Binary Si/N-[4.4]-Spirocycles with Two SiH(2)SiH(2) Loops.

Abstract

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 complementary analytical and spectroscopic data. The reaction of 1a-c with 2 equiv of Tf-SiH(2)SiH(2)-Tf (Tf = trifluoromethylsulfonyloxy, "triflate") and triethylamine in toluene gives good yields of the spirocyclic compounds [(SiH(2)NR)(2)](2)Si (2a-c). 2a is obtained as a crystalline, but highly volatile, product (mp 35 degrees C, bp(0.05) 46-47 degrees C), the crystal and molecular structure of which has been determined by single-crystal X-ray diffraction methods (monoclinic, space group P2(1)/n, Z = 8). The lattice contains two independent molecules in the asymmetric unit, which have very similar dimensions. The two five-membered rings are almost planar and close to perpendicular to each other. Owing to sterical hindrance, the analogous reaction of 1d gives only low yields of the corresponding spirocycle {[SiH(2)N(i-Pr)](2)}(2)Si, 2d. A silylammonium salt {[SiH(2)N(i-Pr)](2)Si-[NH(i-Pr)]-[NH(2)(i-Pr)]}(+)Tf(-) (3) is produced as a major product. Compound 3 is one of the very few silylammonium salts as confirmed by a full structural analysis (monoclinic, space group P2(1)/c, Z = 4). In the crystal, 2 equiv are grouped 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 1d and the 1,2-disilanediylbis(triflate) in the presence of NEt(3) give good yields of the monocyclic compound [SiH(2)N(i-Pr)](2)Si[NH(i-Pr)](2), 4. Compounds 1a-d and 2a-c are hydrogen- and silicon-rich precursor molecules for the production of silicon nitride in pyrolytic, plasma- or laser-induced (thermal) decomposition and for the preparation of silazane networks and gels by controlled aminolysis or by metathesis of the Si-Si bonds.