Reactivity of bis(g6-arene) derivatives of titanium, vanadium and niobium with fulvenes bearing electron-withdrawing substituents

The reaction of M(g6-arene)2 (M = Ti, arene = MeC6H5; M = V, Nb, arene = 1,3,5-Me3C6H3) with "pentacarbomethoxycyclopentadiene" (pcmcpH), 1-benzoyl-6-hydroxy-6-phenyl fulvene (dbcpH), and 1-benzoyl-3-nitro-6-hydroxy-6-phenyl fulvene (dbncpH) proceeds with evolution of dihydrogen and oxidation of the metal to coordination compounds containing O,O0-coordinated cyclopentadienyl anions, i.e., [pcmcp]-, [dbcp]-, and [dbncp]-, respectively. Complexes of general formula M(O,O0-anion)3, where the metal is in the +III oxidation state, have been isolated for titanium and niobium. In the case of vanadium, different compounds have been obtained depending on the fulvene and the reaction conditions. In particular, solvated derivatives of vanadium(II) of general formula V(O,O0-anion)2(THF)2 have been prepared in THF whereas V(O,O0-anion)2 complexes have been isolated in toluene even in the presence of excess fulvene.