Structural Diversity of Mixed Polypnictogen Complexes: Dicationic EE' (E ≠ E' = P, As, Sb, Bi) Chains, Cycles and Cages Stabilized by Transition Metals

The reactivity of the tetrahedral dipnictogen complexes [{CpMo(CO)}(μ,η:η-EE')] (E, E' = P, As, Sb, Bi; "") towards different one-electron oxidation agents is reported. Oxidation with [Thia][TEF] (Thia = CHS ; TEF = Al{OC(CF)} ) leads to the selective formation of the radical monocations [MoEE']˙, which immediately dimerize to the unprecedented dicationic EE' ligand complexes [{CpMo(CO)}(μ,η:η:η:η-E'EEE')] E-E bond formation. Single crystal X-ray diffraction revealed that, in the case of and , P-P bond formation occurs yielding zigzag EP (E = As (), Sb ()) chains, whereas forms a SbBi () cage, an unprecedented AsSb unit representing an intermediate stage between a chain- and a cage-type structure, and a novel planar AsBi () cycle. Therefore, bear the first substituent-free, dicationic hetero-E ligands, stabilized by transition metal fragments. Furthermore, in the case of , the exchange of the counterion causes changes in the molecular structure yielding an unusual, cyclic AsSb ligand. The experimental results are corroborated by DFT calculations.