Syntheses and reactivity of stannyloligosilanes. III. Lithiated stannasilanes - Building blocks for monocyclic Si-Sn rings

Dilithiated di(stannyl)oligosilanes ((Bu2Sn)-Bu-t(Li)-(SiMe2)(n)-Sn(Li)Bu-t (2); 4, n = 2; 5, n = 3) were synthesized by the reaction of lithium diisop ropylamide (LDA) with the alpha,omega -hydrido tin substituted oligosilanes ((Bu2Sn)-Bu-t(H)-(SiMe2)(n)-Sn(H)Bu-t(2); 1, n = 2; 2, n = 3). Surprisingl y, the reaction of 1 and 3 ((Bu2Sn)-Bu-t(H)-(SiMe2)(4)-Sn(H)Bu-t(2)) with L DA resulted not in the formation of the lithiated compound, but what one ca n find is the formation of the 5,5-ditert.butyl-octamethyl-1,2,3,4-tetrasil a-5-stannacyclopentane (8) (n = 4) in addition to the expected product 4 (n = 4) and the 3,3,6,6-tetratert.butyl-octamethyl-1,2,4,5-tetrasila-3,6-dist an-nacyclohexane (7) (n = 3). Reactions of 4 and 5 with dimethyl and diphenyldichlorosilanes yielding mon ocyclic Si-Sn derivatives (9-11) are also discussed. The solid-state struct ures of 7 and 11 were determined by X-ray crystallography.