Subject silicon hydrides

I thank Keith U. Ingold for having introduced me to this subject. When I arrived in Ottawa at the National Research Council of Canada in 1979 for three years postdoctoral work with him, very little was known on the reactivity of silyl radicals. At that time, several papers dealing with kinetics of silyl radicals were published, which allowed the reactivity of silyl radical to be translated into a quantitative base. Special thanks go to David Griller for his collaboration on the initial work on hydrogen donor abilities of silicon hydrides during the late 1980s. 

Over the last few years, silicon hydrides have been introduced as the radical mediators and the intramolecular C — C bond formation (or cyclization) by these reagents has been the subject of numerous publications. 

The silicon hydrides are prepd either by acid decompn of Mg silicide or by redn of SiCl4 with LiAlH4 (Refs 1-4, 12, 14,15, 16 26). Disilane and other higher hydrides have been conveniently synthesized by subjecting SiH4 to a silent electrical discharge (Ref 26, p 175). Prepn of individual silanes of ordn interest are given below... 

The hydrosilylation of alkenes and alkynes catalyzed by transition metal complexes is often accompanied by side reactions such as isomerization, polymerization, and hydrogenation of unsaturated compounds and/or redistribution and dehydrogenation of silicon hydrides as well as reactions in which both substrates take part, such as dehydrogenative silylation (4,13). The latter reaction, which in certain conditions permits direct production of unsaturated silyl compound, has been a subject of intense study over the last two decades. 

Although addition of silicon hydrides to olefins and acetylenes takes place in the presence of a variety of catalysts, chloroplatinic acid ( Speier s catalyst ) is by far the most commonly used catalyst for the reaction. This subject including the reaction mechanism has been well reviewed elsewhere [8]. 

See, for a review of this subject, A. Stock, Hydrides of Boron and Silicon, Cornell University Press, 1933 H. I. Schlesinger and A. B. Burg, Chem. Revs. 31, 1 (1942). 

Silatungstacyclopropane (35) is subject to addition reactions as well. Methanol, H2, and H-TMS all add to the metal-carbon bond. The first two reactions lead to metal hydrides while the last reagent gives a metallasilane. Trimethylphosphine addition to (35) causes attack of cyclopentadienide at silicon and cleaves the silicon-metal bond <90JA6405>. 

Why did I decide to undertake my doctorate research in the exotic field of boron hydrides As it happened, my girlfriend, Sarah Baylen, soon to become my wife, presented me with a graduation gift, Alfred Stock s book. The Hydrides of Boron and Silicon. / read this book and became interested in the subject. How did it happen that she selected this particular book This was the time of the Depression. None of us had much money. It appears she selected as her gift the most economical chemistry book ( 2.06) available in the University of Chicago bookstore. Such are the developments that can shape a career. 

The subject dealt with in this volume is concerned with the analysis of all types of organometallic compounds and includes, where relevant, a discussion of metal hydrides, e.g. hydrides of silicon. 

The chemistry of stable silylenes has been the subject of considerable research since the first isolation of silicocene by Jutzi in the 80s (1). More recently, silylenes stabilized by coordination of a donating ligand on the silicon(II) atom have attracted much attention due to their high reactivity strongly related to the nature of ligands, and we have demonstrated that phosphine-stabilized silylenes display unique properties. Of particular interest, the phosphine-stabilized silicon(II)-hydride 5 immediately reacts with olefins and alkynes via [2-1-1] cycloaddition reactions. In the case of diphenylacetylene, the corresponding pentacoordinate... 

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