Reactions of actinide ions with pentamethylcyclopentadiene: atypical hydrocarbon activation

✍ Scribed by John K. Gibson

• Book ID: 104432041
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 137 KB
• Volume: 202
• Category: Article
• ISSN: 1387-3806
• DOI: 10.1016/s1387-3806(00)00203-7

✦ Synopsis

Gas-phase reactions of 1,2,3,4,5-pentamethylcyclopentadiene (HCp*) with three actinide ions, Np ϩ , Pu ϩ , and Am ϩ , were studied by laser ablation mass spectrometry. The primary goal was to determine if an unusual, non-insertion mode of C-H activation reported for lanthanide ions, Ln ϩ , with this substrate obtains for the homologous actinide ions; the Cp* ligand is central in organoactinide chemistry and the interaction of the quasivalence 5f electrons with HCp* is of special interest. It was found that Np ϩ and Pu ϩ behave similarly to the "reactive" Ln ϩ , and that Am ϩ is similar to the "inert" group of Ln ϩ . For both Ln ϩ and An ϩ , reactivity appears to reflect the energy necessary to excite the ground state metal ion to a configuration with two non-f valence electrons. Evidently Am ϩ , which exhibits a large excitation energy, comparable to those of the inert Ln ϩ , induces C-H activation and single-H 2 -elimination from HCp* by a non-insertion process not seen with other alkenes; this lanthanide-like behavior suggests no distinctive role of the 5f electrons in the Am ϩ -HCp* interaction. Activation by Np ϩ and Pu ϩ of the methyl groups of a tetramethylfulvene intermediate results in double-and triple-dehydrogenation which evidently proceeds by a conventional insertion process involving a C-An ϩ -H complex, in accord with the relatively small Np ϩ and Pu ϩ excitation energies. Results for reactions of AnO ϩ with HCp* revealed an enhanced dehydrogenation activity of NpO ϩ compared with LnO ϩ , which may be a result of the greater accessibility of high oxidation states at the Np metal center. (Int