1,2-Disilanediyl Bis(triflate), F(3)CSO(3)-SiH(2)SiH(2)-O(3)SCF(3), 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 Et(2)NSiH(2)SiH(2)NEt(2) (2a) and (Et(2)N)(2)SiHSiH(3) (2a'). Isopropylamine and 1 give (i)Pr(2)NSiH(2)SiH(2)N(i)Pr(2) (2b) exclusively. Treatment of 1 with 1 equiv of a primary alkylamine affords 2,3,5,6-tetrasilapiperazines [RNSiH(2)SiH(2)RNSiH(2)SiH(2); R = (i)Pr (3a), (t)Bu (3b), Bzl (3c)] comprising two SiH(2)-SiH(2) linkages. 1,3-Bifunctional bis(isopropylamino)silanes [((i)PrNH)(2)SiR(2); R = Me, Ph] were found to react with 1 to give trisilaimidazolidines [((i)PrN)SiR(2)((i)PrN)SiH(2)SiH(2); R = Me (4a), Ph (4b)] again comprising the N-SiH(2)-SiH(2)-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 [(RNHCH(2)-)(2); R = (i)Pr, (t)Bu] does not give the analogous six-membered-ring compounds but leads selectively to the isomeric five-membered heterocycles [(CH(2)NR)(2)SiHSiH(3); R = (i)Pr (5a), (t)Bu (5b)], which are the products of a Si --> Si hydrogen shift rearrangement.