Synthesis of Mono- and Dihalogenated Derivatives of (Me2S)2B12H10 and Palladium-Catalyzed Boron−Carbon Cross-Coupling Reactions of the Iodides with Grignard Reagents
- 12 April 2003
- journal article
- research article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 42 (10) , 3199-3207
- https://doi.org/10.1021/ic020600u
Abstract
Two series of compounds, 9-X-1,7-(Me2S)2B12H9 and 9,10-X2-1,7-(Me2S)2B12H8 (X = Cl, Br, I), have been synthesized from reactions of 1,7-(Me2S)2B12H10 with various halogenating reagents. In addition, reactions of 1,7-(Me2S)2B12H10 with 2,4-(NO2)2C6H3SCl and PhSeBr resulted in 9-(2‘,4‘-(NO2)2C6H3S)-1,7-(Me2S)2B12H9 and 9,10-(PhSe)2-1,7-(Me2S)2B12H8, respectively. X-ray studies of the dibromo, monoiodo, and aryl thioether derivatives show that electrophilic substitution in 1,7-(Me2S)2B12H10 takes place at positions 9 and 10, as in the case of the meta-carborane 1,7-C2B10H12. From 1,12-(Me2S)2B12H10 the halides 2-X-1,12-(Me2S)2B12H9 (X = Br, I) were prepared. For both 1,7- and 1,12-(Me2S)2B12H10 the best iodination results were obtained using iodine monochloride in refluxing acetonitrile. In the presence of 5 mol % (PPh3)2PdCl2 the iodides 9-I-1,7-(Me2S)2B12H9, 2-I-1,12-(Me2S)2B12H9, and 9,10-I2-1,7-(Me2S)2B12H8 react with RMgX (R = Me, Ph, Bn; X = Cl, Br) in THF to yield the corresponding B-alkyl- and B-aryl-substituted products in good yields without using CuI as a cocatalyst. The bromo derivative 9-Br-1,7-(Me2S)2B12H9 did not react under similar conditions. No interference from the nearby Me2S substituent was observed in palladium-catalyzed substitution of iodide in 2-I-1,12-(Me2S)2B12H9. Presumably due to the intramolecular activation of an aryl C−H bond of the benzyl substituent in the inermediate palladium complex, the yield of 9,10-Bn2-1,7-(Me2S)2B12H8 was significantly lower than those of the dimethyl and diphenyl derivatives. The molecular structures of 9-R-1,7-(Me2S)2B12H9 (R = Ph, Bn) and 2-Bn-1,12-(Me2S)2B12H9 were obtained by single-crystal X-ray analysis.Keywords
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