An electron diffraction determination of the molecular structures of perchlorodisiloxane and methoxytrifluorosilane

Airey, W.; Glidewell, C.; Robiette, A. G.; Sheldrick, George M.

doi:10.1016/0022-2860(71)80019-4

Cited by 69 publications

(21 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…References: (a) Almenningen et al (1963);(b) Csakvari, Wagner, G6m6ry & Mijlhoff (1976); (c) Airey et al (1970): (d) Airey, Glidewell, Robiette & Sheldrick (1971); (e) Glidewell & Liles (1978). * Crystallographic C t symmetry.…”

Section: (B) Molecular Conformationsmentioning

confidence: 99%

The crystal and molecular structures of disiloxane (at 108 K) and hexamethyldisiloxane (at 148 K)

Barrow¹,

Ebsworth²,

Harding³

1979

Acta Crystallogr Sect B

125

View full text Add to dashboard Cite

THE STRUCTURES OF DISILOXANE AND HEXAMETHYLDISILOXANE equipment and microdensitometer intensities were obtained from films exposed using Cu Ka radiation. The structures were refined to R = 4-2% over 403 reflexions for disiloxane, and R = 3.5% over 1256 reflexions for hexamethyldisiloxane. Crystalline disiloxane has distorted mm2 molecular symmetry with Si-O = 1.631 (6) A and Si-O-Si = 142.2 (3) °. Crystalline hexamethyldisiloxane has distorted m molecular symmetry with Si-O = 1.626 (5) A and Si-O-Si = 148.8 (2) °. Molecules of disiloxane form infinite chains as a result of weak, but highly directional, intermolecular Si..-O interactions (3.115 A). Hexamethyldisiloxane exists as discrete molecules with no short intermolecular contacts. IntroductionIn water, dimethyl ether, F20 and C120 , the angle at oxygen is close to or less than the tetrahedral value. In silicates and disiloxanes, the angle at oxygen is very much wider. Moreover, it increases from the apparent value of 144.1 ° in disiloxane itself (as measured by electron diffraction in the gas phase) to 180 ° in crystalline hexaphenyldisiloxane. Values for Si-O-Si and Si-O distances in a number of disiloxanes and related compounds are given in Table 7.Most of the features in the vibrational spectra of disiloxane can be interpreted in terms of a model with a linear heavy-atom skeleton (Lord, Robinson & Schumb, 1956). This apparently conflicts with the structure as determined by electron diffraction (Almenningen, Bastiansen, Ewing, Hedberg & Traetteberg, 1963); the two can be reconciled if the molecule is regarded as 'quasi-linear': bent but with a skeletal bending vibration that is low in frequency and large in amplitude. Under these conditions the language of the conventional point-group analysis becomes inappropriate; permutation group theory must be used instead. The appropriate permutation group is isomorphous with D3h , leading to selection rules that are effectively the same as for a molecule with a linear heavy-atom skeleton. A detailed analysis of the weak Raman feature corresponding to the overtone of the skeletal bending mode has led Durig, Flanagan & Kalasinsky (1977) to propose a potential surface with a hump at a linear configuration of height 112 cm -1, and a minimum corresponding to a Si-O-Si angle of 149 °.The concept of quasi-linearity is by now well established, but little is known about the structures of quasilinear molecules in the solid state. The vibrational spectra of disiloxane and hexachlorodisiloxane change on crystallization, implying that there might be associated changes in structure. Disiloxane is a clearly recognized example of quasi-linearity, while it is suggested that features in the Raman spectra of hexamethyldisiloxane imply that this molecule too should be regarded as quasi-linear. We here present the crystal structures of disiloxane and of hexamethyldisiloxane. ExperimentalCrystallographic data ProcedurePure samples of disiloxane and hexamethyldisiloxane were sealed into glass capillaries, which were mounted on Tufnol ins...

show abstract

Section: (B) Molecular Conformationsmentioning

confidence: 99%

The crystal and molecular structures of disiloxane (at 108 K) and hexamethyldisiloxane (at 148 K)

Barrow¹,

Ebsworth²,

Harding³

1979

Acta Crystallogr Sect B

125

View full text Add to dashboard Cite

show abstract

“…Organodisiloxanes appear to adopt either a bent configuration with an SiOSi angle of 140-160 ° or a linear configuration with SiOSi equal to 180 °. The value of the SiOSi angle has been determined by gas-phase electron diffraction for O(SiHa) 2 (Almenningen, Bastiansen, Ewing, Hedberg & Tra~tteberg, 1963), for O(SiF3) 2 (Airey, Glidewell, Rankin, Robiette, Sheldrick & Cruickshank, 1970) and for O(SiCH3) 2 (Airey, Glidewell, Robiette & Sheldrick, 1971) to be 144.1, 155.7 and 146 °, respectively. From lowtemperature X-ray diffraction analyses of single 0108-2701/86/010064-04501.50 crystals, the SiOSi angle has been found to have a value of 142.2 ° for O(SiH3) 2 and 148.8 ° for O[Si(CH3)3] 2 (Barrow, Ebsworth & Harding, 1979).…”

mentioning

confidence: 99%

On the SiOSi angle in 1,2-di-tert-butyl-1,1,2,2-tetraphenyldisiloxane

Karle¹,

Karle²,

Nielsen³

1986

Acta Crystallogr C

View full text Add to dashboard Cite

“…Whereas the Si-O bond to the hexacoordinate Si atom is rather long [170.0(3) pm], this bond lengthening upon pyridine coordination gives rise to a shortening of the second Si-O bond [to 158.0(3) pm], whereas for hexachlorodisiloxane a slightly longer Si-O bond length of 159.2 ± 1.0 pm was reported (results of gas phase electron diffraction analysis). [42] The Si-O-Si angle [149.0 (2) • ] is similar to that of hexachlorodisiloxane (in the gas phase), which was determined to be 146 ± 4…”

Section: Formation Of Siloxane/silylcarbodiimide Xerogels -Cl 3 Si-osmentioning

confidence: 99%

Sol–gel derived Si/C/O/N‐materials: molecular model compounds, xerogels and porous ceramics

Cheng

Lippe

Kroke

et al. 2011

Applied Organom Chemis

View full text Add to dashboard Cite

An electron diffraction determination of the molecular structures of perchlorodisiloxane and methoxytrifluorosilane

Cited by 69 publications

References 16 publications

The crystal and molecular structures of disiloxane (at 108 K) and hexamethyldisiloxane (at 148 K)

The crystal and molecular structures of disiloxane (at 108 K) and hexamethyldisiloxane (at 148 K)

On the SiOSi angle in 1,2-di-tert-butyl-1,1,2,2-tetraphenyldisiloxane

Sol–gel derived Si/C/O/N‐materials: molecular model compounds, xerogels and porous ceramics

Contact Info

Product

Resources

About