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.