Nanometals and colloids as catalyst precursors

Abstract

Publisher Summary The reduction of transition metal salts and oxides using hydrotriorganoborates in organic media allows the production of X-ray amorphous nanopowders of metals and alloys under mild conditions. The reduction of TiCl4 with K[BEt3H ] gives an ether-soluble [Ti(0) · 0.5 THF]x, which serves as a catalyst for the hydrogenation of titanium or zirconium sponges and related systems and as a powerful activator for heterogeneous hydrogenation catalysts. The use of tetraalkylammonium hydrotriorganoborates as reducing agents leads to colloidal transition metals in organic phases. These colloids may also be obtained using conventional reducing agents after first reacting the metal salts with the stabilizing tetraalkylammonium halide. Colloidal metals prepared in this way serve as sources for heterogeneous metal catalysts. X-ray powder diffraction measurements have revealed that the metal powders obtained by the deoxygenation of metal oxides are generally nanocrystalline. The preformed metal colloids offer the possibility of obtaining small monodisperse particles of discrete particle sizes on commercially available supports.