Synthesis and structural characterization of mono- and bisfunctional o-carboranes

Abstract

Functionalized o-carboranes are interesting ligands for transition metals. Reaction of LiC₂B₁₀H₁₁ with Me₂NCH₂CH₂Cl in toluene afforded 1-Me₂NCH₂CH₂-1,2-C₂B₁₀H₁₁ (1). Treatment of 1 with 1 equiv. of n-BuLi gave [(Me₂NCH₂CH₂)C₂B₁₀H₁₀]Li ([1]Li), which was a very useful synthon for the production of bisfunctional o-carboranes. Reaction of [1]Li with RCH₂CH₂Cl afforded 1-Me₂NCH₂CH₂-2-RCH₂CH₂-1,2-C₂B₁₀H₁₀ (R = Me₂N (2), MeO (3)). 1 and 2 were also prepared from the reaction of Li₂C₂B₁₀H₁₀ with excess Me₂NCH₂CH₂Cl. Treatment of [1]Li with excess MeI or allyl bromide gave the ionic salts, [1-Me₃NCH₂CH₂-2-Me-1,2-C₂B₁₀H₁₀][I] (4) and [1-Me₂N(CH₂CHCH₂)CH₂CH₂-2-(CH₂CHCH₂)-1,2-C₂B₁₀H₁₀][Br] (6), respectively. Interaction of [1]Li with 1 equiv. of allyl bromide afforded 1-Me₂NCH₂CH₂-2-(CH₂CHCH₂)-1,2-C₂B₁₀H₁₀ (5). Treatment of [1]Li with excess dimethylfulvene afforded 1-Me₂NCH₂CH₂-2-C₅H₅CMe₂-1,2-C₂B₁₀H₁₀ (7). Interaction of [1]Li with excess ethylene oxide afforded an unexpected product 1-HOCH₂CH₂-2-(CH₂CH)-1,2-C₂B₁₀H₁₀ (8). 1 and 3 were conveniently converted into the corresponding deborated compounds, 7-Me₂NHCH₂CH₂-7,8-C₂B₉H₁₁ (9) and 7-Me₂NHCH₂CH₂-8-MeOCH₂CH₂-7,8-C₂B₉H₁₀ (10), respectively, in MeOH–MeOK solution. All of these compounds were characterized by various spectroscopic techniques and elemental analyses. The solid-state structures of 4 and 6–10 were confirmed by single-crystal X-ray analyses.