PERMETHYLATED METALLOCENES AS SUITABLE MODELS FOR THE PREPARATION OF ONIUM MONOCATIONS AND DICATIONS

Permethylated metallocenes of the iron subgroup (M = Fe, Ru, Os) have been considered as suitable models for preparing onium mono- and dicat ions. EHM MO calculations of the charge distribution in monocations of the type (C(5)Me(5)MC(5)Me(4)CH(2))(+), homoannular dications of the type [C(5)Me(5)MC(5)Me(3)(CH2)(2)](2+), and heteroannular dications of the type [(C(5)Me(4)CH(2))(2)M)](2+) indicate that the positive charg e is mostly localized at the metal atom (M = Ru, Os and, to a lesser d egree, Fe). This fact was confirmed by X-ray structural studies and th e data of IR, H-1, and C-13 NMR spectroscopy, and electrochemistry. Th e reactivity of the monocations, in particular, interconversion of the odd-electron (17- and 19-electron) metallocenium radical cations and 18-electron metallocenyl carbocations has been studied. A M-C(alpha) s igma-bond (M = Ru, Os) is realized in the mono- and dications. It has been suggested that the metallocenyl carbocations (M = Ru, Os) are in fact metallonium or metallocenonium cations (or dications).