Ketone-Assisted Alkoxysilane Condensation to Form Siloxane Bonds.

Siloxane bond formation represents a fundamental reaction central to both silicone chemistry and its technological applications. This paper presents a novel ketone-assisted process for the condensation of alkoxy-functional silanes catalyzed by a cationic Ge(II) complex stabilized by pentamethylcyclopentadiene CpGe(II). This process leads to the formation of siloxane bonds, with dialkoxy ketal as a byproduct. Unlike the analogous reaction involving aldehydes, the ketone-assisted process is reversible, resulting in the formation of a mixture of alkoxy-functionalized silane or siloxane, along with the corresponding disiloxane product. Additionally, the introduced ketone underwent only partial conversion to the corresponding ketal. Furthermore, it was demonstrated that the siloxane bond could be cleaved to form alkoxysilane in the presence of the ketal and a cationic CpGe(II) complex acting as a catalyst.