BINARY SI N-[4.4]-SPIROCYCLES WITH 2 SIH2SIH2 LOOPS/

Tetra(alkylamino)silanes Si(NHR)(4) with R = Me, n-Pr, n-Bu, and i-Pr (1a-d) have been prepared via improved methods and characterized by co mplementary analytical and spectroscopic data. The reaction of 1a-c wi th 2 equiv of Tf-SiH2SiH2-Tf (Tf = trifluoromethylsulfonyloxy, ''trifl ate'') and triethylamine in toluene gives good yields of the spirocycl ic compounds [(SiH2NR)(2)](2)Si (2a-c). 2a is obtained as a crystallin e, but highly volatile? product (mp 35 degrees C, bp(0.05) 46-47 degre es C), the crystal and molecular structure of which has been determine d by single-crystal X-ray diffraction methods (monoclinic, space group P2(l)/n, Z = 8). The lattice contains two independent molecules in th e asymmetric unit, which have very similar dimensions. The two five-me mbered rings are almost planar and close to perpendicular to each othe r. Owing to sterical hindrance, the analogous reaction of Id gives onl y low yields of the corresponding spirocycle ([SiH2N(i-Pr)](2))(2)Si, 2d. A silylammonium salt {[SiH2N(i-Pr)](2)Si-[NH(i-Pr)]-[NH2(i-Pr)]}Tf -+(-) (3) is produced as a major product. Compound 3 is one of the ver y few silylammonium salts as confirmed by a full structural analysis ( monoclinic, space group P2(l)/c, Z = 4). In the crystal, 2 equiv are g rouped together as a centrosymmetrical cluster of two cations and two anions with hydrogen bonds between the amino/ammonio and the sulfonate groups. Equimolar quantities of Id and the 1,2-disilanediylbis(trifla te) in the presence of NEt3 give good yields of the monocyclic compoun d [SiH2N(i-Pr)](2)-Si[NH(i-Pr)](2), 4. Compounds 1a-d and 2a-c are hyd rogen-and silicon-rich precursor molecules for the production of silic on nitride in pyrolytic, plasma-or laser-induced (thermal) decompositi on and for the preparation of silazane networks and gels by controlled aminolysis or by metathesis of the Si-Si bonds.