Synthesis and structural characterization of highly chlorinated, brominated, iodinated, and methylated carborane anions, 1-H-CB9X9-, 1-NH2-CB9X9- (X = Cl, Br, I), and 1-H-CB9(CH3)9-

The highly chlorinated, brominated, and iodinated carborane anions 1-R-CB9X9- (R = H, NH2; X = Cl, Br, I) were prepared in high yields by treatment of [Me3NH][1-R-CB9H9] with excess ICI, Br-2/triflic acid, and I-2/triflicacid, respectively, in sealed tubes at 180-240 degrees C. With the aid of a Pd catalyst, B-I bonds could be converted into the B-Me bonds by treatment with excess MeMgBr, which led to the preparation of the permethylated species 1-H-CB9Me9- in good yield. These new anions were fully characterized by H-1, C-13, and B-11 NMR, IR, and negative-ion MALDI MS spectroscopy. Some were further characterized by single-crystal X-ray analyses. The weakly coordinating nature of these new anions was probed by Si-29 chemical shifts.