Selective insertion of oxygen and selenium into an electron-precise aramagnetic selenium-manganese carbonyl cluster [Se₆Mn ₆(CO)₁₈]^4-

(Figure Presented) The facile synthesis of a novel electron-precise paramagnetic hexamanganese carbonyl selenide cluster [Se₆Mn ₆(CO)₁₈]^4- (1 ) was discovered, which demonstrates contrasting reactivity toward O₂ and Se₈ under markedly mild conditions to afford the O- and Se-inserted clusters [Se₆Mn₆(CO)₁₈(O)]^4- (2) and [Se ₁₀Mn₆(CO)₁₈]^4- (3), respectively. Clusters 1-3 represent the first examples of electron-precise paramagnetic main-group transition metal carbonyl clusters, and their formation and bonding properties are further elucidated by theoretical calculations.