Halogen derivatives of monocarbon carboranes, nido-7-Me3N-7-CB10H12, closo-2-Me3N-2-CB10H10 and closo-1-Me3N-1-CB11H11‡

Abstract

Electrophilic iodination and bromination (X₂–AlCl₃) of nido-7-Me₃N-7-CB₁₀H₁₂ gave nido-4-I-7-Me₃N-7-CB₁₀H₁₁ and nido-4,6-I₂-7-Me₃N-7-CB₁₀H₁₀ and the bromine-substituted analogues nido-4-Br-7-Me₃N-7-CB₁₀H₁₁ and nido-4,6-Br₂-7-Me₃N-7-CB₁₀H₁₀. Electrophilically induced nucleophilic substitution (HI–AlCl₃) gave nido-9-I-7-Me₃N-7-CB₁₀H₁₀. These compounds readily deprotonated to the dianions [nido-7-Me₃N-7-CB₁₀H₁₀]^2–, [nido-4-I-7-Me₃N-7-CB₁₀H₉]^2– and [nido-4,6-I₂-7-Me₃N-7-CB₁₀H₈]^2–, and oxidation (chemical or electrochemical) gave derivatives of closo-2-Me₃N-2-CB₁₀H₁₀ and closo-3-I-2-Me₃N-2-CB₁₀H₉. Low temperature insertion reactions of the anions with PhBCl₂ gave closo-8-I-2-Ph-1-Me₃N-1-CB₁₁H₉ and closo-8-Br-2-Ph-1-Me₃N-1-CB₁₁H₉, while electrophilic iodination occurred at B(12) to give closo-12-I-1-Me₃N-1-CB₁₁H₁₀. Palladium catalysed substitution of iodine resulted in the nido and closo derivatives closo-8-CH₂CHCH₂-2-Ph-1-Me₃N-1-CB₁₁H₉ and nido-4-CH₂CHCH₂-7-Me₃N-7-CB₁₀H₁₁. AM1 Calculations were used to help rationalise a mechanism for the boron insertion reactions.