1,2-Disilanediyl Bis(triflate), F₃CSO₃-SiH₂SiH₂-O ₃SCF₃, as the Key Intermediate for a Facile Preparation of Open-Chain and Cyclic 1,1- and 1,2-Diaminodisilanes

Convenient high-yield syntheses for several open-chain and cyclic diaminodisilanes with fully hydrogenated Si-Si linkages are reported. The key intermediate for the preparation of the title compounds, 1,2-bis(((trifluoromethyl)-sulfonyl)oxy)disilane (1), reacts with 2 equiv of diethylamine to afford a mixture of the isomers Et₂NSiH₂SiH₂NEt₂ (2a) and (Et₂N)₂SiHSiH₃ (2a′). Isopropylamine and 1 give ⁱPr₂NSiH₂SiH₂NⁱPr ₂ (2b) exclusively. Treatment of 1 with 1 equiv of a primary alkylamine affords 2,3,5,6-tetrasilapiperazines [RNSiH₂SiH₂RNSiH₂SiH₂; R = ⁱPr (3a), ^tBu (3b), Bzl (3c)] comprising two SiH₂-SiH₂ linkages. 1,3-Bifunctional bis(isopropylamino)silanes [(ⁱPrNH)₂SiR₂; R = Me, Ph] were found to react with 1 to give trisilaimidazolidines [(ⁱPrN)SiR₂(ⁱPrN)SiH₂SiH ₂; R = Me (4a), Ph (4b)] again comprising the N-SiH₂-SiH₂-N unit. The crystal structures of N,N′-diisopropyl-2,2-diphenyl-2,4,5-trisilaimidazolidine (4b) and N,N′-di-tert-butyl-2,3,5,6-tetrasilapiperazine (3b) were determined in X-ray diffraction studies; the five-membered ring of 4b is nearly planar with all nitrogen atoms in a planar configuration. The six-membered ring of 3b has a twist conformation, but again with the two nitrogen atoms in a planar configuration. Surprisingly, the treatment of 1 with 1,4-bifunctional N,N′-dialkylethylenediamines [(RNHCH₂-)₂; R = ⁱPr, ^tBu] does not give the analogous six-membered-ring compounds but leads selectively to the isomeric five-membered heterocycles [(CH₂NR)₂SiHSiH₃; R = ⁱPr (5a), ^tBu (5b)], which are the products of a Si → Si hydrogen shift rearrangement.