Synthesis Of Mono- And Dihalogenated Derivatives Of (Me2s)(2)B12h10 And Palladium-Catalyzed Boron-Carbon Cross-Coupling Reactions Of The Iodides With Grignard Reagents

Two series of compounds, 9-X-1,7-(Me2S)(2)B12H9 and 9,10-X-2-1,7-(Me2S)(2)B12H8 (X = Cl, Br, l), have been synthesized from reactions of 1,7-(Me2S)(2)B12H10 with various halogenating reagents. In addition, reactions of 1,7-(Me2S)(2)B12H10 with 2,4-(NO2)(2)C6H3SCl and PhSeBr resulted in 9-(2',4'-(NO2)(2)C6H3S)-1,7-(Me2S)(2)B12H9 and 9,10-(PhSe)(2)-1,7(Me2S)(2)B12H8, respectively. X-ray studies of the dibromo, monoiodo, and aryl thioether derivatives show that electrophilic substitution in 1,7-(Me2S)(2)B12H10 takes place at positions 9 and 10, as in the case of the metacarborane 1,7-C2B10H12. From 1,12-(Me2S)(2)B12H10 the halides 2-X-1,12-(Me2S)(2)B12H9 (X = Br, l) were prepared. For both 1,7- and 1, 1 2-(Me2S)(2)B12H10 the best iodination results were obtained using iodine monochloride in refluxing acetonitrile. In the presence of 5 mol % (PPh3)(2)PdC12 the iodides 9-I-1,7-(Me2S)(2)B12H9, 2-I-1,12-(Me2S)(2)B12H9, and 9,10-I-2-1,7-(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 Cul as a cocatalyst. The bromo derivative 9-Br-1,7(Me2S)(2)B12H9 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)(2)B12H9. 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-Bn-2-1,7(Me2S)(2)B12H8 was significantly lower than those of the dimethyl and diphenyl derivatives. The molecular structures of 9-R-1,7-(Me2S)(2)B12H9 (R = Ph, Bn) and 2-Bn-1, 12-(Me2S)(2)B12H9 were obtained by single-crystal X-ray analysis.