The Intermetalloid Clusters [Ni2Bi12]4+ and [Rh2Bi12]4+ – Ionothermal Synthesis, Crystal Structures, and Chemical Bonding

The intermetalloid clusters [M2Bi12]4+ (M = Ni, Rh) were synthesized as halogenido‐aluminates in Lewis‐acidic ionic liquids. The reaction of bismuth and NiCl2 in [BMIm]Cl·5AlCl3 (BMIm = 1‐butyl‐3‐methylimidazolium) at 180 °C yielded black, triclinic (P1) crystals of [Ni2Bi12][AlCl4]3[Al2Cl7]. Black, monoclinic (P21/m) crystals of [Rh2Bi12][AlBr4]4 precipitated after dissolving the cluster salt Bi12–xRhX13–x (X = Cl, Br; 0 < x < 1) in [BMIm]Br·4.1AlBr3 at 140 °C. In the cationic cluster [Ni2Bi12]4+, the nickel atoms center two base‐sharing square antiprisms of bismuth atoms (symmetry close to D4h). The valence‐electron‐poorer rhodium‐containing cluster is a distorted variant of this motif: the terminating Bi4 rings are folded to bicyclic “butterflies“ and the central square splits into two dumbbells (symmetry close to D2h). DFT‐based calculations and real‐space bonding analyses place the intermetalloid units between a triple‐decker complex and a conjoined Wade‐Mingos cluster.