The Determination of the Molecular Structure of Bromosilane by Microwave Measurements

Sharbaugh, A. H.; Bragg, J. K.; Madison, T. C.; Thomas, Virginia G.

doi:10.1103/physrev.76.1419

Cited by 25 publications

(2 citation statements)

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“…The microwave spectra of SiH3F (43), SiF3H (44), SiFsCHs (44), SiFaCl (44), and SiFaBr (44) The CSiBr angle in trimethyl bromosilane is 105 ± 4°, considerably less than tetrahedral. This is consistent with the larger than tetrahedral HSiH angle of 111° 20' reported for SiHaBr (42).…”

Section: Structuressupporting

confidence: 91%

“…Silane derivatives.-Complete structures for the symmetrical top mole cules chlorosilane (40,41) and bromosilane (42) have been deduced from their microwave spectra. In SiHsCI, the SiH distance is reported to be 1.50 A, the SiCI distance 2.048 A, and the HSiH angle 110° 57'; in SiHaBr, the SiH distance is 1.57 A, the SiBr distance 2.209 A, and the HSiH angle 111°20', The silicon-halogen distances are all shorter than the sum of the covalent radii and the silicon-hydrogen distances are longer, indicating considerable ionic or double bond character to the SiX bond.…”

Section: Structuresmentioning

confidence: 99%

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Experimental Molecular Structure

Roth¹

1951

Annu. Rev. Phys. Chem.

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The principal sources of information about the structure of molecules in the free state are electron diffraction of gases, spectroscopy in the infrared, Raman and microwave regions, and x-ray diffraction of crystals. The past year has seen a continuation of the trends noted in the previous review by Beach (1). The general structural principles for most small molecules are reasonably well understood, and interest now is directed toward the under standing of variations of bond distances and angles in different molecules and the study of more complicated systems, such as larger molecules and the nature of intramolecular motions.The advances in experimental technique in electron and x-ray diffraction and the striking interpretations of pure rotational spectra in the microwave region are beginning to provide a body of information relating to interatomic parameters where the distances are reliable to 0.01 'A or better and the angles reliable to 30'. Some success is obtained in accounting for the observed inter atomic distances by modifying the sum of the covalent radii (14) with cor rections for ionic or multiple bond character (18), but it is apparent that there is a need for precise data from a largernumberof molecules. Accordingly, much of the work at the present time is concerned with improving experi mental techniques or with redetermining the structures of many molecules by the newer methods.Electron diffraction.-The need for the determination of a larger number of parameters has led many workers in the field of electron diffraction to search for increased sensitivity and objectivity. The early electron diffraction investigations were accomplished by the visual correlation technique, where calculated intensity patterns based on assumed models were compared with the visually observed diffraction pattern. As the complexity of the molecules studied increased and it became necessary to determine a larger number of parameters, it became increasingly difficult to arrive at a unique model. At the present time, many molecules are being reinvestigated and extensive work is being done to increase the accuracy and sensitivity of the experimen tal techniques.Recent papers by . the Karles (2, 3, 4) and Hastings & Bauer (5, 8) con tain detailed discussions of the effects of various experimental factors on the diffraction patterns: the proper design of a gas nozzle for introducing the sample into the electron beam, the effect of finite sampJe size and divergence of the beam, mUltiple scattering, the use of beam stops and rotating sectors, and the response characteristics of photographic emulsions.1 This review is a continuation of that of Beach (1) and covers approximately the year 19 50.

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Section: Structuressupporting

confidence: 91%