Abstract
The binuclear complexes [Cp*(dppe)FeC≡C-(CH 2 ) x -C≡CFe(dppe)Cp*] (x = 3 (8a), x = 4 (8b)) were prepared by deprotonation of the parent bis(vinylidene) derivatives [Cp*(dppe)-Fe=C=C(H)-(CH 2 ) x -(H)C=C=Fe(dppe)Cp*] [PF 6 ] 2 (x = 3 (7a), x = 4 (7b)). The X-ray crystal structure of 8a revealed that the metal-metal distance (8.706 A) is much shorter that the sum of the bond distances of the Fe-Fe assembly (12.24 A). An X-ray powder diffraction analysis of an amorphous sample shows that the Fe-Fe distance may fall into the wide range 8.50-10.75 A. The resolved separations between the redox processes in the cyclic voltammograms evidenced the through-bridge interaction between the iron centers and enabled computations of the comproportionation constants (K c ) and the molar fractions of the different species 8a n + and 8b n + (n = 0, 1, 2) present in solution. The dicationic complexes 8a[PF 6 ] 2 and 8b[PF 6 ] 2 were prepared in good yield by oxidation of 8a and 8b with 2 equiv of ferrocenium. The IR, Mossbauer, ESR, and UV-vis spectra provided evidence for a small through-bridge interaction between the Fe I I I sites. The NIR spectroscopy study of the MV complexes 8a[PF 6 ] and 8b[PF 6 ] clearly shows that through-bridge electron transfer occurs for both compounds, which well obey Hush's theory.
Published Version
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