Synthesis of arsenic-rich As(n) ligand complexes from yellow arsenic

The reaction of [{η(5)-Cp′′′Co}(2){μ,η(4:4)-toluene}] with yellow arsenic yields the arsenic-rich As(n) ligand complexes [{Cp′′′Co(μ,η(2:2)-As(2))}(2)] (1), [(Cp′′′Co)(4)(μ(4),η(4:4:2:2:1:1)-As(10))] (2) and [(Cp′′′Co)(3)(μ(3),η(4:4:2:1)-As(12))] (3), which were comprehensively characterized. The molecular structure of 1 show a triple-decker complex with two As(2) units forming the middle-deck; compound 2 contains an all-arsenic As(10) analogue of dihydrofulvalene in the molecular structure. The As(12) ligand in 3 represents the largest As(n) ligand complex reported so far.