title: Amorphous silicon: new insights into an old material.
abstract: Amorphous silicon is synthesized by treating the tetrahalosilanes SiX4 (X=Cl, F) with molten sodium in high boiling polar and non-polar solvents such as diglyme or nonane to give a brown or a black solid showing different reactivities towards suitable reagents. With regards to their technical relevance, their stability towards oxygen, air, moisture, chlorine-containing reaction partners RCl (R=H, Cl, Me) and alcohols is investigated. In particular, reactions with methanol are a versatile tool to deliver important products. Besides tetramethoxysilane formation, methanolysis of silicon releases hydrogen gas under ambient conditions and is thus suitable for a decentralized hydrogen production; competitive insertion into the MeO-H versus the Me-OH bond either yields H- and/or methyl-substituted methoxy functional silanes. Moreover, compounds, such as Men Si(OMe)4-n (n=0-3) are simply accessible in more than 75 % yield from thermolysis of, for example, tetramethoxysilane over molten sodium. Based on our systematic investigations we identified reaction conditions to produce the methoxysilanes Men Si(OMe)4-n in excellent (n=0:100 %) to acceptable yields (n=1:51 %; n=2:27 %); the yield of HSi(OMe)3 is about 85 %. Thus, the methoxysilanes formed might possibly open the door for future routes to silicon-based products.
authors: Institut für Anorganische Chemie, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany), Fax: (+49) 69-798-29188.
authors: Natalie
authors: N
authors: Spomer
authors: Sven
authors: S
authors: Holl
authors: Larissa
authors: L
authors: Zherlitsyna
authors: Fariba
authors: F
authors: Maysamy
authors: Andreas
authors: A
authors: Frost
authors: Norbert
authors: N
authors: Auner
keywords: alcohols; chlorine; reduction; silanes; silicon