Synthesis of Unprecedented 4d/4f‐Polypnictogens

Abstract A series of 4d/4f‐polyarsenides, ‐polyarsines and ‐polystibines was obtained by reduction of the Mo‐pnictide precursor complexes [{CptMo(CO)2}2(μ,η 2:2‐E2)] (E=As, Sb; Cpt=tBu substituted cyclopentadienyl) with two different divalent samarocenes [Cp*2Sm] and [(CpMe4nPr)2Sm]. 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.