Chiral diazadiene and β-ketoimine ligands from the reaction of N,N′-bis-aryl-oxalimidoylchlorides with (S)-prolinol and their reactivity towards iron carbonyls

N,N′-Bis-aryl-oxalimidoylchlorides react with (S)-prolinol to give chiral N,N′-bis-aryl-tetrahydropyrrolo-[2,1-c][1,4]oxazine-3,4-diylidenediamines. These compounds exhibit a 1,3-diazadiene subunit which may be reacted either with Fe(CO)5 under photochemical or with Fe2(CO)9 under thermal reaction conditions to yield dinuclear complexes of the general formula (ligand)Fe2(CO)6. In these complexes an unsymmetrical binding mode of the Fe2(CO)6 moiety is realized. One of the iron atoms is coordinating both imine nitrogen atoms, whereas the second iron atom is connected to one of the CN double bonds in a side-on fashion. If the aromatic substituent of the oxalimidoylchloride is p-OCH3C6H4 the reaction with Fe(CO)5 or Fe2(CO)9 produces a mixture of diastereomers. In all other cases the (S)-configuration of the starting material is retained. If the aromatic substituent is p-BrC6H4 the corresponding tetrahydropyrrolo-[2,1-c][1,4]oxazine derivative undergoes a quantitative rearrangement reaction to produce the isomeric 2-(4-bromphenyl)-3-(4-bromphenylimino)-tetrahydropyrrolo[1,2-a]pyrazine-4-one. The reaction of this ligand with Fe(CO)5 or Fe2(CO)9 ends up in the formation of a complex of the general formula [(ligand)3Fe][(μ2-H)Fe3(CO)11]2 consisting of an octahedrally coordinated Fe2+ and two triangular [(μ2-H)Fe3(CO)11] anions.