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Synthesis and characterization carbonyl-tungsten(0)complexes [n,n'-bis(ferrocenylmethylene) ethylenediamine]

Kavaklı, Cüneyt
In this study a bidentate ligand containing two ferrocenyl moieties, N,N'-bis(ferrocenylmethylene)ethylenediamine, was prepared by condensation reaction of ferrocenecarboxyaldehyde and ethylenediamine on refluxing in benzene. The molecule was identified by IR, Raman, UV-VIS, 1H-, 13C-NMR spectroscopies. Then, this bidentate ligand was reacted with pentacarbonylbis-(trimethyl)silylethyne)tungsten(0). The ligand substitution reaction in dichloromethane yielded the new complex, tetracarbonyl [N,N'-bis(ferrocenylmethylene)ethylenediamine]tungsten(0) (W(CO)4(BFEDA)). This new complex was isolated from the reaction solution in the form of orange crystals and fully characterized by elemental analysis, IR, UV-VIS, MS, 1H- and 13C-NMR spectroscopies. As a bidentate ligand, [N,N'-bis(ferrocenylmethylene)ethylenediamine] binds the metal atom in the two cis positions in the pseudooctahedral geometry of the tungsten-complex. Electrochemistry of the tetracarbonyl [N,N'-bis(ferrocenylmethylene)ethylenediamine]tungsten(0) was studied by cyclic voltammetry, and controlled potential electrolysis combined with the UV-VIS spectroscopy. One irreversible oxidation and three reversible oxidations were observed in the cyclic voltammogram. One of these reversible and the irreversible oxidations are attributed to tungsten and the other two reversible oxidations to iron centers. It is found that the two ferrocene groups started communication with each other after formation of tungsten-complex. N,N'-bis(ferrocenylmethylene)ethylenediamine was also reacted with photogenerated pentacarbonyl(tetrahydrofuran)tungsten(0) complex and the pentacarbonyl [N,N'-bis(ferrocenylmethylene)ethylenediamine]tungsten(0) (W(CO)5(BFEDA)) as an intermediate on the route to the tetracarbonyl[N,N'-bis(ferrocenylmethylene)ethylenediamine]tungsten(0) was isolated from the reaction medium in the form of red crystals and