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).