Chasing the Mond Cation: Synthesis and Characterization of the Homoleptic Nickel Tetracarbonyl Cation and its Tricarbonyl‐Nitrosyl Analogue

130 years after Mond discovered the first homoleptic carbonyl complex Ni(CO) 4 , we report on a [Ni(CO) 4 ] .+ salt as the first synthesis of any homoleptic nickel carbonyl cation in the condensed phase. It was prepared by oxidation of nickel metal with the synergistic oxidant Ag[F{Al(OR F ) 3 } 2 ]/0.5 I 2 (R F =C(CF 3 ) 3 ) in CO atmosphere. This D 2d ‐symmetric metalloradical represents the last missing entry among the structurally characterized homoleptic carbonyl cations of Groups 6 to 11. Additionally, the nickel tricarbonyl‐nitrosyl cation [Ni(CO) 3 (NO)] + was obtained by usage of NO[F{Al(OR F ) 3 } 2 ] and all products were fully characterized by means of IR, Raman, NMR/EPR, single crystal and powder XRD.