Dinitrogen-divanadium complexes with triamidoamine ligands, 1-3, were synthesized and characterized by resonance Raman, UV-vis, and NMR spectroscopy and elemental and X-ray structure analyses. X-ray structure analyses reveal that all three of the complexes have a dimeric structure with a μ-N ligand (N-N bond length 1.200-1.221 Å). Resonance Raman and NMR spectra of 1-3 in solution show that these complexes maintain a dimeric structure in benzene and toluene solutions. N NMR spectra of 1 and 3 have peaks assignable to μ-N ligands at 33.4 and 27.6 ppm, respectively, but 2 does not have a similar peak under the same conditions. In V NMR spectra, the peaks of vanadium ions were observed at -173.3, -143.8, and -240.2 ppm, respectively, which are in a higher magnetic field region in comparison to those of dinitrogen-divanadium complexes reported previously. The structure and electronic properties of 1 are supported by DFT calculations. Additionally, all complexes react with excess amounts of M[CH] (M = Na, K) and the proton sources HOTf, HCl, and [LutH]OTf (Lut = 2,6-dimethylpyridine) to produce ammonia without hydrazine. The ammonia produced was evaluated as an ammonium salt by H andN NMR spectroscopy. The yield of NH produced in the reaction of 1 with Na[CH] and HOTf under N was 151% (per V atom).

A novel dinitrogen–dichromium complex, [{Cr(LBn )}2(μ-N2)] (1), has been prepared from reaction of CrCl3 with a lithiated triamidoamine ligand (Li3LBn ) under dinitrogen. The X-ray crystal structure analysis of 1 revealed that it is composed of two independent dimeric Cr complexes bridged by N2 in the unit cell. The bridged N–N bond lengths (1.188(4) and 1.185(7) Å) were longer than the free dinitrogen molecule. The elongations of N–N bonds in 1 were also supported by the fact that the ν(N–N) stretching vibration at 1772 cm–1 observed in toluene is smaller than the free N2. Complex 1 was identified to be a 5-coordinated high spin Cr(IV) complex by Cr K-edge XANES measurement. The 1H NMR spectrum and temperature dependent magnetic susceptibility of 1 indicated that complex 1 is in the S = 1 ground state, in which two Cr(IV) ions and unpaired electron spins of the bridging N2 2– ligand are strongly antiferromagnetically coupled. Reaction of complex 1 with 2.3 equiv of Na or K gave chromium complexes with N2 between the Cr ion and the respective alkali metal ion, [{CrNa(LBn )(N2)(Et2O)}2] (2) and [{CrK(LBn )(N2)}4(Et2O)2] (3), respectively. Furthermore, the complexes 2 and 3 reacted with 15-crown-5 and 18-crown-6 to form the respective crown-ether adducts, [CrNa(LBn )(N2)(15-crown-5)] (4) and [CrK(LBn )(N2)(18-crown-6)] (5). The XANES measurements of complexes 2, 3, 4, and 5 revealed that they are high spin Cr(IV) complexes like complex 1. All complexes reacted with a reducing agent and a proton source to form NH3 and/or N2H4. The yields of these products in the presence of K+ were higher than those in the presence of Na+. The electronic structures and binding properties of 1, 2, 3, 4, and 5 were evaluated and discussed based on their DFT calculations.