Synthesis of Chalcogenidoimidodiphosphinato–Rh I Complexes and DFT Investigation of Their Catalytic Activation in Olefin Hydroformylation

The synthesis and spectroscopic characterization of [Rh{R 2 P(S)NP(S)R 2 ‐ S , S′ }(cod)] [cod = 1,5‐cyclooctadiene; R = Ph ( 1 ), i Pr ( 4 )], [Rh{Ph 2 P(S)NP(S)Ph 2 ‐ S , S′ }(CO) 2 ] ( 2 ) and [Rh{Ph 2 P(S)NP(S)Ph 2 ‐ S , S′ }(CO)(PPh 3 )] ( 3 ) is described. The crystal structures of complexes 1 and 3 are also presented. The synthesized Rh I complexes are essentially not catalytically active against olefin hydroformylation, in contrast to the previously reported complex [Rh{Ph 2 P(O)NPPh 2 ‐ P , O }(CO)(PPh 3 )] ( 6 ). Differences in the catalytic activity were interpreted with the aid of a well‐defined DFT‐based protocol involving relativistic effects and dispersion correction. The steric and electronic effects of the Rh I coordination environment with respect to their activation by H 2 are discussed. The results demonstrate that the presence of the more electronegative oxygen atom in the Rh I coordination sphere polarizes the H–H bond and promotes its heterolytic cleavage, thereby leading to the formation of a Rh I –monohydride complex in which the oxygen atom of the ligand is protonated.