SYNTHESIS AND STRUCTURE OF A MANXANE-CAGE SILAZANE MOLECULE

The reaction of tris(chlorodimethylsilyl)methane HC(SiMe2Cl)3 (1) with dry ammonia in hexane leads to the tris(disilazane) molecule HC(Me2Si NHSiMe2)3CH (3) in satisfactory yields. According to its H-1, C-13, an d Si-29 NMR spectra this bicyclic cage-molecule exhibits virtual (time -averaged) D3h symmetry. In the crystal (rhombohedral, space group R3B AR) the manxane-type structure has a crystallographic three-fold axis, but the structure obeys only D3d symmetry to a good approximation, ow ing to a disrotatory twist of the two Si3 triangles against each other . The crystals of compound 3 are isomorphous with those of the analogo us tris(disiloxane) 2.