PENTACOORDINATE AND HEXACOORDINATE SILICON-COMPOUNDS WITH PHOSPHORUS DONORS

The reaction of one or two equivalents of lithium phosphinomethanide { Li[C(PMe(2))(2)(SiMe(2)Ph)]} . TMEDA with p-TolSiCl(3) or CH2CH2CH2SiC l2 yields novel penta- and hexacoordinate silicon complexes. Both are the first examples of truly hypervalent organosilicon species with pho sphorus donors to be characterized by X-ray diffraction studies. The c rystal p-TolSiCl(2)[(PMe(2))(2)C(SiMe(2)Ph)] (1) adopts an intermediat e state between a trigonal bipyramid and a tetragonal pyramid. Compoun d CH2CH2CH2Si[(PMe(2))(2)C(SiMe(2)Ph)](2) (2) is cis-hexacoordinated i n solution and in the solid state, with comparable Si-P-ax and Si-P-eq bond lengths.