Iron complex compounds, anions with pyridine

My co-worker J. Sedlmeier then held the view that the amine-containing iron carbonyl complexes were also ionic compounds (VII, 14, 21). Hence the compound Fe2(CO)4(en)3 (en= 1,2-ethylenediamine) was formulated as [Fe(en)3]2+[Fe(CO)4]2. Systematic investigations revealed that reactions of the iron carbonyls with other nitrogen and oxygen donors likewise involved valency disproportionation of the metal with concomitant formation of mono- and polynuclear carbonylferrates, viz., [Fe(CO)4]2, [Fe2(CO)8]2-, [Fe3(CO)n]2-. R. Werner (VII, 15, 17, 19, 20) even discovered and characterized compounds containing the tetranuclear anion [Fe4(CO)13]2, the first being that from pyridine and iron carbonyl, viz.,... 

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