The simplest pentaalkylbismuth(V) compound, pentamethylbismuth (1), was recently prepared by Seppelt et al. (Angew. Chem. Int. Ed. Engl.1994, 33, 976). Bismuth(V) has a very high oxidation potential, and for a long time, therefore, its compounds could only be isolated with the most electronegative bonding partners oxygen and fluorine; the only pentaorganobismuth(V) compounds known were pentaaryl derivatives. After the outstanding preparative achievement of Seppelt et al. theoreticians are challenged: The relationship between the color and the structure of penta-organobismuth(V) compounds is not yet fully understood.

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