REACTIONS OF STERICALLY HINDERED ORGANOZINC AND ORGANOCADMIUM COMPOUNDS CONTAINING FUNCTIONAL SILICON CENTERS - CRYSTAL-STRUCTURES OF ZN[C(SIME3)2(SIME2OCOCF3)]2 AND CD[C(SIME3)2(SIME2OME)]2

The compound (Me3Si)2CCl2 was converted by treatment with BuLi/Et2O/THF and then with Me2HSiCl into (Me3Si)2CCl(SiMe2H). Further lithiation with BuLi gave LiC(SiMe3)2(SiMe2H), which reacted with ZnBr2 to yield Zn[C(SiMe3)2(SiMe2H)]2. Thence, several new organozinc compounds Zn[C(SiMe3)2(SiMe2X)]2, with X = Cl, Br, I, F, OH, OMe, O2CCF3, O2CH, or NCS, were obtained by substitutions at silicon without cleavage of Zn-C bonds. The compounds Cd[C(SiMe3)2(SiMe2X)]2, with X = H, OMe, and Ph, were obtained similarly, but subsequent substitutions at Si were accompanied by reactions at Cd. The crystal structure of the trifluoroacetato derivative Zn[C(SiMe3)2(SiMe2 OCOCF3)]2 shows that the molecules are centrosymmetric, with the O2CCF3 groups forced outwards by steric hindrance away from the metal centre. In Cd[C(SiMe3)2(SiMe2OMe)]2, the methoxy groups are folded in towards cadmium but the Cd ... O distance is only slightly shorter than the sum of the van der Waals radii.