Ligand exchange cationic sandwiches

Iron, Ruthenium, and Osmium.—MO-INDO calculations have been carried out 353 foj. cations of the type [CpFe( y-arene)]+. The e.s.r. spectra of the 17-electron dications [CpFe( -arene)] + and 19-electron neutral complexes of the type [CpFe( -naphthalene)] have been discussed, and the Fe Mossbauer spectra of salts [CpFe( y-arene)]+ [PFg]" have been analysed. Ligand-exchange reactions of Cp Fe with pyrene in the presence of AlaCle-Al have given various mixed-sandwich complexes in which a (CpFe)+ residue is attached to one or both of the benzenoid rings of pyrene itself and of its di- and tetra-hydro deriva-... 

This type of sandwich complex, first reported with iron as the central metal, has now become widespread with ruthenium as well. Early routes to ruthenium complexes were modeled on iron chemistry, and used the AICI3-catalyzed exchange of a cyclopentadienyl ligand for an arene in ruthenocene, or reaction of CpRu(CO)2Cl with AlCb/arene. These methods are less successful with ruthenium than with iron, however, owing to the greater stability of ruthenocene. A mixture of arene, pentamethylcyclopentadiene, and RuCls in the Zn reduction method gives good yields of the mixed-sandwich cations. A... 

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