SYNTHESIS OF SILYLATED DERIVATIVES OF THE CUBIC OCTAMERIC SILICATE SPECIES SI8O20(8-)

Silylated derivatives of the double eight-membered ring (Si4O4) silicate species (Si8O208-) have been synthesized by the reaction of Si8O208-, present dominantly in a methanolic solution of tetramethylammonium silicate, with organodimethylchlorosilanes [R(CH3)2SiCl, R = CH3, CH = CH2, CH2Cl, C6H5]. The effects of tetrahydrofuran (THF) and 2,2-dimethoxypropane (DMOP) as a solvent for the reaction have been investigated. When THF has been used as a solvent, incompletely silylated derivatives of Si8O208- with silanol groups, Si8O20[Si(CH3)2R]8-n(H)n (n = 1-3), have been formed together with the completely silylated derivative, Si8O20[Si(CH3)2R]8. On the other hand, formation of the incompletely silylated derivatives has been suppressed and a yield of the completely silylated derivative has increased by using DMOP as a solvent, indicating that DMOP is an efficacious solvent for the synthesis of Si8O20[Si(CH3)2R]8 from Si8O208- and R(CH3)2SiCl.