Dinitrogen Activation Upon Reduction of a Triiron(II) Complex

Reaction of a trinuclear iron(II) complex, Fe3Br3L (1), with KC8 under N-2 leads to dinitrogen activation products (2) from which Fe-3(NH)(3)L (2-1; L is a cyclophane bridged by three beta-diketiminate arms) was characterized by X-ray crystallography. H-1 NMR spectra of the protonolysis product of 2 synthesized under N-14(2) and N-15(2) confirm atmospheric N-2 reduction, and ammonia is detected by the indophenol assay (yield similar to 30%). IR and Mossbauer spectroscopy, and elemental analysis on 2 and 2-1 as well as the tri(amido)triiron(II) 3 and tri(methoxo)triiron 4 congeners support our assignment of the reduction product as containing protonated N-atom bridges.