The reactions of CpZr(CH(3))(3), 1, and Cp(2)Zr(CH(3))(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state (1)H and (13)C NMR using (13)C-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma-alumina(500), leading to several surface structures. Correlation between EXAFS and (13)C NMR data suggests, in short, two main surface structures having different environments for the methyl group: [Al](3)-OZrCp(CH(3))(2) and [Al](2)-OZrCp(CH(3))(mu-CH(3))-[Al] for the monoCp series and [Al](2)-OZrCp(2)(CH(3)) and [Al]-OZrCp(2)(mu-CH(3))-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.

Room-temperature ionic liquids are used as cosolvents in the palladium-catalyzed telomerization of butadiene with methanol. The basic catalyst is palladium(II) acetate with either triphenylphosphine or sodium diphenylphosphinobenzene-3-sulfonate (TPPMS), which was reacted with butadiene and methanol at 85 °C. It was found that the addition of several equivalents of 1,3-dialkylimidazolium salts per palladium leads to complete deactivation of the catalyst. It was suspected that the deactivation of the catalyst was due to the formation of highly stable palladium imidazolylidene complexes, but no direct evidence of this species was obtained. On the basis of this hypothesis, the use of pyridinium and 1,2,3-trialkylimidazolium salts was studied in an attempt to limit the formation of such species. It was found, particularly for the 1,2,3-trialkylimidazolium salts, that highly active and selective systems for the telomerization of butadiene with methanol were obtained. Furthermore, a biphasic catalytic system composed of palladium(II) acetate, TPPMS, heptane, and 1-butyl-2,3-dimethylimidazolium bis((trifluoromethyl)sulfonyl)imidate, [BMMI][TF2N], was used. In this case, after the telomerization reaction, the methoxyoctadiene products were recovered by simple decantation and the ionic liquid phase reintroduced to the reactor. In this way the catalyst was recycled four times (to total turnover number of 10 000) with little loss of activity.