Zur reaktivität aminosubstituierter disilane und germylsilane gegenüber trifluormethansulfonsäure

Primary Amine Functionalization of Alkoxysilanes: Synthesis, Selectivity, and Mechanistic Insights

We report a highly selective substitution of silicon-bound methoxy groups by primary lithium amides. This unusual reactivity is possible because of the formation of particularly stable lithium methoxide, which compensates for the decreased Si-N bond enthalpy compared to Si-O bonds. In contrast to substitution reactions on halosilanes, highly selective monosubstitutions under mild conditions are possible, even in the presence of further reactive methoxy groups. A combination of experiments and density functional theory calculations was carried out in order to get an extensive understanding of the reaction. The calculations reveal a possible reaction mechanism with considerably low activation barriers and the entry of the nucleophile to be the rate-determining step. The low activation energies allow for the substitutions to be carried out at low temperatures, therefore preventing side reactions from occurring. The presented investigations expand the view of fundamental transformation processes on silicon and give access to a wide variety of functionalized silicon-based building blocks for various fields of chemistry.

Selective Synthesis and Derivatization of Germasilicon Hydrides

Mixed Si/Ge hydrides SixGeyHz are valuable precursors for the deposition of binary Si-Ge alloys. This work describes the synthesis and full characterization of the previously unknown germaisotetrasilane Ph3GeSi(SiH3)3 (2) on a multigram scale from the reaction of the lithium silanide LiSi(SiH3)3 with Ph3GeCl. The stability of the Si-Ge bond in 2 versus electrophiles and nucleophiles has been investigated with the primary aim of developing new approaches to mixed sila-H-germanes (H3Ge)xSi(SiH3)4-x. With 1 equiv of MeLi, 2 reacted cleanly under cleavage of one Si-Si bond to give Ph3GeSi(SiH3)2Li, which is a valuable synthon for further derivatization. In contrast, the dephenylation reaction of 2 with 1 or 2 equiv of CF3SO3H/iBu2AlH proceeded much less selectively and afforded the desired Ph/H-germasilanes Ph2HGeSi(SiH3)3 and PhH2GeSi(SiH3)3 along with considerable amounts of Si-Ge scission products.

One-step conversion of methoxysilanes to aminosilanes: a convenient synthetic strategy to N,O-functionalised organosilanes

A straightforward substitution of silicon-bonded methoxy groups by a lithium amide leading to aminomethoxysilanes is presented. DFT calculations allow thermodynamic insight into the unusual equilibrium conditions. The applicability of N,O-functionalised organosilanes is exemplified by the convenient synthesis of an unsymmetrical methoxydisiloxane.