1-Hydr­oxy-1,1,3,3,3-penta­phenyl­disiloxane, [Si2O(OH)(Ph)5], at 150 K

Tatiana R Amarante; Ana C Coelho; Jacek Klinowski; Isabel S Gonçalves; Filipe A Almeida Paz

doi:10.1107/S1600536807064987

. 2007 Dec 12;64(Pt 1):o239. doi: 10.1107/S1600536807064987

1-Hydroxy-1,1,3,3,3-pentaphenyldisiloxane, [Si₂O(OH)(Ph)₅], at 150 K

Tatiana R Amarante ^a, Ana C Coelho ^a, Jacek Klinowski ^b, Isabel S Gonçalves ^a, Filipe A Almeida Paz ^a,^*

PMCID: PMC2915298 PMID: 21200805

Abstract

In the crystal structure of the title compound, C₃₀H₂₆O₂Si₂, one Si(Ph)₃ residue is bound to another Si(OH)(Ph)₂ residue via a nonlinear Si—O—Si bridge. The asymmetric unit is composed of four [Si₂O(OH)(Ph)₅] molecules. Each pair of adjacent molecules interacts via strong and highly directional O—H⋯O hydrogen bonds connecting neighbouring Si—OH units, and via inter-unit O—H⋯π contacts connecting the second hydroxyl groups with adjacent phenyl groups.

Related literature

For related structures of disiloxane compounds see: Glidewell & Liles (1978 ▶); Hönle et al. (1990 ▶); Morosin & Harrah (1981 ▶); Suwińska et al. (1986 ▶); Wojnowski et al. (2004 ▶). For a crystallographic determination of the title compound at 100 (2) K, see the preceding paper: Coelho et al. (2008 ▶).

Experimental

Crystal data

C₃₀H₂₆O₂Si₂
M _r = 474.69
Triclinic,
a = 15.0113 (12) Å
b = 19.9930 (15) Å
c = 20.1661 (16) Å
α = 65.270 (3)°
β = 71.217 (4)°
γ = 87.173 (4)°
V = 5178.7 (7) Å³
Z = 8
Mo Kα radiation
μ = 0.16 mm⁻¹
T = 150 (2) K
0.30 × 0.22 × 0.12 mm

Data collection

Bruker Kappa APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1998 ▶) T _min = 0.923, T _max = 0.981
96391 measured reflections
17802 independent reflections
8243 reflections with I > 2σ(I)
R _int = 0.120

Refinement

R[F ² > 2σ(F ²)] = 0.079
wR(F ²) = 0.250
S = 1.02
17802 reflections
1229 parameters
H-atom parameters constrained
Δρ_max = 0.56 e Å⁻³
Δρ_min = −0.45 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: APEX2; data reduction: SAINT-Plus (Bruker, 2005 ▶); program(s) used to solve structure: SHELXTL (Bruker, 2001 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536807064987/tk2229sup1.cif

e-64-0o239-sup1.cif^{(63.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807064987/tk2229Isup2.hkl

e-64-0o239-Isup2.hkl^{(869.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O6—H6A⋯O2	0.84	2.03	2.785 (5)	149
O8—H8A⋯O4ⁱ	0.84	1.94	2.735 (5)	158
O2—H2⋯Cg(C67–C72)	0.84	2.66	3.355 (5)	142
O4—H4A⋯Cg(C97–C102)	0.84	2.61	3.249 (5)	134

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Symmetry code: (i) Inline graphic .

Acknowledgments

We are grateful to Fundação para a Ciência e a Tecnologia (FCT, Portugal) for general financial support and also for specific funding towards the purchase of the single-crystal diffractometer.

supplementary crystallographic information

Comment

In a separate crystallographic communication we reported the crystal structure of the title compound, (I), at 100 K in the triclinic P1 space group with two [Si₂O(OH)(Ph)₅] molecular units comprising the asymmetric unit (see Coelho et al., 2008). At 150 K, a decrease in overall long range symmetry, accompanied by an increase in size of the unit cell (by a factor of ca 2) and, consequently, in the number of crystallographically independent binuclear [Si₂O(OH)(Ph)₅] molecular units (from two at 100 K to four at 150 K, see Fig. 1. It is important to stress that the reduction of overall symmetry seems to be essentially due to an increase of thermal motion of the coordinated phenyl groups. Indeed, even though the increase in temperature was only of about 50 K, since the intermolecular interactions between adjacent [Si₂O(OH)(Ph)₅] complexes are of rather weak nature (van der Waals interactions alongside with a number of C—H···π contacts between phenyl groups belonging to adjacent complexes), equivalence between adjacent binuclear units is ultimately destroyed by a combined effect of rotation of the phenyl groups around the Si—C bond with in-plane thermal vibration of the carbon atoms (Figure 1). In fact, the average value of U_eq for the carbon atoms composing the phenyl groups increases from 0.047 Å² (at 100 K) to 0.052 Å² (at 150 K).

The intramolecular geometrical features defining the binuclear [Si₂O(OH)(Ph)₅] units in (I) remain relatively unchanged when compared with those at 100 K (Coelho et al. (2008), Table 1. For the two Si centres within each unit, {SiC₃O} and {SiC₂O₂}, the Si—C and Si—O bond lengths were found in the 1.842 (5)–1.875 (5) and 1.605 (3)–1.648 (3) Å ranges, respectively, in good agreement with those found in related materials and in our determination at 100 K. Each pair of Si centres is interconnected via a µ₂-bridging oxo group, imposing Si···Si internuclear distances ranging from 3.113 (2) Å to 3.216 (2) Å. These distances are shorter than those registered for disiloxanes in which the two Si centres exhibit identical coordination environments (found in the 3.24–3.44 Å range; see Glidewell & Liles, 1978; Hönle et al., 1990; Suwińska et al., 1986). In fact, the presence of distinct coordinating moieties, and the type of intermolecular interactions in which they are involved with neighbouring species, leads to a deformation of the binuclear units through the µ₂-bridge, ultimately imposing shorter Si···Si interatomic distances. The Si—O—Si bond angles for (I) were found in the 145.1 (2)–169.5 (2)° range (Fig. 1 & Table 1) and, as described for the determination of (I) at 100 K, are distributed over two markedly distinct ranges. On the one hand, the high range values are in good agreement with the angle reported by Wojnowski et al. (2004) for [Si₂O(H)(Ph)₅] (ca 163.3°). On the other, the shorter Si—O—Si angles arise due to O—H···π interactions between the O2 and O4 hydroxyl groups and the neighbouring C57→C72 and C97→C101 phenyl groups, respectively (Fig. 1 and Table 2). In fact, besides the strong and highly directional O—H···O hydrogen bond connecting each pair of adjacent [Si₂O(OH)(Ph)₅] molecular units, these weak O—H···π contacts are the second strongest intermolecular interactions in (I). It is clear from Fig. 1 that the thermal motion of the phenyl groups involved in these interactions is significantly more limited than those of the remaining phenyl groups.

As for the structure at 100 K, at 150 K supramolecular entities formed by the combined effected of the O—H···O hydrogen bonds and O—H···π contacts arrange themselves in an ordely fashion in the ac plane of the unit cell forming layers, which close pack along the [010] direction of the unit cell to give the crystal structure of (I), Fig. 2. We also note the presence of a number of C—H···π contacts between phenyl groups (not shown) which help to mediate the crystal packing of individual [Si₂O(H)(Ph)₅] molecular units.

Experimental

Crystals of the title compound were isolated from the same batch as those used for the determination at 100 K of the title compound (see Coelho et al., 2008).