Oxidation Chemistry of Inorganic Benzene Complexes

The oxidation of the 28 VE cyclo-E-6 triple-decker complexes [((CpMo)-Mo-R)(2)(mu,eta(6):eta(6)-E-6)] (E = P, Cp-R = Cp(2a), Cp*(2b), Cp-Bn(2c)= C-5(CH2Ph)(5); E = As, Cp-R = 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-E-6 middle decks of the oxidized complexes are distorted to a quinoid ( 2a) or bisallylic ( 2b, 2c, 3) geometry. DFT calculations of 2a, 2b, and 3 persistently result in the bisallylic distortion as the minimum geometry and show that the oxidation leads to a depopulation of the sigma-system of the cyclo-E-6 ligands in 2a-3. Among the starting complexes, 2c is reported for the first time including its preparation and full characterization.