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 Fe-2(CO)(9) with imine ligands derived from benzaldehyde leads to the formation of dinuclear iron cluster compounds of the general formula [mu 2-eta 3-N-CH2-C=C-C(H)=C(H)-C(H)]Fe-2(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. (C) 1999 Elsevier Science S.A. All rights reserved.