Transition-metal ethene bonds:: Thermochemistry of M+(C2H4)n (M=Ti-Cu, n=1 and 2) complexes

Complexes of the first-row transition-metal cations (Ti+-Cu+) with one and two ethene molecules are studied by guided ion beam mass spectrometry. Thermalized complexes are formed in a flow tube source and examined by energy-resolved collision-induced dissociation with Xe. The energy dependence of the CID cross sections is analyzed with consideration of multiple collisions, internal energy of the reactants, and lifetime effects. First, D-0(M+-C2H4), and second, D-0(C2H4M+-C2H4), adiabatic metal ion ethene bond energies, in eV, obtained in this study are 1.51 +/- 0.11 for Ti (first bond only), 1.29 +/- 0.08 and 1.32 +/- 0.14 for V, 0.99 +/- 0.11 and 1.12 +/- 0.11 for Cr, 0.94 +/- 0.12 and 0.91 +/- 0.15 for Mn, 1.50 +/- 0.11 and 1.57 +/- 0.16 for Fe, 1.93 +/- 0.09 and 1.58 +/- 0.14 for Co, 1.84 +/- 0.11 and 1.79 +/- 0.15 for Ni, and 1.82 +/- 0.14 and 1.80 +/- 0.13 for Cu, respectively. These values include corrections for diabatic dissociation in the cases of Fe+(C2H4) and Mn+(C2H4)(2), a point that is discussed in detail. Previous work obtained from theory and experiment is then compared with values determined in this study. Periodic trends observed for the mono-and bis-ethene complexes cations are also discussed and compared with the isobaric metal mono-and dicarbonyl cation complexes.