The molecular structure of 1,1-dichloro-1-silacyclo-hexane and of 1,1-dimethoxy-1-silacyclohexane in the gas phase, an electron diffraction study

The molecular structure of 1,1-dichloro-1-silacyclohexane (DCSC) and of 1,1-dimethoxyl-silacyclohexane (DMSC) has been determined by gas phase electron diffraction. Starting values for the vibrational parameters were obtained from force field calculations.

Both molecules are in the chair conformation with a flattening in the vicinity of the silicon atom, which is most pronounced in the dichloro-compound. Disregarding the substituents the title compounds show C_s-symmetry. In DMSC the gem-dimethoxy grouping is in the sc, sc conformation in accordance with the anomeric effect.

A comparison is made between the experimentally found geometries with predictions of molecular mechanics calculations based on two available force fields.     

Molecular structure and conformational composition of gaseous 1,1-dichloro-2-bromomethyl-cyclopropane and 1,1-dichloro-2-cyanomethyl-cyclopropane as determined by electron diffraction

The molecular structure of the title compounds have been investigated by gas-phase electron diffraction. Both molecules exist as about equal amounts of the two gauche conformers. There is no evidence for the presence of a syn conformer, but small amounts of this form cannot be excluded. Some of the important distance (r_a) and angle (∠_α) parameters for 1,1-dichloro-2-bromomethyl-cyclopropane are: r(CH) = 1.095(19) Å, r(C₁C₂) = 1.476(11) Å, r(C₂C₃) = 1.517(31) Å, r(CCH₂Br) = 1.543(32) Å, r(CCl) = 1.752(6) Å, r(CBr) = 1.950(13) Å, ∠CCBr = 110.5(1.9)°, ∠ClCCl = 111.9(6)°, ∠CCC = 117.5(1.3)°, σ₁ (CC torsion angle between CBr and the three-membered ring for gauche-1) = 116.2(5.6)°, σ₂ = −132.7(7.6). For 1,1-dichloro-2-cyanomethyl-cyclopropane the parameter values are: r(CH) = 1.101(16) Å, r(C₁C₂) = 1.498(9) Å, r(C₂C₃) = 1.544(21) Å, r(C₂C₄) = 1.497(33) Å, r(CCN) = 1.466(26) Å, r(CN) = 1.165(8) Å, r(CCl) = 1.754(5) Å, ∠CCCN = 113.7(2.0)°, ∠CCC = 122.8(1.6)°, ClCCl = 112.5(4)°, σ₁ = 113(13)°, σ₂ = −124(10)°.     

Electron diffraction study of the structure the NbBr4 molecule

The structure of the NbBr₄ molecule is studied in synchronous electron diffraction and mass spectrometry experiments. Gaseous niobium tetrabromide is synthesized in the course of the experiment during the interaction of niobium chips with bromine at 496°C. Analysis of the geometrical models of the NbBr₄ molecules of C_2v, C_3v, D_2d, and T_d symmetries shows that the tetrahedral model is preferable. The thermally averaged parameters of the effective configuration of the NbBr₄ molecule are as follows: r_g(Nb?Br)=2.418(5) Å, l(Nb?Br)=0.074(2) Å, r_g(Br?Br)=3.921(16) Å, l(Br?Br)=0.271(12) Å, δ(Br?Br)=0.027(18) Å.     

Electron diffraction study of structure of iron trifluoride molecule

Ivanovo Chemical Technology Institute. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 4, pp. 62–67, July–August, 1991.     

Electron diffraction study of the structure of the NbOF3 molecule

Simultaneous electron diffraction and mass spectrometric study of vapor over hydrolyzed NbF₅ was carried out. Conditions providing the presence of niobium oxytrifluoride in the gas phase have been revealed, and structural parameters of the NbOF₃ molecule, corresponding to the r_α configuration of C_3v symmetry, have been determined: r_α(Nb=O) 1.688(7), Å; r_α(Nb-F) 1.861(4) Å; r_α(O-F) 2.857(23) Å; r_α(F-F) 3.079(22) Å; ∠_α(O-Nb-F) 107.1(1.5)^o; ∠_α(F-Nb-F) 111.6(1.4)^o. Ivanovo State Chemical Technological Academy. Ivanovo State University. Translated fromZhumal Struktumoi Khimii, Vol. 37, No. 4, pp. 708–715, July–August, 1996. Translated by L. Smolina