Novel Sila-Phospha-Heterocycles and Hypervalent Silicon Compounds with Phosphorus Donors

The reaction of two equivalents of lithium phosphinomethanides with di- or trifunctional chlorosilanes yields novel five- and six-membered heterocycles by multistep rearrangements or transmetallation reactions. Silaethene intermediates and hypervalent intermediates are likely to be involved. The reaction of one or two equivalents of lithium phosphinomethanide {Li[C(PMe2)2(SiMe2Ph)]}-TMEDA with pTolSiCl3 and °CH2CH2CH2SiCl2 yields novel penta- and hexacoordinated silicon complexes. Both are the first examples of truly hypervalent organosilicon species with phosphorus donors characterized by X-ray structure determination.