Synthesis and structure of fluorophenyl derivatives of the 10-vertex monocarbaborane anions [1-CB9H10]− and [2-CB9H10]−

Reactions of decaborane nido-B10H14 with a series of fluorobenzaldehydes in alkaline solution followed by treatment with iodine give the closo-[2-(X-FC6H4)-2-CB9H9]− anions (X = 2, 3, 4). Upon heating, these compounds rearrange to more thermodynamically stable closo-[1-(X-FC6H4)-1-CB9H9]− anions (X = 2, 3, 4). The compounds synthesized were characterized by multinuclear NMR spectroscopy. The crystal structures of (Bu4N)[1-(2-FC6H4)-1-CB9H9] and (Bu4N)2[2-(4-FC6H4)-2-CB9H9][1-(4-FC6H4)-1-CB9H9] were determined by single crystal X-ray diffraction.