SYNTHESIS AND DECOMPLEXATION OF (ETA-ARENE)(ETA-CYCLOPENTADIENYL)IRON(II) HEXAFLUOROPHOSPHATES USING MICROWAVE DIELECTRIC HEATING

A detailed study of the synthesis of (eta-arene)(eta-cyclopentadienyl) iron(II) hexafluorophosphates has been made using microwave dielectric heating. Reactions were carried out in a conventional 850 W microwave oven in a very simple solid CO2-cooled apparatus. A wide range of are ne ligands were used. The microwave technique reduced the normal react ion times for the AlCl3-mediated ligand exchange with ferrocene (with aluminium powder to prevent ferricinium ion formation) from several ho urs to a few minutes and generally resulted in higher yields. 1,2,4-Tr ichlorobenzene was found to be an excellent solvent for such reactions . A preliminary survey of the efficacy of the type of the metal powder used revealed that zinc and copper were as effective as aluminium, bu t that nickel and tin gave little or no reaction. Better yields were u sually obtained when an excess of ferrocene was used. This was particu larly true of alkylarene ligands where almost quantitative yields were obtained in some cases. The microwave method is particularly suited t o the synthesis of bis and more highly complexed species. Arylamine co mplexes can also be made in high yields. Complexes of triphenylphosphi ne are reported together with a wide range of other arenes. Decomplexa tion of these complexes can be efficiently achieved by a slight varian t of the above microwave procedure. High yields of free ligand were ob tained by irradiating an admixture of the complexes with flaked graphi te.