Alkali metal trimethylsilanolates

The Si-NMR and IR data of the alkali metal hydridotrimethylsiloxysilanolates 17-21 are shown in Table 3. The compounds 6-8, 14-17 and 21 have been synthesized by standard procedures as comparison substances for the investigations of the reaction behavior of the silyloxysilanes towards alkali metal trimethylsilanolates. 

Reactions of Siloxysilanes with Alkali Metal Trimethylsilanolates.424... 

The condensation reactions of silanols are catalyzed by bases [19, 25-27, 66, 69]. Grubb found that the condensation of trimethylsilanol in methanol was catalyzed by alkali metal salts of hydroxides [19]. The rate of condensation was dependent on the concentration of hydroxide anion. The type of alkali metal... 

The catalyst in these studies was a tetramethylammonium silanolate. [SiOH]o represents the initial trimethylsilanol concentration, and ky, and kc are rate constants. Use of alkali metal silanolates complicated the kinetics because of the self-association outlined in reaction 10. A reaction scheme consistent with the rate equation is given by equations 25-27. 

For alkali metal t-butoxides and trimethylsilanolates the heterocubane structure is found for the heavier alkali metals potassiiun, rubidium, and cesium. For sodium a related heterocubane derivative can also be obtained with a suitable phenolate ligand providing additional donor sites. One example is tetrameric [Na OC6H2-(CH2NMe2)2-2,6-Me-4 ]4, 172 [136], which contains tridentate pincer phenolate ligands and pentacoordinate sodium ions. 

Sodium trimethylsiloxide (trimethylsilanolate) is most conveniently made from the silanol or disiloxane using sodium. When prepared this way, it sublimes readily at 150°C and is soluble in organic solvents. The siloxides of the heavier alkali metals are tetrameric and have a cubane-like structure. 

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