The interaction of boron halides with 1,1,3,3-tetramethyl-1,3-disilacyclobutane

The exothermic reaction of BX₃ (X = F, Cl, Br) with 1,1,3,3-tetramethyl-1,3disilacyclobutane (I) gave the ring-cleavage product XMe₂SiCH₂Me₂SiCH₂BX₂ (II) in almost quantitative yield. The order of activity was BBr₃ > BCl₃ > BF₃. Heating compounds of structure II at 180°C for 40 h did not affect IIa (X = F) but caused a complete rearrangement of IIc (X = Br) to BrMe₂SiCiH₂MeBrSiCiH₂BMeBr (IIIc). Compound IIb (X = Cl) was incompletely (65%) converted to ClMe₂SiCH₂MeClSiCH₂BMeCl (IIIb) under the stated conditions. It was concluded that the thermal rearrangement most likely proceeded by an intramolecular mechanism since only one isomer was found.     

Transformation of 1,1,3,3-tetramethyl-1,3-disilacyclobutane in presence of aluminum chloride

Conclusions The reaction of equimolar amounts of 1,1,3,3-tetramethyl-1,3-disilacyclobutane and aluminum chloride gives tetramethylsilane and a mixture of linear and cyclic silmethylene compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 953–955, April, 1975.     

Transformations of 1,1,3,3-tetramethyl-1,3-disilacyclobutane in the presence of zirconium tetrachloride

Conclusions One of the possible pathways for the catalytic decomposition of 1,1,3,3-tetramethyl-1,3-disilacyclobutane in the presence of zirconium tetrachloride is the insertion of a dimethylsilaethylene intermediate into the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1917–1919, August, 1985.The authors express their gratitude to A. I. Mikaya for taking the mass spectra.     

Metathesis of allyl cyanide in the presence of a catalytic system containing tungsten hexachloride and 1,1,3,3-tetramethyl-1,3-disilacyclobutane

Conclusions The metathesis of allyl cyanide was carried out by the action of a catalytic system containing tungsten hexachloride by 1,1,3,3-tetramethyl-1,3-disilacyclobutane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 920–921, April, 1988.     

Electron diffraction study of molecular structure of mebicar

The structure of the mebicar molecule has been studied by gas-phase electron-diffractometry using quantum chemical calculations. An eclipsed conformation along the C-C bond (torsion angle ?(H-C-C-H) = 10°) and flattened semi-chair conformations of cyclic fragments have been found. The bond lengths (r _g ) and angles (∠α) show the following average values: r(C-C) 1.576(3) Å, r(C-N) 1.460(3) Å, r(C(O)-N) 1.390(4) Å, r(C=O) 1.211(5) Å, r(C-H) 1.090(5) Å, ∠CCN 103.0(5)°, ∠CNC(O) 112.2(1)°, ∠CNC 122.4(1)°. The dihedral angle between the cyclic fragments is 116.6°.     

Electron diffraction study of the thionyl fluoride molecular structure

The electron diffraction study of thionyl fluoride yielded the following geometrical parameters (r_a structure): S-O 1.420±0.003 Å, S-F 1.583±0.003Å, O-S-F 106.2±0.2° and F-S-F 92.2±0.3°. The average structure (r_α°) is also given. Some of the variations in the molecular geometries of SOX₂ and SO₂X₂ molecules (X = F or Cl) involving the valence shell electron pair repulsion theory are discussed.     

Electron diffraction study on the molecular structure of methyltrimethoxysilane

The electron diffraction data for methyltrimethoxysilane are consistent with a C₃ symmetry model, the predominant forms of which have rotational angle(s) between 100 and 155° around the SiO bond (the anti conformation of the CSiOC chain would respond to 0°). There is probably large amplitude motion around the SiO bonds. The following bond lengths and bond angles were determined: r_a(CH) 1.093 ± 0.005, r_a(SiC) 1.842 ± 0.013, r_a(SiO) 1.632 ± 0.004, r_a(OC) 1.425 ± 0.004 », ∠CSiO 109.6 ± 0.5°. and ∠SiOC 123.6 ± 0.5°.     

Electron diffraction study of the molecular structure of cesium metaborate

The molecular structure of cesium metabomte is studied by gas phase electrvn diffruction. The molecule has C_π symmetry with mean intemuclear distances (T_exp= 1080(10) K) R_g(Cs-O) = 269.2(15) pm, R_g(CS...B) = 360(6) pm, α_gα_g(CsOB) = 125(1)°. It is found that the deformation frequency V(CsOB) = 57(5) cm⁻¹. Translated from Zhumal Struktumoi Khimii, Vol. 41, No. 1, pp. 67-73, 2000.     

Electron diffraction study of the trichloromethyltrichlorogermane molecular structure and estimation for torsional barrier

The molecular geometry (in terms of r_a and r_g internuclear distances) and mean amplitudes of vibration of CCl₃GeCl₃ have been determined by electron diffraction. The bond lengths are similar to those found in analogous molecules. Although bond angles of unambiguous physical definition have not been determined it is established that the carbon and germanium bond configurations deviate little from the regular tetrahedral arrangement. The molecule performs large amplitude motion around the carbon-germanium bond. The torsional barrier was estimated to be 1.1 kcal mole^?1 using J. Karle's method [8].     

A gas-phase electron diffraction study of the molecular structure of 1,1-difluoroethane

The molecular structure of 1,1-difluoroethane has been studied using gas-phase electron diffraction data collected on the Balzers KDG2 instrument. Effective least-squares refinement of the geometry was achieved with fixed values for vibrational amplitudes transferred from normal coordinate calculations on related molecules. In subsequent calculations, in which several amplitudes were also allowed to refine, only minor changes were noted. The refinements yielded the following main geometrical parameters (r_avalues with e.s.d. in parentheses): C—C = 1.498(4) Å, C—F = 1.364(2) Å, C—H(mean) = 1.081(3) Å, ∠CCH(mean) = 111.0(7)°, ∠CCF = 110.7(3)°, ∠FCF = 107.4(5)°. Dependent angles are ∠FCH = 108.5(8)° and ∠HCH = 107.9(7)°.     

Electron diffraction study on the molecular structure of methane sulphonyl fluoride

The molecular structure of methane sulphonyl fluoride in the vapour state was studied by electron diffraction. Assuming a value of 2.480A?for the distance between the oxygen atoms from a microwave determination, the following geometrical parameters (r_a structure) have been obtained: r(C-H) = 1.093±0.010Å, r(S-O) = 1.410±0.003Å, r(S-F) = 1.561 ±0.004Å, r(S-C) = 1.759±0.006Å, ∠F-S-C = 98.2±1.5°, ∠-S-F = 106.2±0.4°, ∠-O-S-O = 123.1 ±1.5° and ∠H-C-H = 112.9±1.9°. All the observed variations in the molecular geometries of (CH₃)₂SO₂, CH₃SO₂Cl, CH₃SO₂F and SO₂F₂ may be accounted for by the valence shell electron pair repulsion theory. It is particularly advantageous to combine electron diffraction and microwave data in studying sulphone molecular geometries.     

Electron diffraction study of the molecular structure of gaseous 1,1-dibromo-3,3,5,5-tetramethyl-1-stanna-3,5-disila-4-oxacyclohexane,Br2Sn(CH2SiMe2)2O

The molecular structure of gaseous Br₂Sn(CH₂SiMe₂)₂O was studied by electron diffraction. The six-membered ring has a chair conformation whereas the entire molecule possessesC _s symmetry. The existence of a boat conformer cannot be completely excluded. The results of theoretical calculations for a twisted-boat conformation are at variance with the experimental data. Steric strain caused by mutual repulsion of the two axial methyl groups is reduced to the tilt of the Me₂Si fragments in opposite directions. This results in an increase (up to 26°C) in the angle formed by the bisector of the C_M-Si-C_M angle with the C_cSiO plane. The main geometrical parameters are as follows:r _g (Å): Si-O 1.708(20); Si-C_M 1.862(20); Si-C_c 1.882(9); Sn-C 2.108(26); Sn-Br 2.456(3); C-H 1.099(30); (degr.): C-Sn-C 105(2); Br-Sn-Br 107.9(1.2); Si-O-Si 129.6(3); C_M-Si-C_M 112; Si-C-H 113 (fixed value in accordance with experiment); C_c-Si-O 107(2); Sn-C-Si 109(2); torsion angles: (Si-C) 52(2); (Si-O) 62(1); (C_c-Sn) 54(1). The average amplitudes were fixed at the values calculated from the force field. Structural parameters of molecules with similar structures were analyzed and compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 384–387, February, 1993.     

Electron diffraction and quantum-chemical study of the molecular structure of 2-chlorobenzenesulfonyl chloride

The molecular structure of 2-chlorobenzenesulfonyl chloride was studied by electron diffraction and quantum-chemical (2/6-31G**, B3LYP/6-311++G**) methods at 337(3) K. Only one (C ₁) conformer was found in the gas phase. The following structural parameters were obtained: r _h1(C-H)_av = 1.105(6) Å, r _h1(C-C)_av = 1.398(3) Å, r _h1(C-S) = 1.783(11) Å, r _h1(S=O)_av = 1.427(3) Å, r _h1(S-Cl) = 2.048(4) Å, r _h1(C-Cl) = 1.731(9) Å, ∠(C-S=O1) = 109.9(8) °, ∠(C-S=O2) = 106.9(8) °, ∠(Cl1-S-O1) = 107.3(4) °, ∠(Cl1-S-O2) = 106.4(4) ∠, ∠C-S-Cl = 102.1(6) °, ∠O=S=O = 122.3(11) °. The C2-C1-S-Cl1 torsion angle that defines the position of the S-Cl bond relative to the plane of the benzene ring was 69.7(8) °. The B3LYP/6-311++G** calculated barriers of internal rotation of the sulfonyl chloride group were V ₀₁ = 9.7 kcal/mol and V ₀₂ = 3.6 kcal/mol.     

Electron diffraction study of the molecular structure of WO2F2

The saturated vapor over solid W ₂ O ₄ F has been studied by electron diffractometry. Structure analysis was fulfilled assuming complex composition of the vapor. It has been established that at T=1043±30 K the vapor consists of WO ₂ F ₂ and WOF ₄ molecules in amounts of 90 and 10 more % respectively. There are two alternative models describing the geometrical structure of the WO ₂ F ₂ molecule (C _2v symmetry) which fit experimental data equally well. In one model, the valence OWO angle is greater than the FWF angle, while in the other, the inverse relation is observed.Ivanovo State University. Moscow Mendeleev Chemical Engineering Institute. Ivanovo Chemical Engineering Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 3, pp. 41–46, May–June 1993.Translated by L. Smolina     

Metathesis of functional derivatives of olefins by the action of the WC16-1,1,3,3-tetramethyl-1.3-disilacyclobutane catalytic system

A study was carried out on the metathesis of esters of unsaturated carboxylic acids and nitriles by the action of the WC1₆ -1,1,3,3-tetramethyl-1,3- disilacyclobutane catalytic system. The possibility of efficient homometathesis and cometathesis with-olefins and allyltrimethylsilane was demonstrated for ethyl 4-pentenoate and ally1 cyanide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 172–176, January, 1990.