Synthesis of Mono- and Dihalogenated Derivatives of (Me2S)2B12H10 and Palladium-Catalyzed Boron-Carbon Cross-Coupling Reactions of the Iodides with Grignard Reagents

Two series of compounds, 9-X-1,7-(Me2S)2Bi2H9 and 9,1 O-1,7028)23128 (X = Cl, Br, 1), have been synthesized from reactions of 1,7-(Me2S)2B12Hio with various halogenating reagents. In addition, reactions of 1,7028)2812110 with 2,4-(NC)2)2C6H38CI and Ph8eBr resulted in 9-(2ʹ,4ʹ-(N02)2C6H38)-1,7-(Me28)2B12H9 and 9,10-(Ph8e)2-1,7(Me28)2Bi2H8, respectively. X-ray studies of the dibromo, monoiodo, and aryl thioether derivatives show that electrophilic substitution in 1,7-(Me28)2B12Hio takes place at positions 9 and 10, as in the case of the metacarborane IJBioH. From 1,12-(Me28)2B12Hio the halides 2-X-1,12-(Me28)2Bi2H9 (X = Br, 1) were prepared. For both 1,7- and 1,12-(Me28)2B12Hio the best iodination results were obtained using iodine monochloride in refluxing acetonitrile. In the presence of 5 mol % (PPh3)2PdCl2 the iodides 9-1-1,7-(Me28)2Bi2H9, 2-1-1,12-(Me28)2Bi2H9, and 9,10-12-1,7-(Me28)2Bi2H8 react with RMgX (R = Me, Ph, Bn; X = Cl, Br) in THF to yield the corresponding B-alkyland B-aryl-substituted products in good yields without using Cul as a cocatalyst. The bromo derivative 9-Br-1,7(Me28)2Bi2Hg did not react under similar conditions. No interference from the nearby me2s substituent was observed in palladium-catalyzed substitution of iodide in 2-1-1,12-(Me28)2Bi2H9. 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(Me28)2B12H8 was significantly lower than those of the dimethyl and diphenyl derivatives. The molecular structures of 9-R-1,7-(Me28)2B12H9 (R = Ph, Bn) and 2-Bn-1,12-(Me28)2Bi2H9 were obtained by single-crystal X-ray analysis.