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(ORF )3 }2 ]/0.5 I2 (RF =C(CF3 )3 ) in CO atmosphere. This D2d -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(ORF )3 }2 ] and all products were fully characterized by means of IR, Raman, NMR/EPR, single crystal and powder XRD.