ALKYLRHODIUM TETRACARBONYL DERIVATIVES AS CATALYTIC INTERMEDIATES IN HOMOGENEOUS HYDROFORMYLATION REACTIONS - INFRARED SPECTROSCOPIC STUDY

The rhodium-catalyzed hydroformylation of ethylene in n-tetradecane solution has been monitored by infrared spectroscopic examination of the v(CO) region using a high-pressure cell-autoclave. Diverse rhodiu(l) carbonyl derivatives, including [Rh(CO) 2CI]2, C5H5NRh(CO)2Cl, [CH3CO2Rh(CO)2]2, and C5H7O2Rh(CO)2, generate systems that catalyze the hydroformylation of ethylene under mild conditions (e.g., 35 °C and 20-100 atm total pressure). In each of these systems absorption bands due to an unstable metal carbonyl derivative develop as the hydroformylation reaction proceeds. These absorption bands, which occur at the v(CO) frequencies 211 5 w, 2037 s, 2019 s cm-1, are attributed to an unstable rhodium alkyl, presumably C2H5Rh(CO)4, on the basis of the close agreement between these frequencies and those reported for CH3Co-(CO)4 (2105 w, 2036 m, 2019 vs cm-1). © 1979, American Chemical Society. All rights reserved.