Gas-phase reactivity of lanthanide and actinide cations with the archetypal organometallic complexes Fe(CO)5 and Fe(C5H5)2

The gas-phase reactions of lanthanide (Ln+=La+–Lu+, except Pm+) and actinide (An+=Th+, U+) cations with iron pentacarbonyl, Fe(CO)5, and with ferrocene, Fe(C5H5)2, were studied by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). In the case of Fe(CO)5, the observed primary products were of the type MFe(CO)x+ (M=La, Ce, Pr, Nd, Gd, Tb: x=3; M=Ho, Er, Lu: x=3 and 4; M=Sm, Eu, Dy, Tm, Yb: x=4; M=Th, U: x=2 and 3) and evidence was obtained for the presence of direct LnFe and AnFe bonds in these species. With Fe(C5H5)2 the An+ cations and the majority of the Ln+ cations reacted by metal exchange, yielding Ln and An biscyclopentadienyl ions M(C5H5)2+, while the less reactive Ln+ cations formed the ‘adduct’ ions LnFe(C5H5)2+. The product ion distributions observed with the two organometallic reagents and the reaction efficiencies obtained in kinetics studies both revealed a close relation with the relative stability of the accessible formal oxidation states of the metal cations. A few thermochemical estimates pertaining to the different species formed in the reactions could also be made. Reactivity studies of Ln, Th and U oxide and hydroxide cations with the iron complexes are also reported.