Synthesis and Structures of Extended Cyclic Siloxanes.

ABSTRACT The facile synthesis of all- cis-tetrasiloxycyclotetrasiloxanes (extended cyclic siloxanes) [ i-BuSi(OSiHMe2)O]4 1, [PhSi(OSiHMe2)O]4 2, and [CH2 = CHSi(OSiHMe2)O]4 3 was accomplished via sodium or potassium silanolates from respective trialkoxysilanes. The treatment of 1 or 2 with m-chloroperoxybenzoic acid afforded respective extended cyclic silanols [ i-BuSi(OSiMe2OH)O]4 4 and [PhSi(OSiMe2OH)O]4 5. The structures of 4 and 5 were unequivocally established by X-ray crystallography. Among these new compounds, compound 3 possesses both vinyl and hydrosilyl groups in the molecule, thus this could serve as a potential monomer of well-defined cage silsesquioxanes. Extended cyclic silanols 4 and 5 contain four silanol moieties in the same direction, and application of host molecules or building units of cage silsesquioxanes is expected. [ABSTRACT FROM AUTHOR]