Synthesis of arsenic-rich As ligand complexes from yellow arsenic

The reaction of [{η⁵-Cp'''Co}₂{μ,η^4:4-toluene}] with yellow arsenic yields the arsenic-rich As ligand complexes [{Cp'''Co(μ,η^2:2-As₂)}₂] (1), [(Cp'''Co)₄(μ₄,η^4:4:2:2:1:1-As₁₀)] (2) and [(Cp'''Co)₃(μ₃,η^4:4:2:1-As₁₂)] (3), which were comprehensively characterized. The molecular structure of 1 show a triple-decker complex with two As₂ units forming the middle-deck; compound 2 contains an all-arsenic As₁₀ analogue of dihydrofulvalene in the molecular structure. The As₁₂ ligand in 3 represents the largest As ligand complex reported so far.