Low Oxidation State Iron(0), Iron(I), and Ruthenium(0) Dinitrogen Complexes with a Very Bulky Neutral Phosphine Ligand

The synthesis of a series of iron and ruthenium complexes with the ligand P2P3Cy, P­(CH2CH2PCy2)3 is described. The iron(0) and ruthenium(0) complexes Fe­(N2)­(P2P3Cy) (1) and Ru­(N2)­(P2P3Cy) (2) were synthesized by treatment of [FeCl­(P2P3Cy)]+ and [RuCl­(P2P3Cy)]+ with an excess of potassium graphite under a nitrogen atmosphere. The Fe­(I) and Ru­(I) species [Fe­(N2)­(P2P3Cy)]+ (3) and RuCl­(P2P3Cy) (4) were synthesized by treatment of [FeCl­(P2P3Cy)]+ and [RuCl­(P2P3Cy)]+ with 1 equiv of potassium graphite under a nitrogen atmosphere. The cationic dinitrogen species [Fe­(N2)­H­(P2P3Cy)]+ (6) and [Ru­(N2)­H­(P2P3Cy)]+ (7) were formed by treatment of 1 and 3, respectively, with 1 equiv of a weak organic acid. The iron­(II) complex Fe­(H)2(P2P3Cy) (5) was also synthesized and characterized. Complexes [RuCl­(P2P3Cy)]­[BPh4], 1, 2, 3­[BPh4], 4, 5, 6­[BF4], and 7­[BF4] were characterized by X-ray crystallography. The Fe­(I) and Ru­(I) complexes 3 and 4 were characterized by electron paramagnetic resonance (EPR) spectroscopy, and the Fe­(I) complex has an EPR spectrum typical of a metal-centered radical.