Solution and Gas-Phase Reactivity of Me₁₂ Fe₈^- and Related Cluster Ions

The cluster ion Me₁₂ Fe₈^- is an unprecedented representative of organoiron species, which are of great interest because of their possible role as intermediates in iron-catalyzed cross-coupling reactions. To learn more about its behavior in solution, the possible formation of related cluster ions, and their reactivity, electrospray-ionization mass spectrometry and gas-phase experiments were performed. Me₁₂ Fe₈^- adopts a highly dynamic behavior in solution and disappears in the presence of the chelating ligand N,N,N',N'-tetramethylethylenediamine. Besides homoleptic Me₁₂ Fe₈^- , its heteroleptic analogues Me_12-n Fe₈ Ph_n^- , n=1-5, are also accessible. Me₁₂ Fe₈^- undergoes iron-halogen exchange reactions with aryl halides. These substrates, as well as their alkyl counterparts, mediate the formation of new homoleptic cluster ions up to Me₁₈ Fe₁₂^- . In contrast, no evidence was found for oxidative additions or related reactions. Gas-phase fragmentation of the cluster ions results in numerous different reactions, ranging from the loss of single methyl radicals to the reductive elimination of MePh.