Syntheses and Reactivity of Stannyloligosilanes. 2.† Branched Stannyloligosilanes

Branched tri(stannyl)tetrasilanes MeSi[SiMe2SnR2R‘]3 (2, R = R‘ = Ph; 3, R = R‘ = Me; 5, R = t-Bu, R‘ = H) were synthesized by the reaction of alkali metal tri- or diorganostannides with methyltris(fluorodimethylsilyl)silane (1) or methyltris(chlorodimethylsilyl)silane (4) or by reacting triphenylchlorostannane with 1 in the presence of magnesium. Methyltris[(hydridodi-tert-butylstannyl)dimethylsilyl]silane (5) was halogenated at the tin atom by treatment with CHCl3 or CHBr3. Surprisingly, the reaction of 5 with 3 equiv of lithium diisopropylamide (LDA) resulted in the formation of the five-membered ring 10 (2-dimethylsilyl-1,1,2,3,3-pentamethyl-4,4,5,5-tetra-tert-butyl-1,2,3-trisila-4,5-distannacyclopentane) with a bridging Sn−Sn unit. Reacting 5 with triethylamine or aminostannanes resulted in the formation of 2-dimethylsilyl-1,1,2,3,3-pentamethyl-4,4,5,6,6-penta-tert-butyl-1,2,3-trisila-4,5,6-tristannacyclohexane (14). The solid-state structures of 5 and 14b were determined by X-ray crystallography.