Experimental and Theoretical Studies of Co(CH_4)_x^+ with x = 1-4

Abstract

The sequential bond energies of Co(CH_4)_x^+, x = 1-4, are determined experimentally and theoretically. Collision-induced dissociation studies conducted using a guided ion beam tandem mass spectrometer yield 0 K bond energies of D_o[Co^+-Xe] = 0.85 ± 0.07 eV, D_o[Co^+-CH_4] = 0.93 ± 0.06 eV, D_o[Co(CH_4)^+-CH_4] = 1.00 ± 0.05 eV, D_0[Co(CH_4)_2^+-CH_4] = 0.41 ± 0.05 eV, and D_o[Co(CH-4)_3^+-CH_4] = 0.67 ± 0.06 eV. These numbers are in excellent agreement with ab initio calculations which lead to values of D_e[Co^+-(CH_4)] = 0.93 eV, D_e[Co(CH_4)^+-CH_4] = 1.00 eV, D_e[Co(CH_4)_2+-CH_4] ≈ 0.40 eV, and D_e[Co(CH_4)_3^+-CH_4] ≈ 0.70 eV. We find that the nonmonotonic behavior in the sequential binding energies arises from changes in hybridization at the metal center as the third ligand is bound.