Azasilatrane methanolysis pathways: stereoelectronic influences

Abstract

Trigonal-bipyramidal azasilatranes of the type ZSi(NHCH2CH2)3N (Z = H, Me, OEt) solvolyze in MeOH to give N(CH2CH2NH2)3 (tren) and ZSi(OMe)3. Whereas intermediates in this reaction are not detected, ZSi[N-(SiR3)CH2CH2]3N species afford detectable intermediates of the type ZSi[N(SiR3)CH2CH2]n(NHCH2CH2)3-nN (n = 1, 2) before complete conversion to tren and ZSi(OMe)3 occurs. In cases where steric encumbrances weaken the Si-Nax bond in these molecules, monocyclic intermediates are detected. In contrast, methanolysis of HSi[N(BMe2)CH2CH2]3N gives N(CH2CH2NHBMe2)3 (and HSi-(OMe)3), which in the presence of CD3OD gives (CD3O)nSi(OMe)4-n and the novel adduct N-[CH2CH2NHD·B(OCD3)Me2]3. The possible steric and electronic influences of the equatorial substituents on the solvolysis pathways are discussed.