Metal carbon dioxide complex
Aside from the fundamental interest in the coordination chemistry of simple molecules, studies in this field are motivated by the possibility that transition metals might catalyze useful transformations of CO2.
In rare cases, CO2 binds to metals as a Lewis base through its oxygen centres, but such adducts are weak and mainly of theoretical interest.
[citation needed] Transition metal carbon dioxide complexes undergo a variety of reactions.
Metallacarboxylic acids protonate at oxygen and eventually convert to metal carbonyl complexes: This reaction is relevant to the potential catalytic conversion of CO2 to fuels.
[5] N-heterocyclic carbene (NHC) supported CuI complexes catalyze carboxylation of organoboronic esters.
Copper tert-butoxide can transmetallate with the organoboronic ester to generate the CuI-C bond, which intermediate can insert into CO2 smoothly to get the respective carboxylate.
Iwasawa and co-workers reported direct carboxylation by styrenyl C-H activation generating coumarin derivatives.
Similar to Cu(I) chemistry mentioned above, Rh(I) complexes can also transmetallate with arylboronic esters to get aryl rhodium intermediates, to which CO2 is inserted giving carboxylic acids.
Rh(I) undergoes oxidative addition to aryl C-H bond followed by transmetallation with alkyl aluminum species.
[24][25][26] Iwasawa and co-workers developed Rh(I) catalyzed carbonation reaction initiated by Rh-H insertion to vinylarenes.
In order to regenerate reactive Rh-H after nucleophilic addition to CO2, photocatalytic proton-coupled electron transfer approach was adopted.
