Organometallic tetravalent cerium

Evans, W.J., Deming, T.J., and Ziller, J.W. (1989) The utility of ceric ammonium nitrate-derived alkoxide complexes in the synthesis of organometallic cerium(lV) complexes. Synthesis and first X-ray crystallographic determination of a tetravalent cerium cyclopentadienide complex, (C5H5)3Ce(OCMe3). Organometallics, 8, 1581. 

Borsini, et al.,f ] reported the use of a redox catalyst system for the polymerization of ethylene and chlorotrifluoroethylene. One advantage of this catalyst system was that it permitted operation at lower temperatures than with peroxides. It allowed production of polymers with a linear chain, an orderly distribution of the asymmetric points. This process had favorable economics due to the possibility of the recovery of the catalyst, followed by its oxidation and recycle. The catalytic system was comprised of an organometallic compound and tetravalent cerium salt in quantities ranging from 0.01 to 2 of the former and 0.001 to 1 of metallic cerium part by weight per hundred parts by weight of the monomer mixture. This catalyst allowed the polymerization reaction to be conducted in the range of -60 to 20°C. Examples of the catalytic system include Pb(C2H5)4 and (NH4)2Ce(N03)g. 

Cerium is the only lanthanide metal with areadily accessible tetravalent oxidation state. Synthesis and molecular structure determination of organometallic Ce(IV) complexes are of interest and a challenge, because the Ce(IV) ion is strongly oxidizing and the anionic ligands typically... 

Gulino, A., Casarin, M., Conticellio, V.P. etal. (1988) Efficient synthesis, redox characteristics, and electronic structure of a tetravalent tris(cyclopentadienyl)cerium alkoxide complex. Organometallics, 1, 2360. 

Even flien well-characterized coordination compoimds are limited to only a few classes of compounds. Notable are, e.g., halogeno complexes and complexes of oxo acids, p-diketonates and related SchifF-base complexes, as well as porphyrinates and related complexes. Two other important classes of cerium(lV) compounds, the alkoxides and amides of Ce" +, can be regarded as pjewfifo-organometallics and are discnssed together with the organocerium(IV) complexes in Tetravalent Chemistry OrganometalUc. 

Cerium is the only lanthanide element forming tetravalent compounds, stable in aqueous solutions, because the ion Ce + has the electron configuration of the ideal gas xenon. Despite the very strong oxidizing power of the Ce cation, several organometallic compounds have been reported to have an astonishingly high stability. 

---