Successive reactions of iron carbonyl cations with methanol

The reactivity of Fe(CO)(n)(+) cations with methanol has been investigated using a triple-cell Fourier transform ion cyclotron resonance apparatus. Su ccessive substitutions of the CO ligands by methanol occur rapidly with sim ilar rates. For it = 3-5 the last CO ligand is not replaced, and the termin al substitution products are FeCO(CH3OH)(n-1)(+). A second reaction pathway is observed for n = 3-5, in which two CO ligands are replaced by one metha nol molecule. This pathway occurs even if the Fe(CO)(n)(+) ions have been r adiatively relaxed before reaction, providing information on the bond energ ies in the product ions. Strong internal energy effects are observed on the reaction rates and branching ratios for further substitution of the interm ediate products. The substitution product Fe(CH3OH)(+) from FeCO+ reacts fu rther, with C-O bond cleavage followed by substitution. The resulting Fe[C- 2, H-7, O-2](+) ion undergoes either isomerization or collisional deactivat ion, then slow association with methanol. The reaction of Fe+, due to excit ed states only, begins with formation of FeOH+ and involves the same final steps as in the preceding case. (Int J Mass Spectrom 199 (2000) 267-285) (C ) 2000 Elsevier Science B.V.