| Abstract
| - Room-temperature ionic liquids are used as cosolvents in the palladium-catalyzedtelomerization of butadiene with methanol. The basic catalyst is palladium(II) acetate witheither triphenylphosphine or sodium diphenylphosphinobenzene-3-sulfonate (TPPMS), whichwas reacted with butadiene and methanol at 85 °C. It was found that the addition of severalequivalents of 1,3-dialkylimidazolium salts per palladium leads to complete deactivation ofthe catalyst. It was suspected that the deactivation of the catalyst was due to the formationof highly stable palladium imidazolylidene complexes, but no direct evidence of this specieswas 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 systemsfor the telomerization of butadiene with methanol were obtained. Furthermore, a biphasiccatalytic system composed of palladium(II) acetate, TPPMS, heptane, and 1-butyl-2,3-dimethylimidazolium bis((trifluoromethyl)sulfonyl)imidate, [BMMI][TF2N], was used. In thiscase, after the telomerization reaction, the methoxyoctadiene products were recovered bysimple decantation and the ionic liquid phase reintroduced to the reactor. In this way thecatalyst was recycled four times (to total turnover number of 10 000) with little loss of activity.
- The telomerization of methanol/butadiene catalyzed by palladium in the presence of phosphine was studied in various solvent systems including different types of ionic liquids. A biphasic, heptane/ionic liquid solvent system based on a 1,2,3-trialkylimidazolium salt maintained its performance over several cycles without formation of palladium black.
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