Unraveling promoter effect in enhancing Rh-catalyzed hydroformylation of formaldehyde

Hydroformylation is one of the most important homogenous reactions, especially formaldehyde hydroformylation is of critical importance for synthesis of ethylene glycol. Due to lack of mechanistic analysis on promoters, we have employed a combined experimental and theoretical approach to reveal the promoter effect in the Rh-catalyzed hydroformylation of formaldehyde. The base promoter was suggested to be a bifunctional promoter. The mechanism of Cl-promoted formaldehyde hydroformylation was established, which significantly different from Cl-free system, and HCHO insertion was illustrated to be the rate-determining step. The distortion/ interaction-activation strain analysis and mechanism calculations of halogen types demonstrate that Clcontaining catalyst has superior promotion effects compare to F, Br, and I-containing systems. The investigation on the effect of Cl coordination number shows that one-coordinated catalyst exhibits lower energy barriers and higher reactivity.