[Ni(CO)₄]⁺ as Ni^I Synthon: Synthesis and Characterization of Ni^I Half‐Sandwich and Sandwich Cations

Abstract The stable, easily accessible salt [Ni(CO) 4 ] + [F{Al(OR F ) 3 } 2 ] − (R F =C(CF 3 ) 3 ) was used as a Ni I synthon to generate the novel half‐sandwich complexes [Ni(arene)(CO) 2 ] + (arene=C 6 H 6 , o ‐dfb=1,2‐F 2 C 6 H 4 ). By irreversible removal of CO from the equilibrium, even the rather endergonic reaction to a [Ni( o ‐dfb) 2 ] + salt was successful (Δ r G ° (solv) =+78 kJ mol −1 ). The latter displays an unprecedented slipped η 3 , η 3 ‐sandwich structure and is the ultimate synthon to Ni I ‐chemistry.