Development and Application of New Steric Protection Group for Stabilization of Highly Reactive Organic Species

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In recent years much attention has been paid to a new methodology for isolation of highly reactive chemical species which takes advantage of kinetic stabilization by sterically bulky groups. In the present study new bulky groups for stecric protection , i. e., benzene derivatives bearing (Me_3Si)_3C, (Me_3Si)_2CH, (Me_3Si)_2CMe at their o-positions, have been developed and various new compounds having this group have been prepared. Among them, 2, 4, 6-tris[bis (trimethylsilyl) methyl] phenyl group (Tb group) is especially useful baeuse it can be easily synthesized from mesitylene by chlorination and subsequent trimethylsilation and found to be bulkier than often used 2, 4, 6-tri-t-butylphenyl group. TbLi, obtained through bromination of TbH followedd by lithiation with t-BuLi, were converted into very sterically bulky compounds Tb (Mes) MX_2 (Mes = mesityl ; M=Si, Ge, Sn ; X=CL, H). New polysulfides and polyselenides Tb (Mes) MS_4 (Y=S or Se) were obtained from Tb (Mes) MX_2 and their structures were establised by X-ray structural analysis. These compounds are considered to be excellent precursors of compounds having M=Y bonds (M=Si, Ge, Sn : Y=S, Se) and indeed Tb (Mes) MS_4 (M=Ge, Sn) readily reacted with hexamethyl phosphorous triamide to give products which were considered to be formed via germanethione (Ge=S) and stannanethione (Sn=S). The polyselenides Tb (Mes) MSe_4 behaved similarly.