Article abstract of DOI:10.1016/S0022-328X(96)06687-9

Sterically overloaded trisilylmethanes R*(Me₃Si)(Me₂XSi)CY = Me₂SiX-CYR*(SiMe₃) (X = H, Br, F, OH, OMe, OC₆F₅, OTf, Me, ⁿBu, Ph; Y = H, Br, Me) with R* = supersilyl Si^tBu₃ are accessible via Me₂SiH-CHR*(SiMe₃) (from Me₂SiHCl and LiCHR*(SiMe₃)). The latter compound reacts (i) with Br₂ to Me₂SiBr-CHR*(SiMe₃) which is transformed with AgF, H₂O, MeOH, C₆F₅OLi, MeLi, ⁿBuLi, PhLi into Me₂SiX-CHR*(SiMe₃) (X = F, OH, OMe, OC₆F₅, Me, ⁿBu, Ph), (ii) with MeLi and then Br₂ to Me₂SiBr-CBrR*(SiMe₃) which is transformed with KHF₂, H₂O, TfOH into Me₂SiX-CBrR*(SiMe₃) (X = F, OH, OTf). Compounds Me₂SiX-CHR*(SiMe₃) (X = F, OC₆F₅) react at room temperature with MeLi in THF mainly under H/Li and X/Me exchange. At -78°C, Me₂SiX-CHR*(SiMe₃) (X = OC₆F₅) is transformed by MeLi under exchange of a meta-or a para-fluorine of C₆F₅ by a Me group (X-ray structure analysis of the product with X = p-OC₆F₄Me). In contrast, reaction of Me₂SiX-CBrR*(SiMe₃) (X = F, OTf) with PhLi or with ⁿBuLi leads to Me₂SiR-CLiR*(SiMe₃) (R = Ph, ⁿBu), while Me₂SiF-CBrR*(SiMe₃) reacts with ^tBu₃SiNa to Me₂SiF-CNaR*(SiMe₃). The latter compound transforms in THF in the presence of Me₃SiCl into the silaethene Me₂Si=CR*(SiMe₃), which after evaporation of THF isomerizes into a 1,3-disilacyclobutane [-SiMe₂-CH₂-SiMe₂-CHR*-], while it may be trapped in THF solution by reactants like MeOH, Me₂CO, or CH₂ =CMe-CMe=CH₂. It follows from our studies that the metastability of compounds Me₂Si=C(SiMe₃)(SiMe_3-n ^tBu_n) with an increasing number of ^tBu groups pass through a maximum for n = 2.