Isolation of Dysprosium and Yttrium Complexes of a Three-Electron Reduction Product in the Activation of Dinitrogen, the (N2)3- Radical

Dyl(2) reacts with 2 equiv of KOAr (OAr = OC6H3(CMe3)(2)-2,6) under nitrogen to form not only the (N-2)(2-) complex, [(ArO)(2)(THF)(2)Dy](2)(mu-eta(2):eta(2)-N-2) 1, but also complexes of similar formula with an added potassium ion, [(ArO)(2)(THF)Dy](2)(mu-eta(2):eta(2)-N-2)[K(THF)(6)], 2, and [(ArO)(2)(THF)Dy](2)(mu(3)-eta(2):eta(2):eta(2)-N-2)K(THF), 3. The 1.396(7) and 1.402(7) angstrom N-N bond distances in 2 and 3, respectively, are consistent with an (N-2)(3-) ligand, but the high magnetic moment of 4f(9) Dy3+ precluded definitive identification. The Y[N(SiMe3)(2)](3)/K reduction system was used to synthesize yttrium analogues of 2 and 3, {[(Me3Si)(2)N](2)(THF)Y}(2)(mu-eta(2):eta(2)-N-2)[K(THF)(6)] and {[(Me3Si)(2)N](2)(THF)Y}(2)(mu(3)-eta(2):eta(2):eta(2)-N-2)K, that had similar N-N distances and allowed full characterization. EPR, Raman, and DFT studies are all consistent with the presence of (N-2)(3-) in these complexes. N-15 analogues were also prepared to confirm the spectroscopic assignments. The DFT studies suggest that the unpaired electron is localized primarily in a dinitrogen pi orbital isolated spatially, energetically, and by symmetry from the metal orbitals.