Article abstract of DOI:10.1016/0022-328X(95)05967-T

Sterically overloaded digermylsilylmethanes ^tBu₂SiX-CY(GeMe₃)₂ (X = H, Me, F, Br; Y = H, Br, Li) 7-16 are accessible via ^tBu₂SiH-CH(GeMe₃)₂ 7 (from ^tBu₂SiHF and LiCH(GeMe₃)₂). The compounds are distinguished by hindered rotation about the SiC single bond shown. 7-16 enter into many reactions: (i) electrophilic substitution of Y = H by Li started with MeLi/THF, or of Y = Li by Br, EMe₃, R started with Br₂, Me₃SnCl, Me₃GeCl, Me₃SiO(CH₂)₄Cl, or of X - H by Br started with Br₂; (ii) homophilic substitution of Y = Br by H started with ^tBu₃SiNa; (iii) nucleophilic substitution of X = F, Br by R started with MeLi, ⁿBuLi. The latter reactions are possible only when Y = Li, and probably proceed over the silaethen ^tBu₂Si=C(GeMe₃)₂ as reaction intermediate. ^tBu₂SiF-CLi(GeMe₃)₂, a potential precursor of the hitherto unknown germaethene Me₂Ge=C(GeMe₃)(SiMe^tBu₂), forms an adduct Li(THF)⁺₄ [^tBu₂SiF-C(GeMe₃)₂] in THF and an adduct ^tBu₂SiF-CLi(GeMe₃)₂·2THF after evaporation of THF. The structure of the latter compound shows a distorted tetrahedral geometry of the central Si and C atom with the Li atom being bonded to the latter. In addition, Li is coordinated by two molecules of THF in a slightly distorted trigonal-planar geometry. A short F ··· Li contact is not observed. (Crystals of ^tBu₂SiF-CLi(GeMe₃)₂·2THF are orthorhombic, space group Pca2₁, with a = 20.739(3), b = 16.185(5), c = 17.642(4) A, V = 5921.4 A³, Z= 8, D_calc = 1.256 g cm^-3. R = 0.057 for 527 refined parameters and 4144 observed data.) ^tBu₂SiF-CLi(GeMe₃)₂·TMEDA is supposed to have a similar structure. ^tBu₂SiH-CLi(GeMe₃)₂·OP(NMe₂)₃ and ^tBu₂SiMe-CLi(GeMe₃)₂·OEt₂ have different strutures.