Triazenido Ligand Research Articles

Stabilization of Aryl–Calcium, –Strontium, and –Barium Compounds by Designed Steric and π‐Bonding Encapsulation

Pentafluorophenyl complexes of the heavier alkaline-earth metals (Ca, Sr, Ba) are stabilized by a novel sterically crowded triazenido ligand. The pendent arene rings of the aryl-substituted triazenide are π bonded to the alkaline-earth metal atoms, thereby suppressing decomposition pathways or ligand redistribution reactions and allowing the isolation of solvent-free derivatives (see picture; Ba: green; N: blue; F: light green; C: gray).

Synthesis and Structure of K[Cd(O2N‐C6H4‐NNN‐C6H4‐NO2)3], an Anionic 1, 3‐Bis(4‐nitrophenyl)triazenido Complex of Cadmium

AbstractThe reaction of cadmium acetate in methanol with 1, 3‐bis(4‐nitrophenyl)triazene in THF in the presence of KOH yields K[Cd(O2NC6H4NNNC6H4NO2)3] in form of hexagonal prismatic, red crystals with the trigonal space group R3¯ and a = 12.229(2), c = 48.988(10) Å and Z = 6. In the anionic cadmium complexes, which are located along the threefold axis, the Cd atoms are coordinated in a trigonal prismatic arrangement by the atoms N(1) and N(3) of three triazenido ligands. The potassium cations are coordinated icosahedrally by oxygen atoms of each one nitro group of six neighbouring anionic complexes. The Cd‐N distances are 2.376(4) and 2.350(4) Å, and the K‐O distances are in the range of 2.833(6) to 3.365(6) Å.

Synthesis and characterization of chelate and bridging triazenide complexes of palladium and platinum. Stereoselective oxidative addition of chlorine or iodine to [NBu4][Pt(C6F5)2(η2-PhNNNPh)

The triazenide complexes cis-[M(C6F5)2(η2-ArNNNAr)] − (M = Pd, Pt; Ar = C6H5, C6H4Me-p), anti-[{Pd(C6F5)(L)(μ-PhNNNPh)}2] [L = PPh3, t-BuNC, PhCN, tht (tht = SC4H8, tetrahydrothiophene)] and anti-[{Pd(C6F5)(Br)(μ-PhNNNPh)}2]2− have been prepared by treatment of the corresponding precursors [{M(C6F5)2(μ-OH)}2]2− (M = Pd, Pt), [{Pd(C6F5)(L)(μ-X)}2] (X = OH or Cl) and [{Pd(C6F5)(Br)(μ-Br)}2]2− with either ArNNNHAr or ArNNNAr−. The stereoselective oxidation of cis-[Pt(C6F5)2(PhNNNPh)]− with PhICl2 or I2 leads to the synthesis of the corresponding mononuclear platinum(IV) complex cis,trans-[Pt(C6F5)2(PhNNNPh)(X)2]− (X = Cl or I). The crystal structures of cis-[Pd(C6F5)2(η2-PhNNNPh)]−, anti-[{Pd(C6F5)(t-BuNC)(μ-PhNNNPh)}2] and cis,trans-[Pt(C6F5)2(η2-PhNNNPh)(Cl)2]− have been established by X-ray diffraction. The Pd⋯Pd distance bridged by the rigid triazenido ligands in anti-[{Pd(C6F5)(t-BuNC)(μ-PhNNNPh)}2] is 2.9907(8) A where a boat conformation of the central ‘Pd2N6’ eight-membered ring is observed. The [Pt(C6F5)2(η2-PhNNNPh)(Cl)2]− anion shows an octahedral arrangement around the platinum atom, involving two trans-chloro ligands, two cis-C6F5 groups and a chelating triazenide.

Reaction of [Et 3NH][(μ-RE)(μ-CO)Fe 2(CO) 6] (E=S, Se) with azides. Synthesis of (μ-RE)(μ-p-R 1C 6H 4N 3H)Fe 2(CO) 6 and crystal structure of (μ-Bu tS)(μ-PhN 3H)Fe 2(CO) 6

The reaction of [Et 3NH][(μ-RE)(μ-CO)Fe 2(CO) 6] (E=S, Se) ( 1) with aryl azides gives bridging triazenido complexes (μ-RE)(μ-p-R 1C 6H 4N 3H)Fe 2(CO) 6 ( 2– 8) ( 2, RE=Bu t S, R 1=H; 3, RE=PhS, R 1=H; 4, RE=Bu t S, R 1=Cl; 5, RE=Bu t S, R 1=MeO; 6, RE=PhS, R 1=MeO; 7, RE=PhSe, R 1=H; 8, RE=PhSe, R 1=Cl). These complexes were characterized by elemental analyses and 1H-NMR and IR spectroscopy. The structure of complex 2, established by single-crystal X-ray diffraction analysis, shows that the triazenido ligand binds to two iron centers in a bridging bidentate fashion.

SERS application in elucidation of the nature of homologue Cu(I) triazenido complexes

The reaction of the neutral 1,3-diphenyltriazenide derivative PhNHNNPh with [(PPh 3) 2Cu(CH 3COO)] 2 leads to a mixture of different coordinated Cu(I) complexes (TPPC), in contrast to the homologue complexes containing bidentate triazenido ligands, [(PPh 3)Cu(TolNNNTol)] 2 and [(PPh 3) 2Cu(XC 6H 4NNNC 6H 4Y)], X=Y=Et, X=H, Y=Me. The SERS spectrum of the reaction product reveals the strong enhancement of the ν(NN) mode, characteristic to the monodentate ligand, in contrast to the commonly enhanced band ν s(NNN) of the related studied complexes with bidentate triazenido ligands. The complete analysis of the SERS spectrum elucidates the nature of the mixed Cu(I) triazenido complexes in the reaction product and strongly suggests the presence of the main complex, with monodentate coordinated Cu(I), adsorbed on the Ag surface.

FT-Raman studies on new triphenylphosphin-copper(I) triazenido complexes

The reaction of neutral triazenides HL, L= p-XC 6H 4NNNC 6H 4Y- p, X=Y=CH 3 (1), C 2H 5 (2), and X=CH 3, Y=H (3), with [(PPh 3) 2Cu(CH 3COO)] 2, Ph = C 6H 5 in boiling methanol yields new triphenylphosphin-copper I) triazenido complexes: [(PPh 3)CuL] 2, X = Y = CH 3 ( 1′), and [(PPh 3) 2CuL], X = Y = C 2H 5 ( 2′) and X = CH 3, Y = H ( 3′). The Raman spectra of the protonated ligand ( 1–3) and the new corresponding Cu(I) complexes ( 1′–3′) are discussed in comparison. The observed changes in position and band intensities of the FT-Raman spectra confirm the coordination of deprotonated triazenido ligand to the Cu(I) centers.

Formation of the Digallium Compound [(C5C6)2N3](R)Ga–Ga(R)[N3(C6H5)2] with Two Bis(trimethylsilyl)methyl Groups and Two Terminal Chelating Diphenyltriazenido Ligands

AbstractTetrakis[bis(trimethylsilyl)methyl]digallane (4) 1 reacts with 1,3‐diphenyltriazene to yield two compounds, which were both characterized by a crystal structure determination. The gallium–gallium bond is retained in the yellow derivate [(H5C6)2N3](R)Ga–Ga(R)[N3(C6H5)2 2 [R = CH(SiMe3)2], which is formed by a ligand exchange reaction and shows two terminal chelating triazenido ligands besides two bis(trimethylsilyl)methyl groups; the GaGa bond length is 245.79(6) pm. The second product is the orange dialkyl(diphenyltriazenido)gallium derivative R2Ga[N3(C6H5)2] 3, where the triazene has reacted as an oxidant by the cleavage of the GaGa bond and probably by release of elemental hydrogen.

Synthesis and characterization of triazenido and amidino complexes of nickel and palladium

The reaction of LiPhN(Y)NPh [Y = N or C(Ph)] with [MX 2L 2] (M = Ni, Pd; X = Cl, Br, mesityl; L = PEt 3, a; PMe 2Ph, b; PPh 3; PBz 3, d) has been studied. With Y = N complexes containing the triazenido ligand as monodentate [MX(NNN)L 2] (Ni: 1; Pd: 2), bidentate [MX(NNN)L] (Ni: 3; Pd: 4) and bridging two metal atoms [M(μ-NNN)L 2] 2(ClO 4) 2 (Ni: 5; Pd: 6) have been prepared. However, when Y = C(Ph) only palladium derivatives having the bridging amidino group [Pd(μ-NCN)XL] 2 ( 7) can be obtained. These complexes have been characterized by IR, 1H and 31P NMR spectroscopy.

ChemInform Abstract: 1,3‐Bis(4‐fluorophenyl)triazenido Complexes of Copper and Silver. Synthesis and Structure of (Cu(F‐C6H4N3C6H4‐F))4, (Ag(F‐C6H4N3C6H4‐F))4, and (Cu(F‐C6H4N3C6H4‐F) (OCH3))4.

AbstractIn both tetrameric complexes (III) (space group C2/c, Z=4) the four metal(I) atoms form a planar rhombus the edges of which are bridged alternately above and below by the triazenido ligands.

Synthesis of 1,3-diphenyltriazenide complexes of aluminium, gallium and indium: Crystal structure of tris(1,3-diphenyltriazenido)aluminium(III)

The reaction of AlMe 3 with 1,3-diphenyltriazene [Hdpt] in toluene gives Al(dpt) 3, even when AlMe 3 is in large excess. The monomeric structure has been established by X-ray diffraction. Crystals of Al(dpt) 3 are monoclinic, space group C2/ c with a = 20.587(3), b = 16.005(3), c = 13.236(3) Å and β = 119.172(12)°, Z = 4, R = 0.067 and R w = 0.083. The aluminium(III) is coordinated by three chelating triazenido ligands to give a trigonally distorted octahedral geometry. The gallium and indium analogues are also reported.

Synthese und Struktur von 1,3-Bis(4-trifluormethylphenyl)triazenido-Komplexen des Kupfer(I) und Silber(I) / Synthesis and Structure of 1,3-Bis(4-trifluormethylphenyl)triazenido Complexes of Copper(I) and Silver(I)

[(F3CC6H4NNNC6H4CF3)Cu]4 (1) and [(F3CC6H4NNNC6H4CF3)Ag]n (2) are obtained by the addition of a solution of CuCl or AgNO, in CH3CN to a solution of Na(F3CC6H4NNNC6H4CF3) in THF. Recrystallization of 1 in toluene/n-hexane yields air-stable orange crystals (tetragonal space group P4̄21c, lattice constants a - 1527.7(5), c = 1281.3(4) pm, Z = 2). Complex 1 forms tetrameric units of symmetry S4 with the four Cu atoms forming a slightly folded rhombus. The triazenido ligands bridge the Cu atoms alternatingly above and below the rhombic Cu4 ring resulting in short Cu -Cu interactions of 257.9 pm. Complex 2 crystallizes from pyridine/methanol in form of yellow, air-stable crystals exhibiting a weak temperature independent paramagnetism of 0.64 B.M. per Ag atom at room temperature. The lattice constants are a = 2943(2), b = 475.8(5), c = 2280(1) pm. β = 111.99(6)°. Z = 8 for the monoclinic space group P21/c. The Ag atoms form zigzag chains with short Ag-Ag distances of 283.4 and 284.0 pm and angles Ag-Ag-Ag of 113.7 and 114.1°. The bridging triazenide ligands are arranged alternatingly above and below the Ag-Ag chain. Two symmetry independent zigzag chains are found in the unit cell.

Synthese und Kristallstruktur von [l,3-Bis(4-ethoxyphenyl)triazenido]pyridino-silber(I), einem dimeren Komplex mit kurzem Silber-Silber-Kontakt / Synthesis and Crystal Structure of [1,3-Bis(4-ethoxyphenyl)triazenido]pyridino Silver(I), a Dimeric Complex with a Short Silver-Silver Contact

1,3-Bis(4-ethoxyphenyl)triazenido silver(I) (1) is obtained from equimolar amounts of the triazenido anion and AgNO3 in THF/CH3CN. 1 forms in pyridine the dimer [Ag(EtOC6H4NNNC6H4OEt)·py]2 (2) which crystallizes as yellow pyridine solvate 2·2 py in the monoclinic space group P21/n and a = 1067.1(7), b = 1764.5(9), c = 1373.0(9) pm, β = 106.46(7)°, Z = 2. In the centrosymmetric dimer 2, two triazenido ligands bridge two Ag(I) atoms with their atoms N1 and N3 forming an eight-membered heterocycle Ag2N6 with a short Ag-Ag interaction of 272.6 pm. To each Ag atom an additional pyridine ligand is weakly coordinated with a distance Ag-N40 = 245.5 pm. The bond axis N1 - Ag-N3′ within the heterocycle is not linear (158.5°). The Ag-N distances to the N-atoms of the triazenido ligand are 217.6 and 218.5 pm.

The crystal and molecular structure of trans-bis(triphenylphosphine)dicarbonyl(1,3-di-p-tolyltriazenido)rhenium(I)

Abstract The structure of trans-bis(triphenylphosphine)dicarbonyl(1,3-di-p-tolyltriazenido)rhenium(I) has been determined from three-dimensional X-ray diffraction data collected by counter methods. The compound crystallizes in the triclinic space group P 1 with a = 15.62(1), b = 14.25(1), c = 12.48(1) A, α = 66.34(4)°, β = 108.84(4)°, and γ = 115.48(4)°; ϱx = 1.46 g cm−3 for Z = 2. The structure was refined to the final R index of 0.056. The coordination about the rhenium atom is approximately octahedral. The triazenido ligand is coordinated to the metal atom in a bidentate mode with a N(1)ReN(3) angle of 57(1)° and a N(1)N(2)N(3) angle of 105(1)°. The ReN(1) and ReN(3) bond lengths are 2.21(1) and 2.18(1) A and the N(1)N(2) and N(2)N(3) distances are 1.33(1) and 1.31(1) A, respectively. The entire rheniumtriazenido system is essentially planar, indicative of π delocalization over the whole system.

1,3-Diaryltriazenido complexes of bis-cyclopentadienylmolybdenum. Preparation and electrochemical behaviour

The new complexes [Mo(η-C 5H 5) 2( p-R 1C 6H 4NNN- p-C 6H 4R 2)][PF 6] ( 1) (R 1 = R 2 = H, F, CH 3, OCH 3; R 1 = H, R 2 = CH 3, OCH 3; R 1 = CH 3, R 2 OCH 3) have been prepared. The electrochemical behaviour of these complexes in acetonitrile has been studied by cyclic voltammetry and constant potential electrolysis at platinum electrodes. The complexes undergo two reversible one-electron reductions to species which are stable on the cyclic voltammetry time scale, but the uptake of electrons appears to be followed by loss of the triazenido ligand. The oxidative electrochemistry of the complexes can be rationalized in terms of a disproportionation occurring after the first one-electron oxidation. Both reduction and oxidation potentials show good linear correlations with σ + Hammett parameters, providing evidence for the mesomeric influence of ligand R 1 and R 2 substituents on the metal orbitals involved in the redox processes.

Isostructural triazenido complexes of first row transition metals. Part 2. Synthesis and properties of [(?5-C5H5)L(RN3R)CoIII]PF6, L = PEt3, PPh3, P(OMe)3 and P(OPh)3

The synthesis and properties of the [(η5-C5H5)L(RN3R)CoIII]PF6 complexes, with L = PEt3, PPh3, P(OMe)3 or P(OPh)3, are reported. A six coordinate configuration containing a chelating triazenido ligand is proposed which is isostructural with the known complexes of iron and nickel. The spectroscopic properties of the isoelectronic Co and Fe complexes, (η5-C5H5)L(RN3R)M, are compared in relation to the charge on the central metal atom. The complex with L = CO could not be prepared, but the carbonyl inserted product (η5-C5H5)(L{RNNN(R)C(O)}Co was isolated. In one of the reactions, the novel ring-bound triphenylphosphine complex, [η5-C5H5)(η5-C5H4PPh3)CoIII](PF6)2, was isolated as a side product. The mechanism of this reaction is discussed.

Isostructural triazenido complexes of first row transition metals. Part 1. Synthesis and properties of (?5-C5H5)(L)(RN3R) FeII, L = PPh3, P(OMe)3, P(OPh)3 or CO

The complexes (η5-C5H5)L(RN3R′)Fe, where L = PPh3, P(OMe)3, P(OPh)3 or CO and R,R′=p-MeC6H4 orp-ClC6H4, have been prepared by reaction of suitable iron halides with Ag(RN3R′). The mechanism of formation of the Fe(RN3R′) group is thought to involve, initially, an Fe-Ag bond. The bonding mode of the triazenido ligand is chelating in a six coordinate configuration. The spectroscopic results are discussed in relation to variations in the environment of the metal atom.

Fluxional nickel(II)- and palladium (II)-triazenido (C5H5)(L)(RN3R)M complexes; Evidence for a triplet-state intermediate

The (ν5-C5H5)(L)(RN3R)Ni and (ν5-C5H5)(PPh3)(RN3R)Pd compounds, with L = PPh3, CO, CNR′, and RN3R = diaryltriazenido anion, were prepared. The bonding mode of the triazenido ligand is monodentate in the (ν5-C5H5)(PPh3)(RN3R)M phosphine compounds. The carbonyl and isonitrile groups are inserted into the nickel-nitrogen bond and a five-membered heteronuclear ring is formed in (ν5-C5-C5H5)(L)(RN3R)Ni, when L= CO and CNR′. Most compounds are fluxional, involving site exchange of the triazenidoaryl-groupsvia intermediates with a chelating bonding mode of the triazenido ligand. The (ν5-C5H5)(PPh3)(RN3R)Ni compound shows anomalous solution paramagnetism, that is correlated with the fluxional mechanism. The temperature dependence of contact shifts in the n.m.r. spectrum was determined and ΔE-values were calculated.

The molecular and crystal structure of trans-hydridobis(triphenylphosphine)(1,3-di- p-tolyltriazenido)platinum(II) [PtH(PPh 3) 2( p-CH 3C 6H 4NNNC 6H 4CH 3- p)

The structure of the title compound has been determined at room temperature from three-dimensional X-ray data collected by counter methods. The material crystallizes in the triclinic space group P 1 with two molecules in a cell of dimensions a 14.649(2), b 15.082(2), c 10.929(1) Å, α 110.99(5)°, β 102.40(5)°, γ 84.54(5)°. Full-matrix least-squares treatment of 4673 observed intensities gave an unweighted R value of 0.069. The platinum atom has square-planar coordination with PtP(1) 2.268(5), PtP(2) 2.267(5), PtN(1) 2.09(2) Å. The presence of the hydrogen atom is inferred from IR and 1H NMR data. The triazenido ligand, σ bonded to the metal through N(1), lies perpendicular to the coordination plane.

Allylic palladium(II) triazenido complexes: synthesis and spectroscopic studies

Reaction of [Pd(1-3-η-allyl)Cl] 2 with lithium triazenide (triazenide = p-XC 6H 4NN-NC 6H 4X-p; X = Cl, H, CH 3) affords dimeric complexes of the type [Pd(1-3-η-allyl)(triazenide)] 2. In the solid state the triazenido ligands are bridging two palladium atoms with their terminal nitrogen atoms, as shown by a preliminary X-ray determination of the complex with X = CH 3. The allyl groups are stereochemically equivalent. 1H NMR spectra demonstrate the presence of two conformers in solution. The major component has the same configuration found in the solid. The other conformer has stereochemically non equivalent allyl groups. The concentration ratio of the two conformers is independent of the temperature, suggesting the absence of intramolecular processes and of palladium- triazenido bond breaking. This point is discussed also by comparing the (1-3-η-allyl)(triazenide)palladium (II) dimers with the closely related(1-3-η-allyl)(acetate)palladium(II) complexes.

Conformational studies of π-allylic palladium complexes of 1,3-diphenyltriazene and 1-methyl-3-phenyltriazene

Solution isomers of dimeric allylic palladium 1,3-diphenyltriazene and 1-methyl-3-phenyltriazene complexes are identified by low temperature NMR spectroscopy. The data obtained indicate that the bridging triazenido ligands in these complexes are nonlabile and relatively inert to ligand substitution.