achieved with LiNHR′ which allows the synthesis of mixed bisaminosilanes (R′HN)(R″HN)SiPh2. The X-ray structures of three of these compounds have been determined. There are no intermolecular N-H···N hydrogen bonds in these compounds in the solid state. Several 1,3,2,4-diazaphosphetidines have been synthesized using bis(N-lithioamino)silanes and bis(N-lithioamino)phosphanes . Amongst these the heterocycle