Conversion of hydrazides into N,N′-diacylhydrazines in the presence of a ruthenium(ii)–arene complex

Abstract

Mono and dinuclear p-cymene-ruthenium(II) complexes [RuCl(L¹)(η⁶-p-cymene)]Cl, where L¹ is propionic acid hydrazide (1) and [Ru₂Cl₂(L²)(η⁶-p-cymene)₂], where H₂L² is N¹,N²-dipropionylhydrazine (2), were prepared by a reaction of [RuCl₂(η⁶-p-cymene)]₂ with the corresponding ligand precursor. Upon the reaction of [RuCl₂(η⁶-p-cymene)]₂ with butyric acid hydrazide and pentanoic acid hydrazide in a 1 : 1 molar ratio in situ formation of tetradentate bridging ligands, N¹,N²-dibutanoylhydrazine and N¹,N²-dipentanoylhydrazine, respectively, occurred and the dinuclear complexes [Ru₂Cl₂(L³)(η⁶-p-cymene)₂] (3) and [Ru₂Cl₂(L⁴)(η⁶-p-cymene)₂] (4) were isolated. The compounds were characterised by elemental analysis, ESI-mass spectrometry, IR and 1D and 2D NMR spectroscopies. The structures of all complexes were established using single crystal X-ray crystallography. According to these data in both the mono- and dinuclear complexes the ruthenium atoms adopt the usual “three-leg piano-stool” geometry which is common for this type of complexes. Combining DFT calculations with the characterisation of the final products using X-ray diffraction, a possible reaction mechanism was discussed.