Auf dem wege zu einem stabilen germaethen Ge = C<1: Sterisch überladene digermylsilylmethane tBu2SiXCY(GeMe3)2 und struktur der germaethenquelle tBu2SiFCLi(GeMe3)2 · 2THF
作者:Nils Wiberg、Hae-Sook Hwang-Park、Patrizia Mikulcik、Gerhard Müller
DOI:10.1016/0022-328x(95)05967-t
日期:1996.4
Sterically overloaded digermylsilylmethanes (t)Bu(2)SiX-CY(GeMe(3))(2) (X - H, Me, F, Br, Y = H, Br, Li) 7-16 are accessible via (t)Bu(2)SiH-CH(GeMe(3))(2) 7 (from (1)Bu(2)SiHF and LiCH(GeMe(3))(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/TH, or of Y = Li by Br, EMe(3), R started with Br-2, Me(3)SnCl, Me(3)GeCl, Me(3)SiO(CH2)(4)Cl, or of X = H by Br started with Br-2; (ii) homophilic substitution of Y = Br by H started with (t)Bu(3)SiNa; (iii) nucleophilic substitution of X = F, Br by R started with MeLi, (II)BuLi. The latter reactions are possible only when Y = Li, and probably proceed over the silaethen t(B)u(2)Si=C(GeMe(3))(2) as reaction intermediate. (t)Bu(2)SiF-CLi(GeMe(3))2, a potential precursor of the hitherto unknown germaethene Me(2)Ge=C(GeMe(3))(SiMe(t)Bu(2)), forms an adduct Li(THF)(4)(+) [(t)Bu(2)SiFC(GeMe(3))(2)](-) in THF and an adduct (t)Bu(2)SiF-CLi(GeMe(3))(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 (t)Bu(2)SiF-CLi(GeMe(3))(2) . 2THF are orthorhombic, space group Pca2(1), with a = 20.739(3), b = 16.185(5), c = 17.642(4) Angstrom, V = 5921.4 Angstrom(3), Z = 8, D-calc = 1.256 g cm(-3). R = 0.057 for 527 refined parameters and 4144 observed data.) (t)Bu(2)SiF-CLi(GeMe(3))(2) . TMEDA is supposed to have a similar structure. (t)Bu(2)SiH-CLi(GeMe(3))(2) . OP(NMe(2))(3) and (t)Bu(2)SiMe-CLi(GeMe(3))(2) . OEt(2) have different structures.