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29 Si NMR Investigation of Si‐alkylsubstituted 1,3,5‐Trisilacyclohexanes
Author(s) -
Arnason Ingvar
Publication year - 1999
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/(sici)1521-3749(199901)625:1<97::aid-zaac97>3.0.co;2-h
Subject(s) - substituent , chemistry , alkyl , ring (chemistry) , stereochemistry , crystallography , nmr spectra database , spectral line , physics , organic chemistry , astronomy
29 Si NMR spectra of 29 Si‐alkylsubstituted derivatives of 1,3,5‐trisilacyclohexanes have been recorded and analyzed. A systematic preparation of alkyl derivatives with mixed substituents made it possible to evaluate substituent‐induced chemical shift (SCS) values for the ring silicon atoms in α and γ position. It is found that the equatorial α‐effect increases in the order Me < Et < i‐Pr < t‐Bu. For the alkyl groups Me, Et, and i‐Pr the axial α‐effect is similar in magnitude to the α e ‐effect. Axial SCS values for the t‐Bu group are not accessible because chair conformations with an axial t‐Bu group are energetically unfavourable and escape into a twisted boat form. The observed γ‐effects exhibit the γ gauche ‐effect for axial substituents as known from compounds with a pure carbon framework.