Notizen: Synthesis and Structure of a 2,4,5-Tris(methylene)-1-bora-3-silacyclopentane Derivative

Abstract

; the latter react with a second Fe(CO)3 group to yield slipped triple-decker com plexes ( 1) [Fe(CO)3]2 [3], Form al replacement of a boryl group B -R 1 in 1 with the SiMe2 moiety should lead to the l-bora-3-silafulvene heterocycle (2). Our attem pts to synthesize 2 were not success ful. However, a rearrangem ent of 4, analogous to that of the 2,4,5-tris(methylene)-l,3-diborolane (3) to yield 1 (R2 = C H (C H 3)2, R2 = C (C H 3) = C H 2) via a 1,5-hydrogen shift [4], may provide a route to 2. Here we report the synthesis and structure of the title com pound 4. ResultsSeveral unsaturated [5,6 ] and saturated [7] het erocyclic compounds with non-adjacent boron-silicon atoms are known. Recently, we described the unexpected formation o f a l,3-dibora-2,5-disilacyclohexane derivative by reacting com pound 5 with N a/K alloy [8]. 5 was obtained via hydroboration of Me3C -C = C -S iM e 2Cl with HBCl2 OEt2 and subsequent substitution of one chlorine atom by a N M e2 group. Treatm ent of 5 with 3,4-dilithio-2,5-dimethyl-2,4-hexadiene [9] in diethylether leads to 4 in 41% yield. The product can be dis tilled in vacuo and recrystallized from pentane at -2 0 °C.