SYNTHESIS OF MOLYBDENUM AND TUNGSTEN COMPLEXES THAT CONTAIN TRIAMIDOAMINE LIGANDS OF THE TYPE (C6F5NCH2CH2)(3)N AND ACTIVATION OF DINITROGEN MOLYBDENUM

Three new ligands of the type (ArNHCH2CH2)(3)N (Ar = 3,5-bis(trifluoro methyl)phenyl, 2-(trifluoromethyl)phenyl, and pentafluorophenyl) have been prepared. Only Mo and W complexes containing the [(C6F5NCH2CH2)(3 )N](3-) ([N3N](3-)) ligand were found to be stable. Stable complexes t hat have been prepared include Mo[N3N](NMe(2)), 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 distort ed trigonal bipyramidal species having a pseudo-C-3 symmetry (space gr oup P (1) over bar, a = 11.265(2) Angstrom, b = 11.371(2) Angstrom, c = 21.805(4) Angstrom, alpha = 82.40(1)degrees, beta = 79.07(1)degrees, gamma = 74.89(1)degrees, V = 2637.4 Angstrom(3), Z = 4, fw = 772.75, rho(calcd) = 1.946 g/cm(3), R = 0.032, R(W) = 0.034). Reduction of Mo[ N3N](OTf) with 1 equiv of sodium amalgam yields a dinuclear bridging d initrogen species, [N3N]Mo(mu N-2)Mo[N3N]. In the presence of 2 equiv of sodium amalgam in ether Mo[N3N](OTf) is reduced to [N3N]Mo(N-2)[Na( ether)(x)] (1 < x < 2). A more stable 15-crown-5 derivative can be pre pared and more fully characterized. [N3N]Mo(mu-N-2)Mo[N3N] can be redu ced to [N3N]Mo(N-2)[NaL(x)] by sodium amalgam under dinitrogen and the latter can be oxidized to the former by ferrocenium triflate or air. [N3N]Mo(N-2)[NaL(x)] reacts with Mo[N3N](OTf) to give [N3N]Mo(mu-N-2)M o[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 s tudy of [N3N]MoN=NSi(i-Pr)(3) (space group P2(1)/n, a 13.524(3) Angstr om, b = 18.016(4) Angstrom, c = 16.248(3) Angstrom, beta = 98.74(2)deg rees, V = 3913(1) Angstrom(3), Z = 4, fw = 922.67, rho(calcd) = 1.566 g/cm(3), R = 0.069, R(W) = 0.072) showed it to be a trigonal bipyramid al complex containing a slightly bent diazenido ligand (Mo-N-alpha = 1 .788(9) Angstrom, Mo-N-alpha-N-beta = 171.1(8)degrees, N-alpha-N-beta- Si = 154(1)degrees).