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

Isolation and Characterization of the Homoleptic Nickel(I) and Nickel(II) Bis‐benzene Sandwich Cations

A stable salt of the metalloradical [Ni(C₆ H₆ )₂ ]⁺ hitherto unknown in the condensed phase was synthesized from [Ni(CO)₄ ]⁺ [WCA]^- and benzene ([WCA]^- =[F{Al(OR^F )₃ }₂ ]^- ; R^F =C(CF₃ )₃ ). Single crystal XRD reveals a remarkable asymmetrically η³ ,η⁶ -slipped sandwich structure. The magnetic properties of the [Ni(C₆ H₆ )₂ ]⁺ cation were determined in solution and in the gas phase. Oxidation with the synergistic Ag⁺ /0.5 l₂ system led to the salt [Ni(C₆ H₆ )₂ ]²⁺ ([WCA]^- )₂ . All products were fully characterized by means of IR, Raman, NMR/EPR, single crystal and powder XRD.

Synthesis and Characterization of Stable Iron Pentacarbonyl Radical Cation Salts

The open-shell iron pentacarbonyl cation [Fe(CO)5 ].+ was isolated by deelectronation, i.e., the single-electron oxidation of the parent neutral Fe(CO)5 using [phenazineF ].+ as the [Al(ORF )4 ]- and [F-{Al(ORF )3 }2 ]- salt (RF =C(CF3 )3 ; phenazineF =perfluoro-5,10-bis(perfluorophenyl)-5,10-dihydrophenazine). [Fe(CO)5 ].+ [Al(ORF )4 ]- was fully characterized (scXRD analysis, IR, NMR, EPR, 57 Fe spectroscopy, CV and SQUID magnetization study) and, apart from being a compound of fundamental interest, may serve as a precursor for low-valent iron coordination chemistry.