The reaction of cerium (IV) isopropoxide with triethylaluminum in cyclooctatetraene gives the reported air-sensitive, brown-black microcrystalline compound. The compound shows a single signal in* H NMR at 5.9 ppm in THF-t/g or at 5.75 ppm in toluene-tfg. When the toluene solution of the complex was exposed to air, the brown solution became pale yellow and the NMR contained only one peak at 5.61 ppm, which is the resonance for neutral cyclooctatetraene. The infrared spectrum agrees with that re-ported. Conversion of bis ([8] annulene) cerate (III) 5 ion to cerocene can beaccomplished electrochemically. The reversible half-wave potential for the Ce (IV)/Ce (III) couple in this system is-1.28 V vs. NHE6 and is, to our knowledge, the lowest Ce (IV)/Ce (III) couple reported. 7 This observation suggested thatbis ([8]-annulene) cerate (III) ion could be chemically converted to cerocene with mild oxidizing agents; indeed, we found that shaking a THF solution with excess silver iodide gives quantitative conversion to cerocene. This simple procedure is clearly the preparation of choice.

Cerocene reacts slowly with UC14 to give uranocene; this be-havior is similar to that of thorocene and unlike the bis (7r-[8]-annulene) lanthanate (III) anions that react rapidly with UC14. Cerocene also hydrolyzes in wet THF more slowly than thorocene to produce a mixture of 80% 1, 3, 5-and 20% 1, 3, 6-cyclooctatrienes. 8 This reactivity pattern does not suggest an ionic cluster.