Ambient-condition nano-alumina formation through molecular control

When toluene solutions of the tetrametallic compound, [Al{μ-OEt) ₂AlMe₂}₃] (1), are stirred in air at room temperature, pure amorphous nanoparticulate Al₂O₃ precipitates. The average particle size is 17.7 ± 7.4 nm. The tetrametallic core of 1, having the correct stoichiometry for alumina (2Al ₂O₃) appears to act as a template or nucleating site for the formation of alumina rather than the expected products of formula, AlOOH. The stability of the Al₄O₆ core of 1 was tested by combining it with six equivalents of Ph₃SiOH. This resulted in [Al{μ-OEt)₂Al(OSiPh₃)₂}₃] (2). Upon exposure to air, compound 2 formed the hydroxide derivative [Al{μ-OH)₂Al(OSiPh₃)₂}₃] (3). This demonstrates that the tetrametallic core of 1 is stable to both peripheral derivatization as well as alcoholysis of the internal bridging groups.