Cubane‐Like Bismuth‐Iron Cluster: Synthesis, X‐ray Crystal Structure and Theoretical Characterization of the [Bi 4 Fe 8 (CO) 28 ] 4– Anion

The reaction of cyclo ‐Bi 4 [Si(SiMe 3 ) 3 ] 4 ( 1 ) with Na 2 [Fe(CO) 4 ] in the presence of n Bu 4 NCl leads to the formation of the cage compound [ n Bu 4 N] 4 [Bi 4 Fe 8 (CO) 28 ] ( 2 ). According to X‐ray single‐crystal structure analysis, the faces of the tetrahedral Bi 4 core are capped by Fe(CO) 3 moieties in a μ 3 fashion to give a cubanoid Bi 4 Fe 4 framework. The four Fe(CO) 4 fragments are μ 1 ‐coordinated to bismuth, each. With 12 skeletal electron pairs the [Bi 4 Fe 8 (CO) 28 ] 4– anion ( 2a ) is a Bi 4 Fe 4 cubane. The negative charge is localized within cluster 2a according to the NBO analysis of its derivatives. The strength of metal–ligand interactions Bi–μ 3 ‐Fe(CO) 3 is responsible for the size of the cluster's cubic core. NICS computations at the cage centers of considered molecules show that 2a has paratropic character, whereas removal of four μ 1 ‐Fe(CO) 4 fragments from latter causes spherical aromaticity of the modified clusters [Bi 4 Fe 4 (CO) 12 ] 4– ( 2aa ) and [Bi 4 Fe 4 (CO) 12 ] 2+ ( 2ab ), mediated by a Bi 4 cluster π orbital.