A new pseudopolymorph of perchlorinated neo-penta-silane: the benzene monosolvate Si(SiCl3)4·C6H6.

A new pseudopolymorph of dodeca-chloro-penta-silane, namely a benzene monosolvate, Si5Cl12·C6H6, is described. There are two half mol-ecules of each kind in the asymmetric unit. Both Si5Cl12 mol-ecules are completed by crystallographic twofold symmetry. One of the benzene mol-ecules is located on a twofold rotation axis with two C-H groups located on this rotation axis. The second benzene mol-ecule has all atoms on a general position: it is disordered over two equally occupied orientations. No directional inter-actions beyond normal van der Waals contacts occur in the crystal. © Tillmann et al. 2020.

Chemical context

Since the 1980s, silicon hydrides, such as Si(SiH3)4, have attracted considerable attention as precursors for the liquid phase deposition (LPD) of silicon thin films (Nishimura et al., 1985 ▸). In this context it should be noted that the perchlorinated neo­penta­silane Si(SiCl3)4 (Si5Cl12) is easily accessible in large amounts by the amine-induced disproportionation (Meyer-Wegner et al., 2011 ▸; Tillmann et al., 2012 ▸) of perchloro­polysilanes, e.g. Si2Cl6 or Si3Cl8 (Meyer-Wegner et al., 2011 ▸; Urry, 1970 ▸). Subsequent hydrogenation of Si(SiCl3)4 (I) then yields the neo­penta­silane Si(SiH3)4, which can be used as an LPD agent (Cannady & Zhou, 2008 ▸) (see Fig. 1 ▸).

Figure 1

Amine-induced disproportionation of Si2Cl6 and Si3Cl8: (i) + NMe3, or NMe2Et, or NEt3 in benzene at room temperature; (ii) + LiAlH4 in diethyl ether at room temperature

In this paper we describe the structure of a new pseudo-polymorph of perchlorinated neo­penta­silane (I), namely the benzene monosolvate Si(SiCl3)4·C6H6, and make a comparison of its structure with those of Si(SiCl3)4 (Meyer-Wegner et al., 2011 ▸) and Si(SiCl3)4·SiCl4 (Fleming, 1972 ▸).

Structural commentary

There are two half mol­ecules of each kind in the asymmetric unit of (I). Both Si5Cl12 mol­ecules are completed by crystallographic twofold symmetry, with the rotation axes orientated in the [110] and [10] directions and the central Si atom located on the axis (Fig. 2 ▸). One of the benzene mol­ecules is located on a twofold rotation axis propagating along the a or b axes with two C—H groups located on this rotation axis. The second benzene mol­ecule has all atoms on general positions: it is disordered over two equally occupied orientations about a twofold rotation axis running in the [100] and [010] directions.

Figure 2

A perspective view of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes: (i) −y, −x, −z + ; (ii) 1 − y, 1 − x, −z + ; (iii) −x, y, −z; (iv) 1 − x, y, −z.

Supra­molecular features

A view of the mol­ecular packing of (I) (Fig. 3 ▸) reveals that the benzene mol­ecules fill the voids between the dodeca­chloro­penta­silane mol­ecules. There are no identified directional inter­molecular inter­actions.

Figure 3

Packing diagram of the title compound viewed down [010].

Database survey

There are two already known structures of dodeca­chloro­penta­silane: first, there is pure Si5Cl12 (Meyer-Wegner et al., 2011 ▸; CCDC deposition number 793308) and second, a co-crystal with silicon tetra­chloride (Fleming, 1972 ▸; CCDC deposition number 1592571). In each of these structures, the Si5Cl12 mol­ecule is located on a special position. As noted above, in (I), both mol­ecules in the asymmetric unit are found on a twofold rotation axis. Compound (II) also crystallizes with two mol­ecules in the asymmetric unit. One of them is located on a threefold rotation axis and the other is disordered about a special position of site symmetry . In the second mol­ecule, it is noteworthy that only the Si atoms carrying the Cl atoms are disordered: the central Si atom and the Cl atoms themselves are not disordered. In (III), the Si5Cl12 mol­ecule is located on a special position of site symmetry 23. The central Si atom is located at the inter­section of the twofold and the threefold rotation axes (the twofold rotation axis coincides with a axis). The Si—Si and Si—Cl bond lengths in all three structures agree well (Table 1 ▸).

Table 1

Bond lengths (Å) in the different structures containing Si5Cl12 mol­ecules

For (I), mean values of the two mol­ecules are given. For (II), mean values of the non-disordered mol­ecule are given. Because of the high symmetry of (III), there is only one value for each bond length.

	Si—Si	Si—Cl
(I)	2.324	2.019
(II)	2.340	2.026
(III)	2.332 (9)	1.994 (7)

Synthesis and crystallization

The perchlorinated neo­penta­silane (I) was synthesized according to a literature procedure (Kaczmarczyk & Urry, 1960 ▸). Single crystals of Si(SiCl3)4·C6H6 were grown from a solution of Si(SiCl3)4 in benzene after one week at room temperature.

Si(SiCl (I). 29Si{1H}NMR (C6D6, external TMS): δ = −80.9 [Si(SiCl3)4], δ = 3.5 [Si(SiCl3)4].

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. The H atoms were refined using a riding model with C—H = 0.95 Å and with U iso(H) = 1.2U eq(C). One of the benzene mol­ecules is disordered over two equally occupied orientations: its carbon atoms were isotropically refined. The C—C distances in the non-disordered benzene mol­ecule were restrained to 1.390 (2) Å. The crystal chosen for data collection was found to crystallize as a racemic twin.

Table 2

Experimental details

Crystal data
Chemical formula	Cl12Si5·C6H6
M r	643.96
Crystal system, space group	Tetragonal, P4122
Temperature (K)	173
a, c (Å)	11.9633 (4), 33.7848 (16)
V (Å3)	4835.3 (4)
Z	8
Radiation type	Mo Kα
μ (mm−1)	1.62
Crystal size (mm)	0.28 × 0.18 × 0.16
Data collection
Diffractometer	Stoe IPDS II two-circle
Absorption correction	Multi-scan (X-AREA; Stoe & Cie, 2001 ▸)
T min, T max	0.803, 1.0
No. of measured, independent and observed [I > 2σ(I)] reflections	39180, 5189, 4790
R int	0.047
(sin θ/λ)max (Å−1)	0.642
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.027, 0.075, 1.08
No. of reflections	5189
No. of parameters	207
No. of restraints	5
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.39, −0.42
Absolute structure	Flack x determined using 1905 quotients [(I +)−(I −)]/[(I +)+(I −)] (Parsons et al., 2013 ▸)
Absolute structure parameter	0.48 (5)

Computer programs: X-AREA (Stoe & Cie, 2001 ▸), SHELXS97 (Sheldrick, 2008 ▸), XP in SHELXTL-Plus (Sheldrick, 2008 ▸), SHELXL2018 (Sheldrick, 2015 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989020000900/hb7874sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989020000900/hb7874Isup2.hkl

CCDC reference: 1979631

Additional supporting information: crystallographic information; 3D view; checkCIF report

Cl12Si5·C6H6	Dx = 1.769 Mg m−3
Mr = 643.96	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P4122	Cell parameters from 62511 reflections
a = 11.9633 (4) Å	θ = 1.9–27.6°
c = 33.7848 (16) Å	µ = 1.62 mm−1
V = 4835.3 (4) Å3	T = 173 K
Z = 8	Block, colourless
F(000) = 2528	0.28 × 0.18 × 0.16 mm

Stoe IPDS II two-circle diffractometer	4790 reflections with I > 2σ(I)
ω scans	Rint = 0.047
Absorption correction: multi-scan (X-AREA; Stoe & Cie, 2001)	θmax = 27.1°, θmin = 1.8°
Tmin = 0.803, Tmax = 1.0	h = −14→15
39180 measured reflections	k = −15→15
5189 independent reflections	l = −43→43

Refinement on F2	Hydrogen site location: mixed
Least-squares matrix: full	H-atom parameters constrained
R[F2 > 2σ(F2)] = 0.027	w = 1/[σ2(Fo2) + (0.0375P)2 + 2.8317P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.075	(Δ/σ)max = 0.001
S = 1.08	Δρmax = 0.39 e Å−3
5189 reflections	Δρmin = −0.42 e Å−3
207 parameters	Absolute structure: Flack x determined using 1905 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
5 restraints	Absolute structure parameter: 0.48 (5)
Primary atom site location: structure-invariant direct methods

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

	x	y	z	Uiso*/Ueq	Occ. (<1)
Si1	0.54973 (7)	0.45027 (7)	0.125000	0.0222 (3)
Si2	0.38834 (7)	0.45056 (7)	0.08678 (2)	0.02447 (19)
Si3	0.54972 (8)	0.29277 (8)	0.16530 (3)	0.0264 (2)
Cl21	0.40377 (8)	0.34525 (8)	0.04060 (2)	0.0400 (2)
Cl22	0.25695 (7)	0.39988 (8)	0.11990 (3)	0.0387 (2)
Cl23	0.35776 (8)	0.60671 (7)	0.06658 (3)	0.0384 (2)
Cl31	0.49743 (8)	0.15929 (7)	0.13366 (3)	0.0408 (2)
Cl32	0.70602 (8)	0.26452 (9)	0.18579 (3)	0.0453 (2)
Cl33	0.44514 (8)	0.31660 (9)	0.21128 (3)	0.0412 (2)
Si4	0.04988 (7)	−0.04988 (7)	0.125000	0.0225 (3)
Si5	0.05165 (7)	0.11311 (7)	0.16232 (2)	0.02420 (19)
Si6	0.20502 (8)	−0.05209 (8)	0.08356 (3)	0.0263 (2)
Cl51	−0.05058 (7)	0.09833 (8)	0.20938 (2)	0.0382 (2)
Cl52	−0.00287 (8)	0.24225 (7)	0.12875 (3)	0.0367 (2)
Cl53	0.20867 (7)	0.14553 (8)	0.18124 (3)	0.0379 (2)
Cl61	0.23134 (9)	0.10282 (8)	0.06166 (3)	0.0449 (2)
Cl62	0.17856 (9)	−0.15973 (8)	0.03862 (2)	0.0414 (2)
Cl63	0.34091 (8)	−0.10198 (9)	0.11430 (3)	0.0424 (2)
C1	0.000000	0.3434 (6)	0.000000	0.100 (4)
H1	0.000000	0.263981	0.000000	0.120*
C2	0.0511 (5)	0.4024 (4)	0.03030 (13)	0.094 (2)
H2	0.087169	0.363505	0.051231	0.113*
C3	0.0495 (5)	0.5176 (4)	0.03001 (14)	0.090 (2)
H3	0.083717	0.556596	0.051284	0.107*
C4	0.000000	0.5786 (7)	0.000000	0.087 (3)
H4	0.000000	0.657984	0.000000	0.104*
C5	0.5409 (8)	0.8628 (10)	0.0236 (3)	0.051 (2)*	0.5
H5	0.570943	0.806236	0.040196	0.062*	0.5
C6	0.5561 (8)	0.9738 (11)	0.0335 (3)	0.050 (2)*	0.5
H6	0.594385	0.992910	0.057205	0.059*	0.5
C7	0.5158 (9)	1.0566 (8)	0.0092 (3)	0.054 (3)*	0.5
H7	0.527035	1.132987	0.015732	0.065*	0.5
C5'	0.5145 (10)	0.8339 (8)	0.0086 (3)	0.057 (3)*	0.5
H5'	0.526088	0.757264	0.014687	0.068*	0.5
C6'	0.5559 (9)	0.9177 (12)	0.0335 (3)	0.058 (2)*	0.5
H6'	0.594991	0.897299	0.056942	0.069*	0.5
C7'	0.5410 (10)	1.0290 (11)	0.0247 (4)	0.062 (3)*	0.5
H7'	0.569534	1.085379	0.041783	0.074*	0.5

	U11	U22	U33	U12	U13	U23
Si1	0.0213 (4)	0.0213 (4)	0.0241 (6)	0.0004 (5)	0.0008 (3)	0.0008 (3)
Si2	0.0245 (4)	0.0238 (4)	0.0251 (4)	0.0000 (3)	−0.0010 (3)	0.0009 (3)
Si3	0.0252 (4)	0.0247 (4)	0.0294 (4)	0.0001 (4)	−0.0007 (3)	0.0046 (3)
Cl21	0.0521 (5)	0.0364 (5)	0.0316 (4)	−0.0014 (4)	0.0003 (4)	−0.0084 (3)
Cl22	0.0269 (4)	0.0476 (5)	0.0418 (4)	−0.0054 (4)	0.0051 (3)	0.0042 (4)
Cl23	0.0464 (5)	0.0278 (4)	0.0411 (4)	0.0058 (4)	−0.0079 (4)	0.0060 (3)
Cl31	0.0452 (5)	0.0268 (4)	0.0503 (5)	−0.0048 (4)	−0.0003 (4)	−0.0032 (4)
Cl32	0.0317 (4)	0.0461 (5)	0.0579 (5)	0.0068 (4)	−0.0113 (4)	0.0116 (4)
Cl33	0.0406 (5)	0.0529 (6)	0.0302 (4)	−0.0059 (4)	0.0065 (4)	0.0031 (4)
Si4	0.0214 (4)	0.0214 (4)	0.0245 (6)	0.0000 (5)	0.0006 (3)	0.0006 (3)
Si5	0.0236 (4)	0.0242 (4)	0.0248 (4)	−0.0008 (3)	−0.0010 (3)	−0.0011 (3)
Si6	0.0248 (4)	0.0259 (4)	0.0282 (4)	0.0001 (4)	0.0038 (3)	0.0010 (3)
Cl51	0.0366 (5)	0.0486 (5)	0.0295 (4)	0.0010 (4)	0.0072 (3)	−0.0013 (4)
Cl52	0.0436 (5)	0.0268 (4)	0.0398 (4)	0.0039 (4)	−0.0050 (4)	0.0042 (3)
Cl53	0.0282 (4)	0.0428 (5)	0.0429 (4)	−0.0063 (4)	−0.0069 (3)	−0.0033 (4)
Cl61	0.0489 (5)	0.0325 (4)	0.0533 (5)	−0.0063 (4)	0.0126 (4)	0.0108 (4)
Cl62	0.0520 (5)	0.0404 (5)	0.0317 (4)	0.0053 (4)	0.0022 (4)	−0.0084 (4)
Cl63	0.0274 (4)	0.0505 (5)	0.0494 (5)	0.0067 (4)	−0.0039 (4)	0.0003 (4)
C1	0.074 (6)	0.043 (4)	0.184 (11)	0.000	0.056 (7)	0.000
C2	0.068 (4)	0.147 (7)	0.067 (4)	0.011 (4)	0.001 (3)	0.055 (4)
C3	0.070 (4)	0.138 (6)	0.060 (3)	−0.026 (4)	0.006 (3)	−0.037 (4)
C4	0.067 (5)	0.068 (5)	0.125 (8)	0.000	0.040 (5)	0.000

Si1—Si2	2.3227 (11)	Si6—Cl61	2.0202 (13)
Si1—Si2i	2.3228 (11)	C1—C2	1.3855 (18)
Si1—Si3i	2.3246 (11)	C1—C2iii	1.3855 (18)
Si1—Si3	2.3247 (11)	C1—H1	0.9500
Si2—Cl21	2.0138 (12)	C2—C3	1.378 (3)
Si2—Cl23	2.0221 (12)	C2—H2	0.9500
Si2—Cl22	2.0225 (12)	C3—C4	1.3824 (18)
Si3—Cl33	2.0150 (13)	C3—H3	0.9500
Si3—Cl31	2.0209 (13)	C4—H4	0.9500
Si3—Cl32	2.0223 (13)	C5—C6	1.382 (15)
Si4—Si5	2.3221 (11)	C5—H5	0.9500
Si4—Si5ii	2.3222 (11)	C6—C7	1.375 (14)
Si4—Si6	2.3250 (11)	C6—H6	0.9500
Si4—Si6ii	2.3251 (11)	C7—H7	0.9500
Si5—Cl51	2.0138 (12)	C5'—C6'	1.399 (15)
Si5—Cl53	2.0218 (12)	C5'—H5'	0.9501
Si5—Cl52	2.0243 (12)	C6'—C7'	1.376 (15)
Si6—Cl62	2.0158 (13)	C6'—H6'	0.9500
Si6—Cl63	2.0194 (13)	C7'—H7'	0.9500
Si2—Si1—Si2i	107.85 (6)	C2—C1—C2iii	118.8 (7)
Si2—Si1—Si3i	110.38 (3)	C2—C1—H1	120.6
Si2i—Si1—Si3i	109.07 (3)	C2iii—C1—H1	120.6
Si2—Si1—Si3	109.07 (3)	C3—C2—C1	119.9 (6)
Si2i—Si1—Si3	110.37 (3)	C3—C2—H2	120.1
Si3i—Si1—Si3	110.06 (7)	C1—C2—H2	120.1
Cl21—Si2—Cl23	109.46 (5)	C2—C3—C4	122.6 (6)
Cl21—Si2—Cl22	108.20 (6)	C2—C3—H3	118.7
Cl23—Si2—Cl22	108.85 (6)	C4—C3—H3	118.7
Cl21—Si2—Si1	110.71 (5)	C3iii—C4—C3	116.3 (7)
Cl23—Si2—Si1	109.84 (5)	C3iii—C4—H4	121.9
Cl22—Si2—Si1	109.75 (4)	C3—C4—H4	121.9
Cl33—Si3—Cl31	109.11 (6)	C6—C5—C5iv	106.0 (6)
Cl33—Si3—Cl32	109.50 (6)	C6—C5—H5	119.4
Cl31—Si3—Cl32	109.58 (6)	C5iv—C5—H5	134.6
Cl33—Si3—Si1	109.69 (5)	C5—C6—C7	120.0 (9)
Cl31—Si3—Si1	109.31 (5)	C5—C6—C7iv	104.5 (8)
Cl32—Si3—Si1	109.63 (5)	C5—C6—H6	120.0
Si5—Si4—Si5ii	108.07 (6)	C7—C6—H6	120.0
Si5—Si4—Si6	109.22 (3)	C7iv—C6—H6	135.5
Si5ii—Si4—Si6	110.07 (3)	C7iv—C7—C6	133.9 (6)
Si5—Si4—Si6ii	110.08 (3)	C6—C7—C6iv	103.4 (9)
Si5ii—Si4—Si6ii	109.22 (3)	C7iv—C7—H7	105.9
Si6—Si4—Si6ii	110.15 (7)	C6—C7—H7	120.2
Cl51—Si5—Cl53	109.35 (5)	C6iv—C7—H7	136.4
Cl51—Si5—Cl52	108.28 (6)	C5'iv—C5'—C6'	134.3 (6)
Cl53—Si5—Cl52	109.28 (6)	C5'iv—C5'—H5'	105.1
Cl51—Si5—Si4	110.45 (5)	C6'—C5'—H5'	120.6
Cl53—Si5—Si4	109.95 (5)	C6'iv—C5'—H5'	136.3
Cl52—Si5—Si4	109.50 (5)	C7'—C6'—C5'	121.1 (10)
Cl62—Si6—Cl63	108.97 (6)	C7'—C6'—H6'	119.4
Cl62—Si6—Cl61	109.56 (6)	C5'—C6'—H6'	119.4
Cl63—Si6—Cl61	109.51 (6)	C5'iv—C6'—H6'	134.0
Cl62—Si6—Si4	109.60 (5)	C6'—C7'—C7'iv	104.6 (7)
Cl63—Si6—Si4	109.65 (5)	C6'—C7'—H7'	120.6
Cl61—Si6—Si4	109.54 (5)	C7'iv—C7'—H7'	134.8
C2iii—C1—C2—C3	0.6 (4)	C7iv—C6—C7—C6iv	−1 (2)
C1—C2—C3—C4	−1.2 (9)	C5'iv—C5'—C6'—C7'	0 (4)
C2—C3—C4—C3iii	0.6 (4)	C6'iv—C5'—C6'—C7'	0.0 (10)
C5iv—C5—C6—C7	−1.7 (13)	C6'iv—C5'—C6'—C5'iv	0 (3)
C5iv—C5—C6—C7iv	−1.2 (10)	C5'—C6'—C7'—C7'iv	−0.1 (14)
C5—C6—C7—C7iv	2 (3)	C5'iv—C6'—C7'—C7'iv	−0.2 (11)
C5—C6—C7—C6iv	1.0 (9)