HEXACOORDINATED GROUP-14 ELEMENTS WITH PHOSPHORUS DONOR LIGANDS - SYNTHESES AND STRUCTURES OF CL(2)E[C(PME(2))(2)(SIME(3))](2) (E=SI,GE,SN)

The group-14 tetrahalides ECl(4) (E = Si, Ge, Sn) react with two equiv alents of Li[C(PMe(2))(2)(SiMe(3))] to give the trans-hexacoordinated complexes Cl(2)E[C(PMe(2))(2)(SiMe(3))](2), which were characterized s pectroscopically and by structure determinations in the solid state. T he 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 f orms were determined, showing slightly different molecular structures of the complexes in the solid state. Without cocrystallized THF, Cl2Si [C(PMe(2))(2)(SiMe(3))]2( )has no crystallographically imposed molecul ar symmetry, while in the presence of THF its crystallographic symmetr y is C-2h (2/m). The tin and germanium complexes were crystallized eit her with and without THF molecules, respectively, their crystal struct ures being isotypic with the respective ones of the silicon complex. I n all cases, small amounts of the cis-hexacoordinated isomers were als o observed in solution, but only in the case of the silicon complex, i t was isolated in pure form. It rearranges to the trans isomer at ambi ent temperature, trans-Cl2Si[C(PMe(2))(3)](3), trans-Cl2Si[C(PPh(2))(2 )(SiMe(3))](2) and cis-Me(2)Si[C(PMe(2))(2)(SiMe(3))](2) were likewise obtained.