摘要:
AbstractNickel cluster cations, generated in an external source by sputtering with 20 keV Xe+ were transferred to the ICR cell of a Fourier transform mass spectrometer (FTMS), collisionally cooled, and trapped for long time periods. During storage, the chemistry of Nin+ was studied with ethylene and methane in the range n = 1 … 20. Rather than undergoing adsorption as an intact unit, C2H4 was dehydrogenated in the 1.2‐position to yield HCCH adducts Nin(C2H2)m+ with a dramatic size‐specificity: Whereas Nin+ ions proved absolutely inert for n = 1, 3, 4, they were found highly reactive from n = 5 on. Cyclotroning in the presence of C2H4 for up to 40 s, Ni5+ was found to add on a maximum of nine C2H2 ligands. A second “hidden” size‐specific effect was discovered between n = 11 and n = 12, where dehydrogenation intensifies to yield NinC6+ as final products. These are being discussed in terms of close‐packed lattice structures. Finally, the threshold for methane activation by Ni5+ leading to Ni5C+ was determined to be 2.0 ± 0.5 eV.