Carbon-carbon bonds with CO2: Insights from computational studies
In this mini-review, we provide an overview of recent computational studies on homogeneous transition metal-catalyzed carbon-carbon bond formation with CO2. We cover substitution and addition reactions involving different metals (mainly Ni, Rh, Cu) and substrates (alkanes, alkenes, alkynes, arenes) with focus on the mechanistic details. The CO2 insertion step is generally found to be rate-limiting. The reported transition state geometries for C-C bond formation mostly display three-membered cyclic arrangements involving the metal and the two reacting carbon atoms, except for reaction with Csp atoms, where acyclic conformations are observed. Other reported exceptions point to that an interaction of CO2 with the metal catalyst may not be essential. Several studies suggest that Lewis acid additives could help activating CO2 during C-C bond formation.