Gas-phase metal ion ligation: Collision-induced dissociation of Fe(N-2)(x)(+) (x=1-5) and Fe(CH2O)(x)(+) (x=1-4)

Thresholds for collision-induced dissociation of Fe(N-2)(x)(+) (x = 1-5) and Fe(CH2O)(x)(+) (x = 1-4) with xenon are measured by using guided ion beam mass spectrometry. Values for the 0 K (N-2)(x-1)Fe+-N-2 bond energies (in eV) are determined to be 0.56 +/- 0.06, 0.86 +/- 0.09, 0.47 +/- 0.06, 0.56 +/- 0.04, and 0.64 + 0.04 for x = 1-5, respectively. Values for the 0 K (CH2O)(x-1)Fe+-CH2O bond energies (in eV) are determined to be 1.43 +/- 0.07, 1.79 +/- 0.08, 1.06 +/- 0.05, and 0.83 +/- 0.06 for x = 1-4, respectively. The bond energy for Fe+-Xe is determined as 0.47 +/- 0.08 eV. The results for the singly ligated species are in good agreement with values in the literature. These bond energies are compared with those for several other FeL(x)+ series including previously published values for Fe(CO)(x)(+) (x = 1-5), which are reevaluated in light of theoretical information. The observation that the relative bond strengths vary nonmonotonically with the number of ligands is discussed in terms of spin conservation and ligand field theory.