Synthesis, structure and hydrolysis of some [( η5-cyclopentadienyl)( η6-arene) iron(II)][PF 6] complexes bearing an imine or a nitrone function in α-position of the arene ligand

Abstract

Condensation between [( η 5-Cp)( η 6-fluorene)Fe] u+ ] 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 [( η 5-Cp)( η 6-fluorenone-anil)Fe] + complexes Ia-g (57–88%) as syn-anti mixtures (ca. 30:70 respectively). [( η 5-Cp)( η 6-diphenylmethane)Fe] + II with nitrosobenzene or nitrosotoluenes gave mixtures of [( η 5-Cp)( η 6-benzophenone- N-phenylnitrone)Fe] + IIa-d and [( η 5-Cp)( η 6-benzophenone-anil(Fe] + IIa-d complexes (ca. 80:20) with good yields (80–92%). Nitrone complexes IIa,c,d were isolated as pure Z-isomer by fractional recrystallisation (22–35%). 2D- 1H, 13C NMR correlation and X-ray analysis were used to identify the new compounds. Owing to the high nitrosobenzene oxidative character, condensation with other [( η 5-Cp)( η 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 [( η 5-Cp)( η 6-fluorenone)Fe] + II (82%) and [( η 5-Cp( η 6-benzophenone)Fe] + III (91%).