R-CH = CH2+H2+CO→R-CH2-CH2-CHO+R-CH(CH3)-CHO
The catalytic cycle from R2C=CH2 to R2CH-CH2-CHO is shown in the following figure. Each step of the cycle is a basic reaction in organometallic chemistry. Cobalt-containing catalyst intermediates alternate between 18e and 16e species in the cycle, and the reaction of 18e species reduces two electrons (through ligand dissociation, 1.2 inserts coordination olefins, and.
Some steps in the hydroformylation process deserve further explanation. The first step involves the CO dissociation of HCO(CO)4, which is inhibited by high-pressure CO, while the fourth step involves the addition of CO. High pressure is beneficial to the reaction, so it is very important to control the appropriate pressure (200-300atm) for the yield and reaction speed. The second step is the first-order reaction of olefins, which is a slow step (the step that determines the speed). In the third step, the combination of CH2 group and metal is more beneficial to the formation of products than the combination of CR2 group and metal. In the sixth step, the reaction includes the addition of H2. However, high H2 pressure may lead to the addition of intermediate H2 in the third step of 16e, and then the alkane R2ch-CH2-Co (Co) 3+H2 will be eliminated.
16e 18e
R2ch-CH2-co (h) 2 (co) 3 =→ R2ch-CH3+HCO (co) 3 reduction elimination
18e 16e
Therefore, it is very important to control the experimental conditions carefully to achieve the best yield of the target product. The pre-catalyst is metal cluster CO2(CO)8, and the actual catalyst species is 16HCO (co) 3.