[A([18]crown‐6)]₂[Ni(CO)₃]·8NH₃ (A = K, Rb) – An Ammoniate with a Trigonal Planar [Ni(CO)₃]²– Anion

The new carbonyl nickelate salt [ A ([18]crown‐6)] 2 [Ni(CO) 3 ] · 8NH 3 ( A = K, Rb) serendipitously crystallized from a solution of (P Ph 3 ) 2 Ni(CO) 2 , [18]crown‐6, [2.2.2]cryptand, and K 6 Rb 6 Ge 17 in liquid ammonia. The [Ni(CO) 3 ] 2– anion represents the first tricarbonyl compound of nickel characterized by X‐ray diffraction studies and completes the row of known carbonyl metalates. The planar anion displays approximately D 3 h symmetry. The calculated electron localization function (ELF) of the complex shows plane basins above and below the molecular plane and the twofold negative charge is spread over the Ni(CO) 3 entity.