Oxidation Chemistry of Inorganic Benzene Complexes.

The oxidation of the 28 VE cyclo-E6 triple-decker complexes [(CpR Mo)2 (μ,η6 :η6 -E6 )] (E=P, CpR =Cp(2 a), Cp*(2 b), CpBn (2 c)=C5 (CH2 Ph)5 ; E=As, CpR =Cp*(3)) by Cu+ or Ag+ leads to cationic 27 VE complexes that retain their general triple-decker geometry in the solid state. The obtained products have been characterized by cyclic voltammetry (CV), EPR, Evans NMR, multinuclear NMR spectroscopy, MS, and structural analysis by single-crystal X-ray diffraction. The cyclo-E6 middle decks of the oxidized complexes are distorted to a quinoid (2 a) or bisallylic (2 b, 2 c, 3) geometry. DFT calculations of 2 a, 2 b, and 3 persistently result in the bisallylic distortion as the minimum geometry and show that the oxidation leads to a depopulation of the σ-system of the cyclo-E6 ligands in 2 a-3. Among the starting complexes, 2 c is reported for the first time including its preparation and full characterization.