Å3
2116 reflectionsΔρmin = 0.22 e Å3
165 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*/Ueq
C10.51385 (10)0.4316 (3)0.38537 (10)0.0464 (4)
Si10.41638 (3)0.33021 (8)0.33072 (3)0.0486 (2)
C110.35377 (13)0.5625 (4)0.30334 (19)0.0733 (7)
H110.3499 (16)0.626 (4)0.3411 (18)0.118 (12)*
C1110.30599 (16)0.6356 (5)0.2302 (2)0.1040 (10)
H11A0.2932 (18)0.546 (5)0.175 (2)0.163 (14)*
H11B0.2738 (19)0.779 (6)0.221 (2)0.161 (12)*
C120.3915 (2)0.1875 (5)0.23335 (17)0.0760 (7)
H12A0.3940 (15)0.270 (4)0.1977 (17)0.108 (9)*
H12B0.3425 (16)0.138 (4)0.2051 (17)0.114 (10)*
H12C0.4199 (16)0.075 (4)0.2443 (18)0.123 (12)*
C130.41000 (17)0.1498 (5)0.40318 (18)0.0709 (7)
H13A0.4377 (16)0.032 (5)0.4133 (17)0.118 (11)*
H13B0.3635 (16)0.098 (4)0.3774 (16)0.105 (9)*
H13C0.4297 (14)0.219 (4)0.4570 (18)0.110 (9)*
C20.57489 (11)0.3167 (3)0.44767 (13)0.0557 (5)
H20.5684 (11)0.186 (3)0.4625 (13)0.074 (6)*
C30.64669 (11)0.3892 (3)0.48563 (13)0.0573 (5)
H30.6870 (11)0.309 (3)0.5288 (13)0.070 (6)*
C40.66139 (9)0.5860 (3)0.46398 (10)0.0479 (4)
C410.73897 (11)0.6599 (3)0.50658 (12)0.0523 (5)
H410.7708 (11)0.565 (3)0.5483 (12)0.070 (6)*
C50.60055 (11)0.7024 (3)0.40152 (12)0.0561 (5)
H50.6066 (10)0.837 (3)0.3870 (11)0.053 (5)*
C60.52923 (11)0.6282 (3)0.36415 (12)0.0540 (5)
H60.4892 (11)0.720 (3)0.3224 (13)0.068 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0505 (10)0.0467 (10)0.0418 (9)0.0040 (8)0.0258 (8)0.0000 (8)
Si10.0483 (3)0.0469 (3)0.0455 (3)0.0072 (2)0.0232 (3)0.0017 (2)
C110.0626 (14)0.0618 (14)0.0896 (18)0.0025 (11)0.0389 (14)0.0000 (13)
C1110.0713 (18)0.094 (2)0.123 (3)0.0154 (16)0.0397 (19)0.026 (2)
C120.093 (2)0.0719 (17)0.0589 (15)0.0191 (16)0.0399 (15)0.0137 (13)
C130.0662 (16)0.0803 (18)0.0668 (16)0.0121 (14)0.0376 (14)0.0092 (14)
C20.0566 (12)0.0506 (11)0.0546 (12)0.0064 (9)0.0279 (10)0.0076 (9)
C30.0523 (12)0.0584 (12)0.0508 (11)0.0010 (9)0.0226 (10)0.0137 (9)
C40.0479 (10)0.0543 (10)0.0404 (10)0.0045 (8)0.0241 (8)0.0013 (8)
C410.0504 (11)0.0580 (12)0.0427 (10)0.0026 (10)0.0225 (9)0.0048 (10)
C50.0565 (12)0.0522 (12)0.0550 (12)0.0068 (9)0.0285 (10)0.0119 (9)
C60.0490 (11)0.0536 (11)0.0508 (11)0.0005 (9)0.0227 (9)0.0110 (9)
Geometric parameters (Å, º) top
C1—C21.391 (3)C13—H13B0.90 (3)
C1—C61.399 (2)C13—H13C0.97 (3)
C1—Si11.8748 (18)C2—C31.380 (3)
Si1—C121.857 (2)C2—H20.91 (2)
Si1—C131.857 (2)C3—C41.398 (2)
Si1—C111.862 (2)C3—H30.95 (2)
C11—C1111.275 (4)C4—C51.395 (3)
C11—H110.87 (3)C4—C411.480 (2)
C111—H11A1.08 (3)C41—C41i1.309 (3)
C111—H11B1.09 (4)C41—H410.923 (19)
C12—H12A0.88 (3)C5—C61.377 (3)
C12—H12B0.94 (3)C5—H50.924 (17)
C12—H12C0.88 (3)C6—H60.97 (2)
C13—H13A0.90 (3)
C2—C1—C6116.06 (17)H13A—C13—H13B103 (2)
C2—C1—Si1122.72 (13)Si1—C13—H13C110.2 (16)
C6—C1—Si1121.21 (14)H13A—C13—H13C107 (2)
C12—Si1—C13110.72 (15)H13B—C13—H13C116 (2)
C12—Si1—C11109.90 (15)C3—C2—C1122.40 (18)
C13—Si1—C11109.92 (14)C3—C2—H2117.6 (14)
C12—Si1—C1109.15 (12)C1—C2—H2120.0 (14)
C13—Si1—C1108.97 (11)C2—C3—C4121.02 (19)
C11—Si1—C1108.13 (9)C2—C3—H3120.5 (12)
C111—C11—Si1127.6 (3)C4—C3—H3118.4 (12)
C111—C11—H11110.4 (19)C5—C4—C3117.00 (17)
Si1—C11—H11121.5 (19)C5—C4—C41123.39 (16)
C11—C111—H11A119.2 (17)C3—C4—C41119.61 (17)
C11—C111—H11B122.3 (17)C41i—C41—C4126.4 (2)
H11A—C111—H11B118 (2)C41i—C41—H41123.1 (13)
Si1—C12—H12A112.7 (18)C4—C41—H41110.3 (12)
Si1—C12—H12B109.7 (17)C6—C5—C4121.37 (18)
H12A—C12—H12B107 (2)C6—C5—H5117.6 (11)
Si1—C12—H12C112.1 (19)C4—C5—H5120.9 (11)
H12A—C12—H12C108 (3)C5—C6—C1122.13 (19)
H12B—C12—H12C107 (2)C5—C6—H6117.1 (12)
Si1—C13—H13A109.9 (18)C1—C6—H6120.8 (12)
Si1—C13—H13B109.9 (16)
Symmetry code: (i) x+3/2, y+3/2, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C12—H12A···Cg1ii0.88 (3)2.99 (3)3.872 (3)174 (2)
C13—H13C···Cg1iii0.97 (3)3.03 (3)3.912 (4)152 (2)
Symmetry codes: (ii) x+1, y, z+1/2; (iii) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC22H28Si2
Mr348.62
Crystal system, space groupMonoclinic, C2/c
Temperature (K)295
a, b, c (Å)21.762 (2), 6.2880 (9), 19.159 (2)
β (°) 124.05 (2)
V3)2172.2 (7)
Z4
Radiation typeMo Kα
µ (mm1)0.16
Crystal size (mm)0.3 × 0.2 × 0.15
Data collection
DiffractometerKuma KM4CCD four-circle
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
5962, 2116, 1441
Rint0.028
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.045, 0.120, 0.99
No. of reflections2116
No. of parameters165
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.25, 0.22

Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1989).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C12—H12A···Cg1i0.88 (3)2.99 (3)3.872 (3)174 (2)
C13—H13C···Cg1ii0.97 (3)3.03 (3)3.912 (4)152 (2)
Symmetry codes: (i) x+1, y, z+1/2; (ii) x+1, y+1, z+1.
 

References

First citationJanBen, Ch. E. & Krause, N. (2005). Eur. J. Org. Chem. pp. 2322–2329.  Google Scholar
First citationMaciejewski, H., Pawluć, P., Marciniec, B., Kownacki, I., Maciejewska, W. & Majchrzak, M. (2003). Polycarbosilanes as Precursors of Novel Membrane Materials, in Organosilicon Chemistry V From Molecules to Materials, edited by N. Auner & J. Weis, Ch. 3, pp. 641–644. Weinheim: Verlag Chemie.  Google Scholar
First citationMajchrzak, M., Marciniec, B. & Itami, Y. (2005). Adv. Synth. Catal. 347, 1285–1294.  Web of Science CrossRef CAS Google Scholar
First citationMajchrzak, M., Ludwiczak, M., Bayda, M., Marciniak, B. & Marciniec, B. (2007). J. Polym. Sci. Part A Polym. Chem. 46, 127–137.  Web of Science CrossRef Google Scholar
First citationOxford Diffraction (2006). CrysAlis CCD (Version 1.171.29.9) and CrysAlis RED (Version 1.171.29.9). Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.  Google Scholar
First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
First citationSiemens (1989). XP. Stereochemical Workstation Operation Manual. Release 3.4. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.  Google Scholar

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