Synthesis of Unprecedented 4d/4f-Polypnictogens

A series of 4d/4f-polyarsenides, -polyarsines and -polystibines was obtained by reduction of the Mo-pnictide precursor complexes [{Cp^t Mo(CO)₂ }₂ (μ,η^2:2 -E₂ )] (E=As, Sb; Cp^t =tBu substituted cyclopentadienyl) with two different divalent samarocenes [Cp*₂ Sm] and [(Cp^Me4nPr )₂ Sm]. For the reductive conversion of the Mo-stibide only one product was isolated, featuring a planar tetrastibacyclobutadiene moiety as an unprecedented ligand for organometallic compounds. For the corresponding Mo-arsenide a tetraarsacyclobutadiene and a second species with a side-on coordinated As₂ ^2- anion was isolated. The latter can be considered as reaction intermediate for the formation of the tetraarsacyclobutadiene.