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29Si NMR spectra of methylphenylcyclotri-and -tetrasilazanes

✍ Scribed by B. D. Lavrukhin; B. A. Astapov; A. A. Zhdanov; G. Engelhardt; H. Jancke

Publisher
John Wiley and Sons
Year
1982
Tongue
English
Weight
281 KB
Volume
18
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

^29^Si NMR spectra of various methylphenyl‐substituted cyclotri‐ and ‐tetrasilazanes, composed of different combinations of the units d = Me~2~SiNH, d^ph^ = MePhSiNH and d = Ph~2~SiNH, have been investigated. For most of the compounds having more than one asymmetric centre, the spectra of both the individual isomers and their mixtures have been studied, and the signals of the individual isomers have been assigned. The effect of a different arrangement of phenyl groups in the rings, and the influence of the stereochemistry of the isomers on the ^29^Si chemical shifts in cyclotri‐ and ‐tetrasilazanes have been studied. The ^29^Si chemical shifts in cyclotrisilazanes are additive and can be represented as the sum of increments corresponding to the number and positions of the phenyl groups in the rings. In these compounds, the spatial structure of the isomers does not exert any noticeable effect on the spectra. On the contrary, chemical shifts are not simply additive in cyclotetrasilazanes: a pronounced stereochemical dependence is apparent.

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