Surface organometallic chemistry of germanium: Infrared, CP-MAS ¹³C solid state NMR, and analytical evidence for the formation of highly thermally stable -O-Ge(n-C₄H₉)₃ grafted fragments by reaction of Ge(n-C₄H₉)₃ with the surface of partially dehydroxylated alumina and silica-alumina

Interaction of Ge(n-C₄H₉)₄ complex with partially dehydroxylated α- and η-alumina and silica-alumina surfaces has been investigated by ¹³C CP-MAS NMR, infrared spectroscopy, and analytical methods. At 25 °C, Ge(n-C₄H₉)₄ interacts, via hydrogen bonds, by its butyl ligands, with hydroxyl groups of the surface. At 250 °C, Ge(n-C₄H₉)₄ reacts with the hydroxyl groups to form >X-O-Ge(n-C₄H₉)₃ (X = Si, Al) and 1 mol of butane/mol of grafted germanium. When the complex is grafted on silica-alumina the germanium atom is tetracoordinated, while on alumina it could adopt a tetra- or a pentacoordination. The grafted -O-Ge(n-C₄H₉)₃ fragments exhibit, on both silica-alumina and alumina, extraordinary high thermal stability (until 400 °C in vacuo). This phenomenon had already been observed with ≡SiOGe(n-C₄H₉)₃ grafted on silica.