Olefin hydroformylation, energetics

Figure 9. Energetics of catalytic intermediates in olefin hydroformylation...

It is to be hoped that measurements will be made in the near future which will put more substantial flesh on the skeleton of known bond enthalpy contributions in organo-transition metal compounds, so that a better understanding of the energetics of reactions such as olefin disproportionation (metathesis) and hydroformylation may be achieved. 

There remains one more isomerization to be discussed. The formyl group formed in the hydroformylation of olefins with longer carbon chains need not necessarily be attached to one of the C-atoms having previously formed the double bond but can also be bound to other C-atoms of the carbon chain. This is especially the case if the addition to neither C-atom of the double bond results in the formation of an energetically and steri-cally favored alkylcobaltcarbonyl. As an example internal straight chain olefins may be taken. Under favorable reaction conditions they yield nearly the same isomer distribution as the corresponding terminal olefins do [25]. Another example is ethyl vinylacetate which yields the same reaction products as ethyl crotonate does. 

Olefin insertion into an M-H bond and the reverse process, P-hydrogen elimination (BHE), represent elementary reaction steps that are of fundamental importance to many transition-metal (TM) catalyzed processes, such as hydrogenation, hydroformylation, and olefin polymerization, to mention a few. Correspondingly, there has been much theoretical effort toward characterizing the structural parameters and energetics of the intermediates and transition states [1-8], which complements the large amount of related experimental investigations (see, for example, Refs [9-12], and references therein). 

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