Electron diffraction study of uranium trichloride

Institute for High Temperatures, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 31, No. 6, pp. 152–153, November–December, 1990.     

An electron diffraction study of the structure of 1,1,2-trichloroethane in the gas phase

The molecular structure of 1,1,2-trichloroethane has been determined by gas phase electron diffraction. The molecule is asymmetric. The geometrical parameters (r_a structure) are: r(C-Cl) 1.776 Å; r(C-H) 0.98 Å; ∠(C-C-Cl) 107°; ∠(Cl-C-Cl) projected along the C-C bond 116°; dihedral angle (Cl-C-C-Cl) 75°. The parameters ∠(C-C-H) 102° and the projected (H-C-H) angle 136° are inaccurate. The structure is rather insensitive to the r(C-C) value, which is unusually long, 1.56 to 1.58 Å.     

An electron diffraction study of the molecular structure of methylthionformate in the gas phase

The molecular structure of methylthionformate in the gas phase has been determined by electron diffraction. The CS and O-CH₃ bonds are nearly eclipsed. The dihedral angle between the C-O-C and O-C-S plane is 15.8 ± 2.5°.     

The molecular structure of tetramethoxymethane in the gas phase: an electron diffraction study

The electron diffraction study of tetramethoxymethane showed that in the gas phase the molecule has S₄ symmetry, flattened along the S₄ axis. Central and peripheral C-O bond lengths are different, consistent with considerations based on the anomeric effect. Comparison is made with ab initio calculations on methanediol. The geometrical parameters (r_g(1) structure) are: central C-O bond 1.395 Å; peripheral C-O bond 1.422 Å; C-H bond 1.11 Å; O-C-O angle bisected by the S₄. axis 114.7°; C-O-C angle 114.0°; O-C-H angle 111.9°; methoxy torsional angle 63.1°; methyl torsional angle 48.5°.     

The molecular structure of tetramethoxysilane in the gas phase,an electron diffraction study

The molecular structure of tetramethoxysilane was determined in the gas phase by electron diffraction. The molecule has S₄ symmetry, slightly flattened along the axis. The SiO bonds are shorter than in methylsilylether, demonstrating the effect of electronegative substituents on the Si atom. The geometrical parameters (r_a structure) are: Si-O bond 1.613 Å; C-O bond 1.414 Å; C-H bond 1.12 Å; O-Si-O angle bisected by S₄ axis 115.5°; Si-O-C angle 122.3°; O-C-H angle 111°; methoxyl torsional angle 64°; methyl torsional angle 60°.     

A quantum-chemical and gas phase electron diffraction study of the structure of formylphosphine and acetyldimethylphosphine

The equilibrium geometry and energy and structural changes accompanying inversion motion in the phosphorus fragment and acyl group internal rotation in the H₂PCHO and Me₂PCMeO molecules were calculated by the MP2(full) method using basis sets from 6–31G(d, p) to 6–311G(3df, 2p). The structure of Me₂PCMeO was determined by electron diffraction using the dynamic model of acyl group internal rotation based on the quantum-chemical potential function of torsional motion. Acylphosphines have amide-type equilibrium conformations with acyl groups rotated through ∼100° from their orientation in the C=O/PX₂ anti- form, where X = H, Me (C ₁ symmetry). Considerable pyramidality of the phosphorus fragment distinguishes the equilibrium structures of acylphosphines from amides with a planar molecular frame (C _s symmetry). The r _h1 geometric parameters of the Me₂PCMeO molecule determined by electron diffraction closely agree with quantum-chemical estimates for the equilibrium configuration.     

Bonding properties of bicyclopropylidene: gas phase electron diffraction study and X-ray crystal structure analysis

The C=C double bond length in bicyclopropylidene (1) was found to be 131.4(1) and 130.4(8) pm by electron diffraction at 20° and X-ray diffraction at −40°C respectively. This value is in remarkable agreement with that obtained by molecular mechanics calculations; it is significantly shorter than the double bond in normal olefins.