Hypersilyl group

The hypersilyl group allows isolation of stable gallium silyl compounds with tri- and tetracoordinated gallium centres. The GaSi bond seems to be inert to protic reagents. 

Methoxy-bis[tris(trimethylsilyl)silyl]methane (4) - the first compound bearing two hypersilyl groups at a carbon atom - was synthesized by the reaction of tris(trimethylsilyl)silyllithium (1) with dichloromethyl methyl ether in a yield of 35 % In view of the extreme bulkiness of the two hypersilyl substituents, the ease of the formation of 4 is really surprising. But the reaction pathway is easily understood as a consecutive replacement of the two chlorine atoms of the dichloromethyl methyl ether by the silanide 1 (Eq. 1). 

Keywords Hypersilyl / Group 15 Cages / Cyclotrisilane / Crystal Structure... 

The synthesis of tris(trimethylsilyl)silylphosphine (Scheme 2) yielded colorless crystals that could easily be purified by vacuum sublimation. Contrary to the observations made by Uhlig [3] with the Si(CH3)3 substituent, we were not able to introduce more than one bulky hypersilyl group to PHj. 

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