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Manganese(I) carbonyl complexes bearing a MACHO‐type ligand (HN(CH2CH2PR2)2) readily react in their amido form with CO2 to generate 4‐membered {Mn−N−C−O} metallacycles. The stability of the adducts decreases with the steric demand of the R groups at phosphorous (R=isopropyl>adamantyl). The CO2‐adducts display generally a lower reactivity as compared to the parent amido complexes. These adducts can thus be interpretated as masked forms of the active amido catalysts and potentially play important roles as off‐loop species or branching points in catalytic transformations of carbon dioxide. [ABSTRACT FROM AUTHOR]

The potential of Pd/Pt complexes for catalytic carboxylation of arenes with CO2 is investigated by means of computational chemistry. Recently we reported that the bis[(2‐methoxyphenyl)phosphino]‐benzenesulfonamido palladium complex 1 inserts CO2 reversibly in its Pd−C(aryl) bond generating carboxylato complex 2. In the present work we study how geometric and electronic factors of various ligands and substrates influence the overall activation barrier (energy span, ES) of a potential catalytic cycle for arene carboxylation comprising this elementary step. The tendency of the key intermediates to dimerize and thus deactivating the potential catalysts is examined as well as the role of the base, which inevitably is needed to stabilize the reaction product. We show that Pd and Pt complexes I(Pd)‐L16‐S1 and I(Pt)‐L16‐S1 do not dimerize, enable the computation of complete catalytic cycles, and show interestingly low ES values of 26.8 and 24.5 kcal/mol, respectively. [ABSTRACT FROM AUTHOR]