α,β-Unsaturated diimines as substrates in catalytic C–H activation reactions and as ligands in iron carbonyl complexes

The reaction of 3-[4-(3-oxo-propenyl)-phenyl]-propenal with two equivalents cyclohexylamine as well as the treatment of cyclohexane-1,4-diamine or bis-(4-aminocyclohexyl)-methane with two equivalents of cinnamaldehyde leads to the formation of the corresponding diimines. Mono- or dinuclear iron carbonyl complexes are produced if the diimines are reacted with iron carbonyls. Two of these complexes have been characterized by X-ray crystallography showing that one or two of the α,β-unsaturated imine side chains are coordinated by an iron tricarbonyl moiety in a η4-fashion. The packing is realized by intermolecular C–H⋯O contacts. The same diimines are used as the substrates in ruthenium catalyzed C–H activation reactions together with carbon monoxide and ethylene to produce bis-dihydropyrrolone derivatives in almost quantitative yields.