Novel Nickel Clusters with Se and Cp′ as Ligands: [Ni 4 Se 2 (CO)BrCp′ 3 ], [Ni 6 Se 4 Cp′ 5 ], [Ni 15 Se 10 (CO) 3 CP′ 8 ], and [Ni 15 Se 10 (CO)Cl 2 Cp′ 8 ]

Metal‐rich cluster compounds having novel structures are formed upon reaction of [NiCp′(CO)Br] (Cp′ = methylcyclopentadienyl) with Se(SiMe 3 ) 2 —the 66‐electron cluster 1 is the presumed reactive intermediate involved in the formation of larger clusters. A total of four complexes were isolated by fractional crystallization. All were characterized by X‐ray structure analysis.