Novel diazadienes based on 1,3,4-oxadiazines: Ligands in iron carbonyl complexes and substrates in catalytic [2+2+1] cycloaddition reactions

N,N′-(4-methyl-4H-1,3,4-oxadiazine-5,6-diylidene)-bis-aniline derivatives react with Fe2(CO)9 to give dinuclear iron carbonyl complexes. One of the iron atoms is bonded symmetrically to both exocyclic imine nitrogen atoms. The second iron atom shows a side-on coordination towards the Cdouble bond; length as m-dashN bond next to the oxadiazine oxygen atom. In addition, the iron atoms are connected via a metal metal bond. The same oxadiazine derivatives produce chiral spiro-lactams in a ruthenium catalyzed formal [2+2+1] cycloaddition reaction with carbon monoxide and ethylene.