Dedicated to Rolf Huisgen in admiration of his inspiring work on physical organic chemistry Fourier-transform ion-cyclotron-resonance mass spectrometry is used to investigate the reactions of massselected homo-and heteronuclear clusters MM' (M, M' Fe, Co, Ni) with linear alkanenitriles. The reactions with pentanenitrile are examined in detail by means of deuterium-labeling studies. In comparison to the previously studied atomic cations Fe , Co , and Ni , the diatomic cluster cations react more specifically and only insert in CÀH bonds in the initial step, whereas the bare ions M activate both CÀH and CÀC bonds. Like for the atomic cations, dehydrogenation proceeds via remote functionalization of the terminal positions of the substrate, although H-scrambling processes, preceding dehydrogenation, are more pronounced for the dinuclear cluster cations. The Ni-containing cluster cations CoNi and Ni 2 are unique in that they bring about double dehydrogenation as well as activation of CÀC bonds subsequently to the first dehydrogenation. The latter kind of reaction is also partly observed for the [ Introduction. ± Exploitation of the distinct chemical character of transition metals, owing to their unique electronic configuration, constitutes the basis of heterogeneous catalysis. Although the d-block elements offer a wide variety of catalytic properties, this versatility is confronted with an enormous number of chemical problems, which often prevent the realization of a catalytic sequence. Variation of surface textures and the combination of different transition metals are, among others, possible means to enhance the performance and to enlarge the number of given catalytic systems. For example, synergistic effects of different transition metals proved to bring about efficient CÀN coupling reactions in gas-phase experiments with bimetallic cluster cations not being achieved by their homonuclear analogues [1]. Because surface defects often constitute the active sites for chemical reactions, support-free transition-metal clusters may serve as a model to study the intrinsic properties of catalysts. As demonstrated earlier, gas-phase studies provide a powerful experimental approach to assess the inherent reactivities of the cluster ions under well-defined conditions without being obscured by difficult-to-control solvation, aggregation, counterions, and other effects [2]. Finally, combinations of different transition metals are used not only in homogeneous and heterogeneous catalysis [3], but often also in, e.g., metallo-proteins to accomplish specific chemical reactions for a given substrate [4].