Dinitrogen complexes of rhenium(I) and rhenium(II)

Abstract

Dinitrogen complexes of rhenium(I) are prepared by the reaction of benzoylazo-complexes, [Re(NNCOPh)Cl₂(PPh₃)_xL_y](L = monodentate ligand or ½ bidentate ligand; x= 0 or 2, x+y= 3), with certain ligands in boiling methanol. The dinitrogen complexes are of the type trans-[ReCl(N₂)L_xL′_y](L = a variety of organophosphines; L′= L or some other organophosphine, CO or PF₃; x+y= 4). For L = L′= PMe₂Ph the dinitrogen complex has an exceptionally low ν(N₂)(1925 cm^–1). Despite its low ν(N₂), it is not easily reduced and strong Brønsted acids protonate the metal rather than the bound dinitrogen. On oxidation, the dinitrogen complexes form moderately stable paramagnetic cations, e.g., trans-[ReCl(N₂)(Ph₂PCH₂CH₂PPh₂)₂]⁺.