Small Cyclosilanes: Syntheses and Reactions toward Mono- and Dianions

The reaction of hexakis(trimethylsilyl)disilane with 2 equiv of potassium tert -butyl alcoholate and 18-crown-6 gives 1,2-dipotassiotetrakis(trimethylsilyl)disilane ( 1 ) in almost quantitative yield. Transmetalation with magnesium bromide allows for the derivatization of the dianion. After exchange of one or two trimethylsilyl groups for phenyl substituents in the starting material, the 1,2-dipotassio compounds ( 13, 16 ) could still be obtained. Treatment of 1 with 1,2-dibromoethane gives octakis(trimethylsilyl)cyclotetrasilane ( 8 ), which also can be converted into a 1,3-dipotassiocyclotetrasilane ( 11 ).