Tetrakis(3,4-ethylenedioxy-2-thienyl)silane carbon tetrachloride solvate

The structure of tetrakis(3,4-ethyl­ene­dioxy-2-thienyl)­silane carbon tetrachloride solvate, Si(C₆H₅O₂S)₄·CCl₄, has been determined in the noncentrosymmetric space group I. The Si and C atoms of the CCl₄ are located on the fourfold inversion axes. The Si atom has a tetrahedral geometry. The thio­phene ring in the 3,4-ethyl­ene­dioxy­thio­phene group is nearly planar to within 0.005 Å, and the ethyl­ene­dioxy moiety is in a half-chair conformation.

S1. Comment

Thiophene derivatives have attracted attention in the field of materials chemistry due to their ease of derivatization and ability to polymerize by a variety of chemical and electrochemical methods (Roncali, 1997; Jestin et al., 1998; Visy et al., 1996). Polythiophene derivatives show interesting electronic, optical and electrochemical properties. One of the most interesting polythiophene derivatives is poly(3,4-ethylenedioxythiophene) (PEDOT), because it has a much lower bandgap, better environmental stability and higher conductivity than polythiophene (Sotzing et al., 1997). Recently, PEDOT has been utilized in the field of electrochromics because of its highly transmissive oxidized state, opaque deep-blue reduced state and high contrast ratio (Kumar et al., 1998; Sankaran & Reynolds, 1997). In the course of our ongoing research on electrochromic materials, we have synthesized tetrakis(3,4-ethylenedioxy-2-thienyl)silane carbon tetrachloride solvate, (I), as a novel precursor for poly(3,4-ethylenedioxythiophene) and have determined its crystal structure. \sch

The ORTEP drawing of (I) is presented in Fig. 1. Compound (I) cocrystallizes with CCl₄ in a 1:1 ratio in the noncentrosymmetric space group I4. Since Z is 2, the Si atoms reside on the 4 axes at (0,1/2,1/4) and (0,1/2,3/4), as shown in Fig. 2. The asymmetric unit consists of a quarter of an Si atom, one ethylenedioxythienyl ring and a quarter of a CCl₄ molecule. The C atoms of the CCl₄ solvate occupy fourfold inversion axes at the special positions (0,0,0) and (1/2,1/2,1/2), and the Cl atoms are in general positions as shown in Fig. 2.

The coordination sphere around the Si atom is perfectly tetrahedral due to the symmetry definition. The Si atom lies in the thienyl ring plane and each thienyl ring is planar to within an average standard deviation from planarity of the thienyl atoms of 0.005 Å. The Si—C bond length of 1.848 (2) Å is very close to that found in phenylsilane [1.843 (5) Å; Keidel & Bauer, 1956] but shorter than those in tetra(2-thienyl)silane and tetraphenylsilane [1.888 (3) and 1.872 (7) Å, respectively; Glidewell & Sheldrick, 1971]. The average C—S distance [1.727 (6) Å] in the thienyl ring is very similar to the mean C—S distances in 1,2-bis[2-(3,4-ethylenedioxy)thienyl]vinylene and 1,4-bis[2-(3,4-ethylenedioxy)thienyl]benzene [1.725 (3) and 1.728 (2) Å, respectively; Sotzing et al., 1996]. The C—C bond lengths in the thienyl ring are very similar to those of the corresponding C—C bond distances in free thiophene (Bak et al., 1961; Harshbarger & Bauer, 1970). The C3—C4 bond length [1.426 (3) Å] in the thienyl ring is significantly longer than those of C2—C3 [1.364 (3) Å] and C4—C5 [1.354 (3) Å]; however, all three C—C bond lengths differ from normal Csp²—Csp² single [1.48 Å] and Csp²═Csp² double [1.34 Å] bond distances. The average C—S bond distance [1.727 (6) Å] is somewhat shorter than a normal Csp²—S single-bond length [1.759 (8) Å] but is longer than the corresponding C—S distance of free thiophene [1.714 (1) Å; Angelici, 1990]. Therefore, the thienyl ring structure indicates some delocalization of the π-electrons but less than is found in free thiophene. The C2—S—C5 angle [93.4 (1) Å] is the same, to within experimental error, as those in free thiophene, in 3,4-ethylenedioxythiophyene derivatives (Sotzing et al., 1996) and in S-bound thiophene transition metal complexes (Angelici, 1990).

The six-membered dioxane ring is in a half-chair conformation. The structural features of the dioxane moiety in (I) are close to those found in 2-(1,2-dibromoethyl)-1,4-benzodioxan (Barnes & Schroth, 1988) and bis(1,4-benzodioxan)silver(I) perchlorate (Barnes & Blyth, 1985). The angle between the thienyl ring and the C6—C7 bond is 30.4 (2)°. The dihedral angles in the dioxane moiety are as follows: C2—C3—O1—C6 163.8 (2), O1—C6—C7—O2 − 65.4 (3), C4—O2—C7—C6 46.2 (3) and C6—O1—C3—C4 − 17.2 (3)°. The H atoms on the ethylene C atoms have a nearly gauche configuration.

S2. Experimental

To freshly distilled diethyl ether (30 ml) in a Schlenk flask was added 3,4-ethylenedioxythiophene (1.0 g, 7.0 mmol) under an Ar atmosphere. The solution was cooled to 195 K with a dry ice-acetone bath and n-butyllithium (4.4 ml, 1.6 M in n-hexane) was added slowly over 15 min using a dropping funnel. The dry ice-acetone bath was then replaced with an ice bath. After 30 min the ice bath was removed and the resulting light-yellow solution containing a white salt was stirred at room temperature for 2 h. Next, tetrachlorosilane (0.2 ml, 1.7 mmol) was dissolved in distilled diethylether (15 ml) in another Schlenk flask and added slowly via a cannula. After 10 min, the ice bath was removed and the reaction mixture was stirred at room temperature for 4 h. The reaction mixture was then added to CH₂Cl₂ (100 ml) and washed with water (30 ml) and brine (30 ml) twice. The organic phase was dried over MgSO₄, filtered and evaporated to give a light-brown liquid. The crude product was purified by column chromatography (2 × 15 cm, silica gel, CH₂Cl₂ eluent). Evaporation of the eluent under vacuum gave a white solid. This was recrystallized from a saturated CH₂Cl₂ solution by a slow cooling method to give colourless transparent crystals of (I) (0.32 g, 0.54 mmol, 31% yield). Crystals suitable for X-ray crystallography were obtained by very slow cooling using a double Dewar technique in a saturated CCl₄ solution. Spectroscopic analysis, ¹H NMR, δ (acetone-d⁶/DMSO-d⁶): 6.7 (s, 4H), 4.1 (m, 16H); analysis calculated for C₂₄H₂₀O₈S₄Si: C 48.63, H 3.40%; found: C 48.48, H 3.56%.

S3. Refinement

H atoms were located from a difference electronic density map and refined using isotropic displacement parameters.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXTL (Siemens, 1994); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The structure of (I) showing 30% probability displacement ellipsoids and the atomic numbering scheme. The carbon tetrachloride molecule and H atoms are omitted for clarity.
	Fig. 2. The molecular packing diagram of (I).

Tetrakis(3,4-ethylenedioxy-2-thienyl)silane carbon tetrachloride solvate

Crystal data

C24H20O8S4Si·CCl4	Dx = 1.612 Mg m^−3
Mr = 746.54	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4	Cell parameters from 3266 reflections
Hall symbol: I -4	θ = 4–53°
a = 13.1846 (6) Å	µ = 0.74 mm^−1
c = 8.8493 (6) Å	T = 193 K
V = 1538.31 (14) Å^3	Block, colourless
Z = 2	0.41 × 0.18 × 0.18 mm
F(000) = 760

Data collection

Siemens CCD area-detector diffractometer	1557 independent reflections
Radiation source: fine-focus sealed tube	1480 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.000
ϕ and ω scans	θmax = 26.4°, θmin = 2.2°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1997)	h = −16→16
Tmin = 0.751, Tmax = 0.878	k = 0→16
1557 measured reflections	l = 0→11

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.028	Only H-atom displacement parameters refined
wR(F^2) = 0.074	w = 1/[σ^2(Fo^2) + (0.055P)^2 + 0.401P] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max = 0.001
1557 reflections	Δρmax = 0.21 e Å^−3
115 parameters	Δρmin = −0.29 e Å^−3
0 restraints	Absolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.08 (8)

Special details

Experimental. Data were collected over a hemisphere of reciprocal space, by combining three sets of exposures; each set had a different phi angle for the crystal and each exposure of 10 s covered 0.3 in ω. The crystal-to-detector distance was 4.5 cm. A total of 1271 frames were collected. The crystal showed no significant decay. Only reflections with 2θ less than 53° were used for the structure refinement. The structure was solved by direct methods and refined by full matrix least-squares. Anisotropic displacement parameters were used for all non-H atoms.

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
Si	1/2	1	−1/4	0.0196 (2)
S	0.58643 (4)	0.78829 (4)	−0.15379 (6)	0.02697 (15)
Cl	0.89071 (7)	1.00101 (6)	0.88706 (10)	0.0604 (3)
O1	0.36088 (13)	0.92404 (13)	0.03840 (19)	0.0296 (4)
O2	0.40498 (14)	0.72941 (12)	0.1798 (2)	0.0318 (4)
C1	1	1	1	0.0369 (11)
C2	0.49965 (16)	0.88572 (15)	−0.1291 (2)	0.0225 (4)
C3	0.43722 (16)	0.86174 (16)	−0.0114 (3)	0.0217 (4)
C4	0.45871 (17)	0.76650 (17)	0.0579 (3)	0.0246 (5)
C5	0.53702 (18)	0.71714 (18)	−0.0083 (3)	0.0281 (5)
C6	0.29017 (18)	0.8699 (2)	0.1328 (3)	0.0310 (5)
C7	0.3458 (2)	0.80865 (19)	0.2506 (3)	0.0325 (5)
H5	0.569 (2)	0.657 (3)	0.010 (4)	0.044 (9)*
H6A	0.252 (2)	0.827 (2)	0.066 (4)	0.037 (8)*
H6B	0.251 (2)	0.925 (2)	0.181 (3)	0.025 (6)*
H7A	0.300 (2)	0.775 (2)	0.312 (3)	0.033 (7)*
H7B	0.392 (2)	0.843 (2)	0.315 (3)	0.039 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si	0.0203 (3)	0.0203 (3)	0.0182 (6)	0	0	0
S	0.0295 (3)	0.0255 (3)	0.0259 (3)	0.0068 (2)	0.0034 (2)	−0.0005 (2)
Cl	0.0668 (5)	0.0497 (4)	0.0648 (6)	0.0069 (4)	−0.0336 (4)	−0.0064 (4)
O1	0.0294 (9)	0.0293 (8)	0.0303 (9)	0.0059 (7)	0.0084 (7)	0.0037 (7)
O2	0.0384 (9)	0.0282 (8)	0.0288 (9)	−0.0017 (7)	0.0059 (7)	0.0068 (7)
C1	0.0383 (17)	0.0383 (17)	0.034 (3)	0	0	0
C2	0.0246 (11)	0.0196 (10)	0.0234 (12)	0.0027 (8)	−0.0002 (9)	0.0002 (9)
C3	0.0222 (10)	0.0221 (10)	0.0210 (11)	−0.0009 (8)	−0.0007 (8)	−0.0018 (8)
C4	0.0285 (12)	0.0239 (11)	0.0215 (11)	−0.0027 (9)	−0.0025 (9)	−0.0003 (9)
C5	0.0361 (13)	0.0208 (11)	0.0273 (12)	0.0033 (9)	−0.0020 (10)	0.0028 (9)
C6	0.0286 (11)	0.0384 (13)	0.0261 (13)	−0.0028 (10)	0.0032 (11)	−0.0034 (10)
C7	0.0382 (13)	0.0335 (12)	0.0258 (12)	−0.0047 (10)	0.0071 (11)	0.0001 (10)

Geometric parameters (Å, º)

Si—C2	1.848 (2)	O2—C4	1.380 (3)
S—C2	1.734 (2)	O2—C7	1.447 (3)
S—C5	1.721 (3)	Si—C2^i	1.848 (2)
C2—C3	1.364 (3)	Si—C2^ii	1.848 (2)
C3—C4	1.426 (3)	Si—C2^iii	1.848 (2)
C4—C5	1.354 (3)	Cl—C1	1.7537 (8)
C6—C7	1.509 (4)	C1—Cl^iv	1.7537 (8)
O1—C3	1.372 (3)	C1—Cl^v	1.7537 (8)
O1—C6	1.441 (3)	C1—Cl^vi	1.7537 (8)
C2—S—C5	93.42 (11)	C4—O2—C7	111.08 (18)
C3—C2—S	108.83 (16)	C2^i—Si—C2^ii	109.59 (7)
C3—C2—Si	129.22 (17)	C2^i—Si—C2	109.59 (7)
S—C2—Si	121.95 (12)	C2^ii—Si—C2	109.23 (13)
C2—C3—O1	123.3 (2)	C2^i—Si—C2^iii	109.23 (13)
C2—C3—C4	114.4 (2)	C2^ii—Si—C2^iii	109.59 (7)
O1—C3—C4	122.3 (2)	C2—Si—C2^iii	109.59 (7)
C5—C4—O2	124.0 (2)	Cl^iv—C1—Cl	108.95 (3)
C5—C4—C3	112.9 (2)	Cl^iv—C1—Cl^v	108.95 (3)
O2—C4—C3	123.1 (2)	Cl—C1—Cl^v	110.51 (7)
C4—C5—S	110.51 (17)	Cl^iv—C1—Cl^vi	110.51 (7)
O1—C6—C7	110.54 (19)	Cl—C1—Cl^vi	108.95 (3)
O2—C7—C6	110.4 (2)	Cl^v—C1—Cl^vi	108.95 (3)
C3—O1—C6	111.37 (18)
C2—C3—O1—C6	163.8 (2)	Si—C2—C3—O1	−0.7 (3)
O1—C6—C7—O2	−65.4 (3)	S—C2—C3—C4	0.0 (2)
C4—O2—C7—C6	46.2 (3)	Si—C2—C3—C4	−179.82 (17)
C6—O1—C3—C4	−17.2 (3)	C7—O2—C4—C5	164.3 (2)
C5—S—C2—C3	0.57 (18)	C7—O2—C4—C3	−15.5 (3)
C5—S—C2—Si	−179.62 (14)	C2—C3—C4—C5	−0.7 (3)
C2^i—Si—C2—C3	−69.01 (16)	O1—C3—C4—C5	−179.9 (2)
C2^ii—Si—C2—C3	51.07 (18)	C2—C3—C4—O2	179.10 (19)
C2^iii—Si—C2—C3	171.1 (2)	O1—C3—C4—O2	0.0 (3)
C2^i—Si—C2—S	111.22 (19)	O2—C4—C5—S	−178.70 (17)
C2^ii—Si—C2—S	−128.71 (16)	C3—C4—C5—S	1.1 (3)
C2^iii—Si—C2—S	−8.63 (14)	C2—S—C5—C4	−0.99 (19)
S—C2—C3—O1	179.09 (17)	C3—O1—C6—C7	48.1 (3)

Symmetry codes: (i) y−1/2, −x+3/2, −z−1/2; (ii) −x+1, −y+2, z; (iii) −y+3/2, x+1/2, −z−1/2; (iv) −y+2, x, −z+2; (v) −x+2, −y+2, z; (vi) y, −x+2, −z+2.