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The metallo−carbohedrene V8C12 + is studied using a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled to a compact supersonic source. Its reactions with water, ammonia, ROH (R = CH3, C2H5, C3H7, C4H9), and CH3X (X = Cl, Br, I) are reported. For polar molecules, sequential attachment reactions occur leading to the initial buildup of the product V8C12L4 +. V8C12L5-7 + peaks for ammonia and alcohols are also observed, but they grow in slowly. These results provide evidence that the geometric structure of V8C12 + is the theoretically calculated more stable T d or D 2 d symmetry with two sets of metals, as opposed to the T h symmetry with all eight equivalent metals. In reactions with methyl halide, CH3X (X = Cl, Br, I), V8C12 + undergoes four sequential halide abstraction reactions, exclusively, yielding mass spectra that truncate sharply at V8C12X4 +. Dehydrogenation is observed for the secondary reactions with water and alcohols, ROH (R = H, alkyl), yielding V8C12(OR)2 + intermediates. The results from this study are compared to those of other met-cars.

A compact supersonic source is employed with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer to generate and investigate the metallocarbohedrene, Nb 8 C 12 + . Nb 8 C 12 + reacts with water and alcohols via sequential attachments and dehydrogenations leading to the initial truncation products Nb 8 C 12 -(OR) 4 + (R ) H, CH 3 , C 2 H 5 , C 4 H 9 ). Also, Nb 8 C 12 + reacts with NH 3 via sequential attachments to produce the initial truncation product Nb 8 C 12 (NH 3 ) 4 + . Nb 8 C 12 L 5-8 + peaks for ammonia and alcohols are also observed, but they grow in slowly. A measurement of the relative rate constants for the sequential addition reactions of NH 3 confirms that addition of the fifth NH 3 is at least an order of magnitude slower than the first four attachments. In reactions with acetonitrile and benzene, a maximum of four attachments of these ligands is observed. Sequential halide abstractions with CH 3 X yield Nb 8 C 12 X n + truncating at n ) 4 for X ) Cl and n ) 5 for X ) Br and I. The "titration" results and the relative rate constants for the sequential addition reactions of NH 3 provide supporting evidence that the geometric structure of Nb 8 C 12 + is the theoretically more stable T d or D 2d symmetry having two sets of four equivalent metal sites, as opposed to the T h symmetry with all eight equivalent metals. Finally, the results for Nb 8 C 12 + are compared to those previously obtained for V 8 C 12 + and Ti 8 C 12 + .