Cationic Iridium(￥°) Complex of Ethyl Cinnamate and Hydrogenation of Unsaturated Esters with Iridium(￥°)-Perchlorato Complex

摘要

Reaction of Ir(ClO4)(CO)(PPh3)2 with trans-C6H5CH = CHCO2C2H5 produces a new cationic iridium(グ) complex, [Ir (trans-C6H5CH = CHCO2C2H5)(CO)(PPh3)2]ClO4 where trans-C6H5CH = CHCO2C2H5 seems to be coordinated through the carbonyl oxygen rather than through the ヰ-system of the olefinic group according to the spectral data. It has been found that Ir(ClO4)(CO)(PPh3)2 catalyzes the hydrogenation of CH2 = CHCO2C2H5, trans-CH3CH = CHCO2C2H5 and trans-C6H5CH = CHCO2C2H5 to CH3CH2CO2C2H5, CH3CH2CH2CO2C2H5 and C6H5CH2CH2CO2C2H5, respectively at room temperature under the atmospheric pressure of hydrogen. The relative rates of the hydrogenation of the unsaturated esters are mostly understood in terms of steric reasons.