Synthesis of Molybdenum and Tungsten Complexes That Contain Triamidoamine Ligands of the Type (C6F5NCH2CH2)3N and Activation of Dinitrogen by Molybdenum

Moshe Kol, Rhett Kempe, William M. Davis, Richard R. Schrock

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Abstract

Three new ligands of the type (ArNHCH2CH2)3N (Ar = 3,5-bis(trifluoromethyl)phenyl, 2-(trifluoromethyl)-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]C1 (M = Moor W), Mo[N3N](OTf) (M = Moor W), [N3N]M=N (M = Moor W), and {[N3N]Mo=NMe}-(OTf). An X-ray study of Mo[N3N]C1 showed it to be a monomeric distorted trigonal bipyramidal species having a pseudo-C3 symmetry (space group P1, a = 11.265(2) Å, b = 11.371(2) Å, c = 21.805(4) å, a = 82.40(1)°, β = 79.07(1)°, γ = 74.89(1)°, K= 2637.4 Å3, Z = 4, fw = 772.75, ρ(calcd) = 1.946 g/cm3, R = 0.032, Rw = 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)[NaLx] by sodium amalgam under dinitrogen and the latter can be oxidized to the former by ferrocenium triflate or air. [N3N] Mo(N2) [NaLx] 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) Å,b= 18.016(4) Å, c = 16.248(3) Å, β = 98.74(2)°, V= 3913(1) Å3,Z = 4, fw = 922.67, ρ(calcd) = 1.566 g/cm3, R = 0.069, Rw, = 0.072) showed it to be a trigonal bipyramidal complex containing a slightly bent diazenido ligand (Mo-Nα = 1.788(9) Å, Mo-Nα-Nβ = 171.1(8)°, NαNβ-Si = 154(1)°).

Original languageEnglish
Pages (from-to)4382-4390
Number of pages9
JournalJournal of the American Chemical Society
Volume116
Issue number10
DOIs
StatePublished - 1 May 1994
Externally publishedYes

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