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

A stable salt of the metalloradical [Ni(C 6 H 6 ) 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(CF 3 ) 3 ). Single crystal XRD reveals a remarkable asymmetrically η 3 ,η 6 -slipped sandwich structure. The magnetic properties of the [Ni(C 6 H 6 ) 2 ] + cation were determined in solution and in the gas phase. Oxidation with the synergistic Ag + /0.5 l 2 system led to the salt [Ni(C 6 H 6 ) 2 ] 2+ ([WCA] - ) 2 . All products were fully characterized by means of IR, Raman, NMR/EPR, single crystal and powder XRD.