Transition Metal Complex Catalysts for the Oligomerization of Butadiene. II. The Reaction of Catalyst Components

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Abstract
In order to obtain some knowledge on the behavior of catalysts in the oligomerization of butadiene, the reaction between cobalt(III) acetylacetonate or iron(III) acetylacetonate and trietylaluminum has been investigated by means of magnetic susceptibility measurements, infrared spectra, gasometry, and electron spin resonance spectra. When triethylaluminum was added to an excess of cobalt(III) acetylacetonate, the infrared spectra and gasometry suggested that the latter was reduced via stable cobalt(II) acetylacetonate to zero valent cobalt and that, at the same time, the former was transformed into aluminum(III) acetylacetonate. The extraordinarily large magnetic moment (μeff=12) and the absence of the signal of the electron spin resonance spectra suggested the formation of metallic cobalt. The metallic cobalt was active enough to be readily oxidized by the addition of methanol. The addition of butadiene to this solution decreased the magnetic moment to 7.8. This shows some coordination of butadiene to reduced cobalt. When cobalt(III) acetylacetonate was reduced in the presence of an excess of triethylaluminum (Al/Co>4), the zero valent cobalt was stablilized as a result of the formation of a certain diamagnetic complex with triethylaluminum. However, the addition of cobalt(III) acetylacetonate to this reaction mixture decomposed the above complex, and the very large magnetic moment indicated the formation of metallic cobalt. Iron(III) acetylacetonate was, like cobalt(III) acetylacetonate, reduced to zero valent iron via stable iron(II) acetylacetonate. In the presence of an excess of triethylaluminum, however, zero valent iron did not form a stable complex with triethylaluminum, and from the ferromagnetism metallic iron was observed toresult.

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