Gas Phase Reactions of the Met-Cars Ti8C12+, Nb8C12+, and Ti7NbC12+ with Acetone and Methyl Iodide

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Gas phase reactions of the metallocarbohedrenes Ti[sub 8]C[sub 12][sup +], Nb[sub 8]C[sub 12][sup +], and Ti[sub 7]NbC[sub 12][sup +] with two different types of molecules, namely, acetone and methyl iodide, are investigated at near thermal energy by employing a laser-induced plasma source coupled with a triple quadrupole mass spectrometer. Two general types of reactions are observed: molecular associations and atom abstraction reactions. In agreement with earlier studies on the interaction of Ti[sub 8]C[sub 12][sup +]/with polar molecules, association reactions are found to dominate in the case of acetone. But, the incorporation of even one Nb greatly affects the reactivity. For example, the extraction of one and two oxygen atoms from acetone is also observed for Nb[sub 8]C[sub 12][sup +] and Ti[sub 7]NbC[sub 12][sup +]; these products are found to sequentially associate with acetone to form Nb[sub 8]C[sub 12][sup +](O)[sub 1[minus]2](acetone)[sub n] and Ti[sub 7]NbC[sub 12][sup +](O)[sub 1[minus]2](acetone)[sub n]. The reaction involves breaking C=O bonds and forming M-O bonds, evidently due to the presence of the dipole-induced charge center of Nb[sub 8]C[sub 12][sup +] and Ti[sub 7]NbC[sub 12][sup +]. Possible reaction mechanisms are proposed which take into account the electronic structures of Nb[sub 8]C[sub 12][sup +], Ti[sub 7]NbC[sub 12][sup +], andmore » Ti[sub 8]C[sub 12][sup +]. 36 refs., 6 figs.« less