Carbon Dioxide Catalyzed Cyclometallation of a Carbene Complex: Synthesis and Mechanism

Abstract

The reaction of the nucleophilic carbene complex [Ph2P(S)(SO2Ph)C=Ru(p‐cymene)] (1) with carbon dioxide is reported. Instead of forming an activation product by 1,2‐addition of the C–O bond across the M=C bond, selective cyclometallation is observed. This metallation occurs at the phenyl group of the thiophosphoryl moiety and is thus in contrast to previously reported cyclometallations at the sulfonyl unit. DFT calculations demonstrate that the ease and selectivity of the reaction can be explained by a unique mechanism in which CO2 is coordinated by the carbene ligand. The thus formed carboxylate facilitates C–H activation and proton transfer to the former carbene center to re‐liberate CO2.

Manganese(I) Tricarbonyl Complexes with Bidentate Pyridine-Based Actor Ligands: Reversible Binding of CO2 and Benzaldehyde via Cooperative C–C and Mn–O Bond Formation at Ambient Temperature

“…The authors propose that owing to the reversible MLC bonding, CO 2 serves as a catalyst and gives rise to the high selectivity of this reaction demonstrating the catalytic utilization of such a reversible binding mode. 39 Beyond the cooperative activation of the C� O double bond of CO 2 , the reversible bonding scheme (A) was extended to other multiple bonds involving carbonyl 40,41 (F) and nitrile moieties (G,H) and has been exploited in catalyzed conjugate addition reactions encompassing, for instance, C−C 20,42 and C−O 43,44 couplings. A recent example of great elegance was reported by Greb and co-workers where the reversible ML-cooperative addition of CO 2 and carbonyl moieties was transferred to a p-block element, specifically to a constrained, square-planarly coordinated, aluminum(III) complex with a meso-octamethylcalix [4]pyrrolato ligand (F).…”

“…An intriguing reaction pathway was proposed by Gessner and co-workers, where reversible addition of CO 2 to a ligand-centered C-nucleophile gives rise to transient carboxylate species, which directs a subsequent C–H activation of an adjacent phenyl group. The authors propose that owing to the reversible MLC bonding, CO 2 serves as a catalyst and gives rise to the high selectivity of this reaction demonstrating the catalytic utilization of such a reversible binding mode . Beyond the cooperative activation of the CO double bond of CO 2 , the reversible bonding scheme ( A ) was extended to other multiple bonds involving carbonyl , ( F ) and nitrile moieties ( G,H ) and has been exploited in catalyzed conjugate addition reactions encompassing, for instance, C–C , and C–O , couplings.…”