Gold-Induced MgCl2 Reduction by AlEt3. Surface Science Study of a Novel Reaction and Its Potential Application in Ziegler−Natta Catalysis

A novel surface reaction for the reduction of MgCl 2 by AlEt 3 in the presence of Au is reported. MgCl 2 submonolayer and multilayer films are prepared by gas-phase deposition over polycrystalline gold in UHV. When submonolayer MgCl 2 films are exposed to liquid AlEt 3, the halide is reduced, with the formation of Mg clusters or islands, covered with hydrocarbon fragments. The reduction of the halide at the Au surface is faster, and more complete, when MgCl 2 and AlEt 3 molecular beams are simultaneously directed at the metal surface. The reduced Mg surface reacts promptly with gas-phase TiCl 4, and a TiCl 2 /TiCl 4 film is thus deposited. This experiment demonstrates the feasibility of producing a MgCl 2 support with a large fraction of its surface capable of TiCl 4 chemisorption. The possibility of synthesizing Ziegler−Natta catalysts with a large density of active sites is discussed.