Icosahedral carboranes. XIII. Halogenation of p-carborane

Synthesis of Highly Iodinated Icosahedral Mono- and Dicarbon Carboranes

“…Indeed, it has been reported that a maximum of three bromine atoms can be substituted onto o -carbaborane, 3 , using AlCl 3 catalyst unless the carbons have an electron-donating alkyl substituent (e.g., methyl group) that increases the amount of substitution by 1 to a maximum of 4 bromine atoms . With m -dicarbaborane, 4 , and p -dicarbaborane, 5 , only the mono- and dibromo or diiodo derivatives could be obtained under the reaction conditions studied. 11b, In contrast to the closo -dicarbaboranes, it has been reported that closo -carbaboranes (monocarbon carboranes, e.g., 2 ) do not readily perhalogenate even with chlorine. Indeed, in an early study it was reported that reaction of the unsubstituted anionic monocarbon carborane with chlorine gas at 0 °C caused extensive degradation of the carborane molecule …”

“…Periodination of the borane cage molecules B 10 H 10 2- and B 12 H 12 2- , 1 , and a few of their substituted derivatives have been previously reported. 7a, Halogenation of cage boron atoms in closo -dicarbaboranes 3 − 5 has also been studied previously. While perfluorination and perchlorination of dicarbaboranes have been obtained, perhalogenation with bromine or iodine has not been accomplished. Indeed, it has been reported that a maximum of three bromine atoms can be substituted onto o -carbaborane, 3 , using AlCl 3 catalyst unless the carbons have an electron-donating alkyl substituent (e.g., methyl group) that increases the amount of substitution by 1 to a maximum of 4 bromine atoms .…”

Deuterium exchange at terminal boron-hydrogen bonds catalyzed by certain transition metal complexes. A qualitative study of selectivity and mechanism

“…Decaborane( 14), 1 ,2-C2BiqH 12, and 1.7-C2BioH|2 were sublimed prior to use. 1,12-C2BioHi242 was purified by chromatography with 30-60 °C petroleum ether on basic alumina according to the suggestion of Sieckhaus et al 43 Analysis by GLC showed the recrystallized product to contain less than 0.01% 1. Deuterium gas (99.7%) was obtained from Liquid Carbonic and was used as received for the early work described herein.…”

Four Decades of Organic Chemistry of closo-Boranes: A Synthetic Toolbox for Constructing Liquid Crystal Materials. A Review

“…The para isomer 6 (ref. 41 ) can be separated chromatographically 42 , taking advantage of the difference in the polarity 43 44 . This latter method is particularly convenient for large-scale preparations of 6.…”