Synthesis of molybdenum and tungsten complexes that contain triamidoamine ligands of the type (C6F5NCH2CH2)3N and activation of dinitrogen by molybdenum

Article abstract of DOI:10.1021/ja00089a028

Three new ligands of the type (ArNHCH₂CH₂)₃N(Ar = 3,5-bis(trifluoromethyl)phenl,2-(trifluomethyl)-phenyl, and pentafluorophenyl) have been prepared. Only Mo and W complexes containing the [(C₆F₅NCH₂CH₂)₃N] ^3- ([N₃N]^3-) ligand were found to be stable. Stable complexes that have been prepared include Mo[N₃N](NMe₂), M[N₃N]Cl (M = Mo or W), Mo[N₃N](OTf) (M = Mo or W), [N₃N]M≡N (M = Mo or W), and {[N₃N]Mo=NMe}-(Otf). An X-ray study of Mo[N₃N]Cl showed it to be a monomeric distorted trigonal bipyramidal species having a pseudo-C₃ symmetry (space group P1, a = 11.265(2) ?, b = 11.371(2) ?, c = 21.805(4) ?, α = 82.40(1)°, β = 79.07(1)°, γ = 74.89(1)°, V = 2637.4 ?³, Z = 4, fw = 772.75, ρ(calcd) = 1.946 g/cm³, R = 0.032, R_w = 0.034). Reduction of Mo[N₃N](OTf) with 1 equiv of sodium amalgam yields a dinuclear bridging dinitrogen species, [N₃N]-Mo(μ-N₂)Mo[N₃N]. In the presence of 2 equiv of sodium amalgam in ether Mo[N₃N](Otf) is reduced to [N₃N]-Mo(N₂) [Na(ether)_x] (1 < x < 2). A more stable 15-crown-5 derivative can be prepared and more fully characterized. [N₃N]Mo(μ-N₂)Mo[N₃N] can be reduced to [N₃N]Mo(N₂)[NaL_x] by sodium amalgam under dinitrogen and the latter can be oxidized to the former by ferrocenium triflate or air. [N₃N]Mo(N₂)[NaL_x] reacts with Mo[N₃N](OTf) to give [N₃N]Mo(μ-N₂)Mo[N₃N], with triisopropylsilyl chloride to give [N₃N]MoN=NSi(i-Pr)₃, and with tributyltin chloride to give [N₃N]MoN=NSn(Bu)₃. An X-ray study of [N₃N]MoN=NSi(i-Pr)₃(space group P2₁/n, a= 13.524-(3) ?, b = 18.016(4) ?, c = 16.248(3) ?, β = 98.74(2)°, V = 3913(1) ?³ = 4, fw = 922.67, ρ(calcd) = 1.566 g/cm³, R = 0.069 R_w = 0.072) showed it to be a trigonal bipyramidal complex containing a slightly bent diazenido ligand (Mo-N_α = 1.788(9) ?, Mo-N_α-N_β = 171.1(8)°, N_α-N_β-Si = 154(1)°).