Dicationic E Chains (E=P, As, Sb, Bi) Embedded in the Coordination Sphere of Transition Metals.

The oxidation chemistry of the complexes [{CpMo(CO) } (μ,η :η -E )] (E=P (A), As (B), Sb (C), Bi (D)) is compared. The oxidation of A-D with [Thia] (=[C H S ] ) results in the selective formation of the dicationic E complexes [{CpMo(CO) } (μ ,η :η :η :η -E )] (E=P (1), As (2), Sb (3), Bi (4)), stabilized by four [CpMo(CO) ] fragments. The formation of the corresponding monocations [A] , [C] , and [D] could not be detected by cyclic voltammetry, EPR, or NMR spectroscopy. This finding suggests that dimerization is fast and that there is no dissociation in solution, which was also predicted by DFT calculations. However, EPR measurements of 2 confirmed the presence of small amounts of the radical cation [B] in solution. Single-crystal X-ray diffraction revealed that the products 1 and 2 feature a zigzag E chain in the solid state while 3 and 4 bear a central E cage with a distorted "butterfly-like" geometry. Additionally, 1 can be easily and reversibly converted into a symmetric and an unsymmetric form.