Das Isosterenpaar SiO/PN, I. Zur Isosterie von Perchlorcyclosiloxanen und Perchlorcyclophosphazenen. Schwingungsspektren und Röntgenstrukturanalyse von (Cl2SiO)3 und (Cl2SiO)4 / The SiO/PN Isoelectronic Pair, I. Perchlorocyclosiloxanes and Perchlorocyclophosphazenes. Vibrational Spectra and X-Ray Structure Analysis of (Cl2SiO)3 and (Cl2SiO)4

Wannagat, U.; Bogedain, G.; Schervan, A.; Marsmann, H.C.; Brauer, David J.; Bürger, H.; Dörrenbach, F.; Pawelke, G.; Krüger, Carl; Claus, Karl-Heinz

doi:10.1515/znb-1991-0712

Cited by 23 publications

(6 citation statements)

References 10 publications

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“…The electronegative chlorine or bromine ligands in 5a and 5b result in an electron withdrawal from the silicon atoms, leading to a strong shortening of the adjacent Si-O-bonds. In 5a, the Si-O bond lengths of the chlorine substituted silicon atoms (mean: 1.586(7) Å) are in average similar to those found in octachlorotetrasiloxane (Cl 2 SiO) 4 (mean: 1.584(9) Å) [3]. Although we expected longer Si-O distances in the bromine derivative 5b due to lower electronegativity of the bromine atom in comparison to chlorine (E.N.…”

Section: Discussion Of the Structuressupporting

confidence: 67%

“…Whereas in the eight-membered siloxane rings 6 and 7 the variation of the dihedral angles Si-O-Si-O and O-Si-O-Si is remarkable (6: 3.6-34.6°, 7: 2.5-18.4°) and follow the trend that eight-membered siloxane rings differ from the planarity in contrast to planar six-membered siloxane rings [3], the bis(amino)-chloro derivative 5a (variation of dihedral angles: 4.4-8.5°) and the bis(amino)-bromo deriva- tives 5b (variation of dihedral angles: 0.4-4.3°) can be considered as almost planar. All molecules 5a, 5b, 6 and 7 have crystallographic C i symmetry and deviate in the case of 5a and 5b (not considering the tert-butyl groups) only negligibly from D 2h , while in 6 and 7 the twist within the eight-membered rings is more remarkable.…”

Section: Discussion Of the Structuresmentioning

confidence: 87%

“…We were interested to synthesise by a versatile step-bystep route Si n O n cycles with inorganic substituents at silicon presenting different centres of reactivity to facilitate an exchange with other chemical groups. In contrast to a considerable number of reports on cyclosiloxanes with organic groups, such inorganic representatives are rare [3][4][5].…”

Section: Introductionmentioning

confidence: 81%

“…Generally, the Si-O-Si angles in cyclotetrasiloxanes show a large variation according to the flexibility of Si-O-Si-O chains and may differ by more than 10° [20][21][22][23][24]. For example, in octachlorocyclotetrasiloxane, the values range from 154.5°to 165.2° [3]; this effect is normally attributed to the packing of the molecules in the solid state. In the present chlorine and bromine derivative 5a and 5b, the angle differences are relatively small (5a: 159.94(2)°to 163.36(3)°, 5b: 158.0(4)°to 166.5(4)°).…”

Section: Discussion Of the Structuresmentioning

confidence: 99%

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Selective synthesis of eight-membered siloxane rings with different substituents on the silicon atoms

Veith

Rammo

Huppert

et al. 2003

Comptes Rendus. Chimie

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The selective synthesis of eight-membered silicon-oxygen rings of the general formula (R 2 Si) 2 (R' 2 Si) 2 O 4 can be achieved using the auxiliary reagent hexabutyldistannoxane. In a first step, the cycles [CH 2 -N(R)] 2 SiCl 2 [R = tBu (1), Ph (2)] are reacted with the double molar amount of hexabutyldistannoxane to form [CH 2 -N(R)] 2 Si(OSnBu 3 ) 2 3 (R = tBu) and 4 (R = Ph). The syntheses are carried out without any solvent. The distannoxosilanes 3 and 4 are transformed to the eight-membered siloxane rings 6)} using either SiCl 4 , SiBr 4 or Cl 2 SiMe 2 as reactants at ambient temperature. The selective cleavage of the silicon-nitrogen bonds in 6 by addition of a solution of HCl in tetrahydrofuran leads to the chloro-and methyl-substituted cyclotetrasiloxane (Me 2 Si) 2 (Cl 2 Si) 2 O 4 (7). The new cyclotetrasiloxanes 5-7 have been characterised by spectroscopic methods as well as by single crystal X-ray analyses, revealing Si 4 O 4 eight-membered cycles with different substituents on the silicon atoms. Depending on the substitution pattern at silicon atoms, varying Si-O bonds and angle are found.

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Section: Discussion Of the Structuressupporting

confidence: 67%

Section: Discussion Of the Structuresmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 81%

Section: Discussion Of the Structuresmentioning

confidence: 99%

See 2 more Smart Citations

Selective synthesis of eight-membered siloxane rings with different substituents on the silicon atoms

Veith

Rammo

Huppert

et al. 2003

Comptes Rendus. Chimie

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“…The reaction of SiCl 4 with O 2 is of great technological importance for the chemical vapor deposition (CVD) of solid SiO 2 films used in the microelectronics industry and synthesis of the ceramic powders. − The basic reaction occurs when the mixture of O 2 with SiCl 4 , in a tube of about 30 cm length, is heated above 1000 °C. , However, in the temperature range of 800−1000 °C, the resulting product consists of a multitude of chlorosiloxanes of the general formula Si x O y Cl z . , These chlorosiloxanes have a variety of shapes and sizes ranging from chains and rings to oligocyclic and polycyclic shapes. A large number of chlorosiloxanes were identified by mass spectrometry. − These chlorosiloxanes are intermediate compounds formed in the course of the reaction because of the partial replacement of Cl atoms in SiCl 4 by oxygen atoms.…”

Section: Introductionmentioning

confidence: 99%

Reaction Mechanism of Chlorosiloxane Ring Formation from SiCl₄ and O₂

2002

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The formation of the chlorosiloxane ring (Cl 2 SiO) 2 from the reaction of SiCl 4 with O 2 has been studied using density functional theory (DFT). Geometries of reactants, intermediates, transition states, and products were fully optimized, and the relative energies of the stationary points and all of the transition states were calculated on the B3LYP/6-311G* level. The initial reaction of O 2 with SiCl 4 starts on the triplet surface with the insertion of O 2 in SiCl 4 . This will loosen one Cl atom, and a barrier of 56.6 kcal/mol must be overcome. In the next step Cl 2 is eliminated and the cyclic-Cl 2 SiO 2 is formed. The latter reacts with SiCl 4 , which involves a barrier of 76.0 kcal/mol. This process leads to the formation of a low-lying intermediate Cl 2 SiO(OCl)SiCl 3 . The intermediate proceeds under elimination of Cl 2 to the product (Cl 2 SiO) 2 ring over a barrier of 71.3 kcal/ mol. This study also shows that the formation of the Cl 3 SiO radical is found to be energetically more favorable than that of Cl 2 SiO. This can lead to the growth of larger chlorosiloxanes.

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