Synthesis, structure and hydrolysis of some [(eta(5)-cyclopentadienyl)(eta(6)-arene)iron(II)][PF6] complexes bearing an imine or a nitrone function in alpha-position of the arene ligand

Condensation between [(eta(5)-Cp)(eta(6)-fluorene)Fe](+)] I and various nitrosoarenes R-Ph-NO (R = H, 2-Me, 3-Me, 4-Me, 3-COMe, 4-COMe and 4-NMe(2)) were initiated with 5% t-BuOK and led to [(eta(5)-Cp)(eta(6)-fluorenone-anil)Fe](+) complexes Ia-g (57-88%) as syn-anti mixtures (ca. 30:70 respectively). [(eta(5)-Cp)(eta(6)-diphenylmethane)Fe](+) II with nitrosobenzene or nitrosotoluenes gave mixtures of [(eta(5)-Cp)(eta(6)-benzophenone-N-phenylnitrone)Fe](+) IIa-d and [(eta(5)-Cp)(eta(6)-benzophenone-anil)Fe](+) IIa-d complexes (ca. 80:20) with good yields (80-92%). Nitrone complexes IIa,e,d were isolated as pure Z-isomer by fractional recrystallisation (22-35%). 2D-H-1, C-13 NMR correlation and X-ray analysis were used to identify the new compounds. Owing to the high nitrosobenzene oxidative character, condensation with other [(eta(5)-Cp)(eta(6)-arene)Fe](+) complexes (arene = toluene, ethylbenzene, indane and tetraline) failed. Acidic hydrolysis of these imine and nitrone complexes has been investigated kinetically using polarography. Macroscale hydrolysis yielded [eta(5)-Cp)(eta(6)-fluorenone)Fe](+) Ii (82%) and [(eta(5)-Cp)(eta(6)-benzophenone)Fe](+) IIi (91%).