Gas-phase Molecular Structures Determined by Electron Diffraction

The task of preparing these annual reports is sometimes tedious but it also provides an opportunity to assess the role played by gas electron diffraction in inorganic chemistry, and to see how the subject is progressing. That there is a continuing need for structural studies in the gas phase is beyond doubt. The numbers of structures reported and papers reviewed have barely changed over the past ten years. In this present chapter, in which we present results published in 1998, we describe nearly sixty structures. Some of these are reanalyses of old data or redeterminations of structures, but the majority are new structures, mainly of compounds which have only recently been synthesised. 

The use of density functional theory calculations is increasing, and at present such calculations should come with a health warning. Within the set of papers reviewed here there are many examples of structures calculated both ab initio and by density functional theory. The results demonstrate well the unpredictability of density functional theory for molecules which are not very similar to others for which its reliability has already been tested. Bond lengths may be long or short, often by 5 pm or even more, and angles are also potentially in error by 3-5 °. We need to be very careful, therefore, when using only the results of density functional theory calculations to restrain or constrain electron diffraction refine- 

Spectroscopic Properties of Inorganic and Organometallic Compounds, Volume 32 The Royal Society of Chemistry, 1999 

As usual we present geometrical parameters of the structural type (rg, r , Tg, r, etc.) reported in the original papers and with the same uncertainties, quoted in parentheses after numerical values. 

Section 3, Group 14 perfluoroadamantane, Me4-hexathia-adamantane, SH4, cyctoSiCl2(CH2)3, CfiHsSiHj, (GeH3)3CH, (GeH3 4C, Me3SnI, 1,3,5-C6H3(SnMe3)3. 

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Nuclear Magnetic Resonance Spectroscopy Nuclear Quadrupole Resonance Spectroscopy Rotational Sp roscopy Characteristic Vibrations of Compounds of Maiit-group Elements Vibrational Spectra of Transition-slement Compounds Vibrational Si ra of Some Co-ordinated Ligands Mossbauer Spectroscopy Gas-phase Molecular Structures Determined by Electron Diffraction. 

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