Activated Mn‐MACHO Complexes Form Stable CO2 Adducts

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.