Hydroformylation ranging from 40°C to 200° C4.

Hydroformylation is a homogenously
catalyzed reaction that is one of the the most relevant processes in the
chemical industry.1 The reaction, also termed the “oxo process”2,
is responsible for the conversion of olefins to aldehydes in the presence of carbon
monoxide and hydrogen. Globally, hydroformylation produces over 2.5 million tons
of aldehyde product per year3. In order to maintain industrial-scale
efficacy, the reaction is catalytically driven4. The most commonly
used catalysts are based on group VIII metals, HRh(CO)(PPh3)3 and HCo(CO)4
5. Rhodium-based catalysts are more widely used. This is due to their regioselectivity
for linear products and greater reactivity5. Typically, this
reaction is run under high pressures and temperatures ranging from 40°C to 200° C4.

Rh-based catalysts, however, are able to operate effectively under milder
conditions5.

 

The mechanism facilitated by HRh(CO)(PPh3)3 is initiated by the dissociation of a phosphine
ligand. An olefin is then able to bind to the open coordination site, and
insert itself into the Rh-hydrogen bond. An alkyl ligand is thus produced via
migratory insertion. Spectroscopic studies show this migration to be the rate
determining step of the process6. As a result of this insertion, a vacant
coordination site is produced allowing CO to ligate to the Rh center. The
complex completes a second migratory insertion whereby the CO inserts into the
Rh-alkyl bond. Following the second insertion, the system undergoes oxidative
addition as two hydrogen atoms bind to open sites on the metal. Finally, the
complex will undergo reductive elimination to produce an aldehyde product and
regenerate the catalyst.