No abstract

No abstract

The dimethyl group-14 element dihalides Me2EX2 (E = Si, Ge, Sn; X = C1 or Br) react with two equivalents of Li[C(P-Me2),(SiMe3)] to give the cis-hexacoordinated complexes Me2E[C(PMe2)2(SiMe3)]2 (E = Si: 2a, E = Ge: 2b, E = Sn: Lc), which were characterized spectroscopically and by means of X-ray structure determinations. Whereas 2a and 2b are isotypic and crystallize in the space group P2,/c, 2c crystallizes in the space group C2/c with crystallographic C2(2) molecular symmetry. In all cases the diphosphanylmethanide ligands

The group-14 tetrahalides ECll (E = Si, Ge, Sn) react with two equivalents of Li [C(PMe&(SiMe,)] to give the trans-hexacoordinated complexes ClzE[C(PMe2)z(SiMe3)]2, which were characterized spectroscopically and by structure determinations in the solid state. The complexes were found to crystallize with or without tetrahydrofuran (THF) molecules, depending on the presence or absence of this solvent. In the case of the silicon complex, the structures of both crystal forms were determined, showing slightly different molecular structures of the complexes in the solid state. Without cocrystahzed THF, C1zSi[C(PMe2)2(SiMe3)]z has no crystallogra-phically imposed molecular symmetry, while in the presence of THF its crystallographic symmetry is C,, (2/m). The tin and germanium complexes were crystallized either with and without THF molecules, respectively, their crystal structures being isotypic with the respective ones of the silicon camplex. In all cases, small amounts of the cis-hexacoordinated isomers were also observed in solution, but only in the case of the silicon complex, it was isolated in pure form. It rearranges to the trans isomer at ambient temperature. trans-Cl,Si[ C (PMe2) &, trans-Cl,Si[ C(PPh&(SiMe3) l2 and cis-Me2-Si[ C(PMe&(SiMe3)lZ were likewise obtained.

Formation of partially fluorinated imidazoles 6 from 4,4-bis(trifluoromethyl)-1,3-diazabuta-1,3-dienes 1 in the presence of low-valent metal compounds is shown to proceed via a [4+1] cycloadduct in the case of germanium(II)-chloride. The resulting germole 3 has been characterized by X-ray analysis. The five-membered ring is planar and the germanium atom adopts tetrahedral configuration.