Synthesis and Characterization of Amorphous Nanostructured HAlO, a Novel Aluminumoxyhydride

Abstract

A novel material, amorphous nanostructured HAlO, has been synthesized by the reaction of various methylsiloxanes [e.g., (Me2HSi)2O] with the aluminum hydride H3Al·NMe3 in ether or aromatic solvents under mild conditions. Its high surface area of ca. 250 m2/g is due to both its small particle size of approximately 5 nm and its amorphous nanostructure. Its amorphous nature was demonstrated by TEM and XRD studies, and its composition was determined by elemental analysis, 1H and 27Al MAS solid-state NMR spectroscopies, and FT-IR spectroscopy. HAlO is an oxidic material that still contains a reactive aluminum hydride functional group. Prolonged heating at 200−250 °C causes it to slowly decompose to aluminum metal and amorphous Al2O3 without significantly changing the particle size or the BET surface area. This decomposition is accompanied by the loss of hydride and a decrease of the aluminum coordination number from five to four. HAlO reacts readily with protic reagents such as water or alcohols to give bayeri...