The Mechanism, Catalysts, and Ligands

It is interesting to note that the original mechanism for the hydroformylation of monoolefins (1-pentene, methyl acrylate) suggested by Heck and Breslow [6] 

HCo(CO)4 can be prepared directly from Co2(CO)g under hydroformylation conditions [11]. Alternatively, other precursors, particularly tvater-soluble salts such as Co(OAc)2, Co(HCOO)2, or Co(ethylhexanoate)2, have been suggested for technical scale processes. These Co salts are reduced to Co under the effect of H2. The catalyst formation can be accelerated by the addition of aqueous non-miscible alcohols such as 2-ethylhexanol or isononanol [12]. The generation from water-soluble Co salts is especially useful for the preparation of cobalt catalysts anchored on heterogeneous surfaces [13]. 

In technical processes, the Co catalyst is frequently oxidized after completion of the hydroformylation with oxygen or air to give Co salts [14]. The latter can be easily extracted with water ( decobalting ) [15]. 

In terms of complex stability, phosphines with strong a-donor properties are advantageous. Noteworthy, the p/Cj value of tertiary phosphines correlates indirectly with the rate of the hydroformylation [18]. Thus, the coordination of 

The hydroformylation with Co catalysts modified with sulfonated phosphines (e.g., TPPTS (trisodium salt of 3,3, 3 -phosphinidynetris(benzenesulfonic acid))) in water maybe advantageously utilized for the recycling of the metal [26]. Residual cobalt concentrations of 6-70 ppm are left in the organic phase finally. Such 

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