Molecular structures of dichloro(dimethyl)germane and trichloro(methyl)germane determined by vapour phase electron diffraction

1977 ◽  
Vol 55 (6) ◽  
pp. 1104-1110 ◽  
Author(s):  
John E. Drake ◽  
J. Lawrence Hencher ◽  
Quang Shen
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Confidence Level ◽  
Systematic Errors ◽  
Vapour Phase ◽  
Molecular Structures ◽  
Electron Diffraction Data ◽  
Geometrical Parameters ◽  
Methyl Group ◽  
Uncertainty Estimates

The molecular structures of dichloro(dimethyl)germane and trichloro(methyl)germane have been determined in the vapour phase by electron diffraction. The principal geometrical parameters for (CH3)2GeCl2 are rg(Ge—Cl) = 2.143 ± 0.004 Å, rg(Ge—C) = 1.928 ± 0.006 Å, [Formula: see text].and [Formula: see text] In the analysis of CH3GeGl3 recently reported values of the rotational constants were combined with the electron diffraction data to give rg(Ge—Cl) = 2.132 ± 0.003 Å, rg(Ge—C) = 1.893 ± 0.010 Å, [Formula: see text] and [Formula: see text]In both cases the methylgermane geometry was assumed for the methyl group [Formula: see text] which was fixed in the staggered configuration with respect to the C2GeCl2 and CGeCl3 frames respectively. Both random and systematic errors were included in the uncertainty estimates, which are believed to be approximately at the 95% confidence level. In the case of (CH3)2GeCl2 the uncertainties in [Formula: see text] were enlarged to four times the least-squares values in order to reflect the difficulty of resolving the Cl … Cl, C … Cl, and C … C distances in the analysis.

The Molecular Structures of Hexamethyldistannane, (CH3)6Sn2, and Dimethylditellurane, (CH3)2Te2, by Gas Electron Diffraction

1990 ◽  
Vol 45 (8) ◽  
pp. 1143-1146 ◽  
Author(s):  
Arne Haaland ◽  
Andreas Hammel ◽  
Hanne Thomassen ◽  
Hans V. Volden ◽  
Harkesh B. Singh ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Molecular Models

Gas electron diffraction data of (CH3)6Sn2 and (CH3)2Te2 are consistent with molecular models of D3 and C2 symmetry and bond distances Sn–Sn = 277.6(3) pm and Te–Te = 268.6(3) pm, respectively.

The Molecular Structures and Conformational Preferences of Simple Molecules Containing Bonds Between a Trivalent Group 15 and a Divalent Group 16 Element: The Molecular Structures of Dimethyl(methylthio)stibane and Dimethyl(methylseleno)stibane, (CH3)2SbECH3 E = S or Se, by Gas Electron Diffraction

1993 ◽  
Vol 48 (8) ◽  
pp. 1065-1068 ◽  
Author(s):  
Arne Haaland ◽  
Hans Peter Verne ◽  
Hans Vidar Volden ◽  
Hans Joachim Breunig ◽  
Sabahittin Gülec
Keyword(s):  
Electron Diffraction ◽  
Dihedral Angle ◽  
Diffraction Data ◽  
Lone Pair ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Conformational Preferences ◽  
Group 15 ◽  
Simple Molecules

Gas electron diffraction data of (CH3)2SbECH3 E = S or Se, show that the predominant conformer is one where the dihedral angle defined by the E–C bond, the Sb–E bond and the presumed direction of the lone pair at the Sb atom falls in the range –45 to +45°. The Sb–S and Sb–Se bond distances are 241.4(8) and 255.5(3) pm, respectively.

scholarly journals Refinement of organic crystal structures with multipolar electron scattering factors

2020 ◽  
Vol 76 (1) ◽  
pp. 92-109 ◽  
Author(s):  
Barbara Gruza ◽  
Michał Leszek Chodkiewicz ◽  
Joanna Krzeszczakowska ◽  
Paulina Maria Dominiak
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Model Fitting ◽  
Molecular Structures ◽  
Electron Diffraction Data ◽  
X Ray Diffraction ◽  
Atom Model ◽  
Mechanical Methods ◽  
Atomic Scattering ◽  
The University

A revolution in resolution is occurring now in electron microscopy arising from the development of methods for imaging single particles at cryogenic temperatures and obtaining electron diffraction data from nanocrystals of small organic molecules or macromolecules. Near-atomic or even atomic resolution of molecular structures can be achieved. The basis of these methods is the scattering of an electron beam due to the electrostatic potential of the sample. To analyse these high-quality experimental data, it is necessary to use appropriate atomic scattering factors. The independent atom model (IAM) is commonly used although various more advanced models, already known from X-ray diffraction, can also be applied to enhance the analysis. In this study a comparison is presented of IAM and TAAM (transferable aspherical atom model), the latter with the parameters of the Hansen–Coppens multipole model transferred from the University at Buffalo Databank (UBDB). By this method, TAAM takes into account the fact that atoms in molecules are partially charged and are not spherical. Structure refinements were performed on a carbamazepine crystal using electron structure-factor amplitudes determined experimentally [Jones et al. (2018). ACS Cent. Sci. 4, 1587–1592] or modelled with theoretical quantum-mechanical methods. The results show the possibilities and limitations of the TAAM method when applied to electron diffraction. Among others, the method clearly improves model fitting statistics, when compared with IAM, and allows for reliable refinement of atomic thermal parameters. The improvements are more pronounced with poorer-resolution diffraction data.

Refinement of Organic Crystal Structure with Multipolar Electron Scattering Factors

2019 ◽  
Author(s):  
Barbara Gruza ◽  
Michał Leszek Chodkiewicz ◽  
Joanna M. Krzeszczakowska ◽  
Paulina Dominiak
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Model Fitting ◽  
Molecular Structures ◽  
Electron Diffraction Data ◽  
X Ray Diffraction ◽  
Single Particles ◽  
Mechanical Methods ◽  
Atomic Scattering ◽  
The University

A revolution in resolution is occurring now in electron microscopy arising from the development of methods for imaging single particles at cryogenic temperatures and obtaining electron diffraction data from nanocrystals of small organic molecules or macromolecules. Near- atomic or even atomic resolution of molecular structures can be achieved. The basis of these methods is the scattering of an electron beam due to the electrostatic potential of the sample. To analyze this high-quality experimental data, it is necessary to use appropriate atomic scattering factors. The independent atomic model (IAM) is commonly used although various more advanced models, already known from X-ray diffraction, can also be applied to enhance the analysis.<br>In this study we present a comparison of IAM and TAAM (Transferable Aspherical Atom Model), the latter with the parameters of the Hansen-Coppens multipole model transferred from the University at Buffalo Databank (UBDB). By this method, TAAM takes into account the fact that atoms in molecules are partially charged and are not spherical. We performed structure refinements on a carbamazepine crystal using electron structure factor amplitudes determined experimentally (Jones et al., 2018) or modeled with theoretical quantum-mechanical methods. The results show the possibilities and limitations of the TAAM method when applied to electron diffraction. Among others, the method clearly improves model fitting statistics, when compared to IAM, and allows for reliable refinement of atomic thermal parameters. The improvements are more pronounced with poorer resolution of diffraction data.<br>

scholarly journals Refinement of Organic Crystal Structure with Multipolar Electron Scattering Factors

2019 ◽  
Author(s):  
Barbara Gruza ◽  
Michał Leszek Chodkiewicz ◽  
Joanna M. Krzeszczakowska ◽  
Paulina Dominiak
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Model Fitting ◽  
Molecular Structures ◽  
Electron Diffraction Data ◽  
X Ray Diffraction ◽  
Single Particles ◽  
Mechanical Methods ◽  
Atomic Scattering ◽  
The University

A revolution in resolution is occurring now in electron microscopy arising from the development of methods for imaging single particles at cryogenic temperatures and obtaining electron diffraction data from nanocrystals of small organic molecules or macromolecules. Near- atomic or even atomic resolution of molecular structures can be achieved. The basis of these methods is the scattering of an electron beam due to the electrostatic potential of the sample. To analyze this high-quality experimental data, it is necessary to use appropriate atomic scattering factors. The independent atomic model (IAM) is commonly used although various more advanced models, already known from X-ray diffraction, can also be applied to enhance the analysis.<br>In this study we present a comparison of IAM and TAAM (Transferable Aspherical Atom Model), the latter with the parameters of the Hansen-Coppens multipole model transferred from the University at Buffalo Databank (UBDB). By this method, TAAM takes into account the fact that atoms in molecules are partially charged and are not spherical. We performed structure refinements on a carbamazepine crystal using electron structure factor amplitudes determined experimentally (Jones et al., 2018) or modeled with theoretical quantum-mechanical methods. The results show the possibilities and limitations of the TAAM method when applied to electron diffraction. Among others, the method clearly improves model fitting statistics, when compared to IAM, and allows for reliable refinement of atomic thermal parameters. The improvements are more pronounced with poorer resolution of diffraction data.<br>

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