Activation of Carbon Dioxide by CoCDn- (n = 0-4) Anions.

Laser ablation generated CoCDn- (n = 0-4) anions were mass selected and then reacted with CO2 in an ion trap reactor. The reactions were characterized by mass spectrometry and quantum chemical calculations. The experimental results demonstrated that the CoC- anion can convert CO2 into CO. In contrast, the bare Co- anion is inert toward CO2. Coordinated D ligands can modify the reactivity of CoCD1-4- in which CoCD1-3- can reduce CO2 into CO selectively and CoCD4- can only adsorb CO2. The crucial roles of the coordinated C and D ligands to tune the reactivity of CoCDn- (n = 0-4) toward CO2 were rationalized by theoretical calculations. Note that the hydrogenation process that is usually observed in the reactions of gas-phase metal hydrides with CO2 is completely suppressed for the reactions CoCDn- + CO2. This study provides insights into the molecular-level origin for the observations that CO can be selectively generated from CO2 catalyzed by cobalt-containing carbides in heterogeneous catalysis.