²⁹Si NMR investigation of Si-alkylsubstituted 1,3,5-trisilacyclohexanes

²⁹Si 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.