Deboronation of C-substituted ortho- and meta-closo-carboranes using “wet” fluoride ion solutions

Abstract

Hydrated tetrabutylammonium fluoride has been found to be more effective than the anhydrous salt as a reagent for the conversion of ortho and metal closo-carborane derivatives, R′R″C 2B 10H 10, into nido-carborane anions, [R′R″C 2B 9H 10] −, allowing access to a number of new nido-carborane derivatives difficult to prepare, or inaccessible, using other deboronating reagents, notably the meta-carborane derivatives, [7,9-R′R″-7,9-C 2B 9H 10] − [Bu 4N] + (R′ = 4-HOC 6H 4, 4-O 2NC 6H 4; R″ = H and R′ = R″ = 4-PhOC 6H 4, 4-O 2NC 6H 4, 2-C 5H 4N, 4-H 2NC 6H 4). Experiments with the bis( p-bromophenyl- ortho-carboranyl)benzene, 1,4-[4-BrC 6H 4CB 10H 10C] 2C 6H 4, carried out to determine the quantity of tetrabutylammonium fluoride needed to deboronate both cages, afforded the salt 1,4-[7-(4-BrC 6H 4)C 2B 9H 10] 2C 6H 4 2−[Bu 4N +] 2