Theoretical study on the mechanism of acetylene hydroformylation catalyzed by a heterobinuclear (CO)4Cr(m-PH2)2RhH(CO)(PH3) complex has been carried out in the framework of density functional theory. Structural features of intermediates and transition states of the associative and dissociative mechanisms and the cooperativity of chromium with rhodium were evaluated. It was found that the dissociative mechanism was predominant. The rate-limiting step is the acetylene insertion step with a free energy barrier of 73.72 kJ/mol at 298.15 K and 101.325 kPa. The acetylene insertion and aldehyde elimination steps are irreversible thermodynamically. The introduction of Cr(CO)4 moiety does not alter the mechanism of acetylene hydroformylation. The orbital interaction between Rh and Cr atoms plays an important role in the whole reaction process.

Key words: heterobinuclear Rh(I)-Cr complex, acetylene, hydroformylation, mechanism, density functional theory