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

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.