Self-assembly of a Si-based cage by the formation of 24 equivalent covalent bonds.

A robust, nano-sized covalent cage, of composition, [(PhSi)6 (ctc)4 ]6- (H6 ctc = cyclotricatechylene) has been prepared in a simple reaction in good yield. The tetrahedral anionic cage is stable in both the solid and solution state and exhibits an affinity for Cs+ ions which bind to the internal surface of the cage.