Organometallic iron (II) hydrazines and hydrazones — syntheses, characterisations and the X-ray crystal structures of [Fe(η5-Cp)(η6-C6H5NHNH2)]+PF6− and [Fe(η5-Cp)(η6-p-MeC6H4NHNCMe2)]+PF6−

Abstract The three new organometallic hydrazines [Fe(η 5 -Cp)(η 6 -RC 6 H 4 NHNH 2 )] + PF 6 − , CpC 5 H 5 , RH, [ 1 ] + PF 6 − ; m -Me, [ 2 ] + PF 6 − ; p -MeO, [ 3 ] + PF 6 − , were synthesised and characterised. They were obtained in CH 2 Cl 2 by reaction of the hydrazine monohydrate, NH 2 NH 2 ·H 2 O, with the corresponding precursors [Fe(η 5 -Cp)(η 6 -RC 6 H 4 Cl)] + PF 6 − . Similarly to free conventional organic hydrazines, the organometallic hydrazines [ 1 ] + PF 6 − and [ 3 ] + PF 6 − react with acetone affording hydrazones formulated as [Fe(η 5 -Cp)(η 6 -RC 6 H 4 NHNCMe 2 )] + PF 6 − , RH, [ 6 ] + PF 6 − ; p -MeO, [ 7 ] + PF 6 − . Likewise, the two other organometallic hydrazones containing the substituent groups R o -Cl, [ 8 ] + PF 6 − and p -Me, [ 9 ] + PF 6 − were also obtained from their parent hydrazine precursors [ 4 ] + PF 6 − and [ 5 ] + PF 6 − , respectively. All the new compounds were characterised by elemental analysis and IR, UV–vis, 1 H- and 13 C-NMR spectroscopy. The crystalline and molecular structures of [ 1 ] + PF 6 − and [ 9 ] + PF 6 − were determined by single crystal X-ray crystallographic analysis. Both structures show a cyclohexadienyl-like character at the coordinated C 6 ring of the phenylhydrazine and the p -methylphenylhydrazone with a folding angle of 6.0(5) and 7.1(6)°, respectively.