Mechanistical studies on C–H activation reactions of benzaldimines using selectively deuterated ligands: synthesis and crystal structures of [μ2-η3-(R)N–CH2–CC–C(H)C(H)–C(H)C(H)]Fe2(CO)6

The reaction of Fe2(CO)9 with imine ligands derived from benzaldehyde leads to the formation of dinuclear iron cluster compounds of the general formula [μ2-η3-N–CH2–CC–C(H)C(H)–C(H)C(H)]Fe2(CO)6 by a C–H activation/1,3-hydrogen shift reaction sequence. Six cluster compounds with alkyl and aryl substituents bound to nitrogen have been synthesised and characterised, five of them also by means of X-ray crystallography. The mechanism of the reaction has been investigated by the use of ligands being selectively deuterated in the 2-position. By several NMR experiments including deuterium spectra it can be demonstrated that the hydrogen/deuterium atom of the activated aromatic C–H bond is transferred to the former imine carbon atom producing a methylene group instead and that this reaction strictly follows an intramolecular pathway.