A general route for the preparation of organosilanes from silica is described. Depolymerization of silica is easily performed by chelating agents such as catechol in the presence of a base such as sodium methoxide with formation of a monomeric hexacoordinated complex [ S~( O -O~C~H~)~]~-~M + (I). The reaction of an excess of Grignard or organolithium reagent leads to the formation of R4Si or R3SiO-CBH4-(o-OH) depending on the nature of the reagent. Functional organosilanes R3SiX can be prepared in a one-pot reaction from 1. Silane (SiH4) is obtained in quantitative yield under very mild conditions from 1. Interestingly, hypervalent anionic silicon species 1 react efficiently with strong nucleophiles, the products obtained corresponding to the result of a nucleophilic displacement at silicon.

Anyen. Chem. I n / . Ed. Engl. 25 (19861 No. 5 0 VCH Verlagsgesellschafr mbH, 0-6940 Weinheim. 1986 0570-0833/86/0505-0473 $ 02.50/0 Languedoc, Unite Associee C.N.R.

The reactivity of anionic penta-coordinated silicon complexes [RSi(O2C6H4-o)2]−Na+  1 with nucleophilic reagents has been studied. 1 can be reduced to organosilanes RSiH3 by metallic hydrides. Reactions with an excess of Grignard or organolithium reagents (R′MgX or R′Li) gave tetraorganosilanes RSiR′3. When only two molar equivalents of Grignard reagents (R′MgX) or lithium reagents (R′Li) are added to complexs 1 functional silanes RR′2SiX can be prepared.

No abstract

RSiR;: The suspension of 1 in ether was treated with an excess (3.6 equivalents) of organometallic reagent. After the addition, the mixture was refluxed for 1 h and then hydrolyzed with H2S04 (25%). The silane was then extracted as described above.