José M. Carretas

Gas-phase reactivity of rare earth cations with phenol: competitive activation of C–O, O–H, and C–H bonds

The gas-phase reactions of Sc+, Y+, and Ln+ (Ln=La-Lu, except Pm) ions with phenol were studied by Fourier transform ion cyclotron resonance mass spectrometry. All the ions except Yb+ were observed to react with the organic substrate, activating O-H, C-O, and/or C-H bonds, with formation of MO+, MOH+, and/or MOC6H4+ ions as primary products. The product distributions and the reaction efficiencies obtained showed the existence of important differences in the relative reactivity of the rare earth metal cations, which are discussed in terms of factors like the electron configurations of the metal ions, their oxophilicity, and the second ionization energies of the metals. The primary product ions participated in subsequent reactions, yielding species such as M(OH)(OC6H5)+, which lead mainly to M(OC6H5)2(HOC6H5)n+ ions, where n=0–2. Formation of M(OC6H5)(HOC6H5)n+ species was also observed in the case of the metals that have high stabilities of the formal oxidation state 2+, Sm and Eu.

Experimental aspects of metal vapour synthesis of alkoxides and aryloxides of lanthanides

Abstract The synthesis of metal alkoxides and aryloxides of lanthanides by the metal vapour technique has been investigated. The reactions of Ce, Sm, Eu and Yb with MeOH, EtOH and PriOH were studied. The compound Sm[OC6H3(But)2]3 was obtained from the reaction of samarium with 2,6-di-t-butylphenol.

Gas phase reactivity of rare earth metal cations with trialkylorthoformates: synthesis of neutral rare earth alkoxides

Abstract Gas phase reactions of the rare earth metal cations Y + and Ln + (Ln = La–Lu, except Pm) with trimethylorthoformate and of Y + and Lu + with triethyl and tripropyl orthoformates were studied by Fourier transform ion cyclotron resonance mass spectrometry. The results obtained were compared with previous observations made with the remaining rare earth cation Sc + and confirmed that, in the gas phase, trialkylorthoformates can be good alkoxy group suppliers, leading to dialkoxymetal ions, which subsequently react with the orthoesters to form a dialkoxymethyl cation and, presumably, a neutral metal trialkoxide. These reactions appear to be a possible route for the gas phase synthesis of rare earth metal alkoxides.

Synthesis and characterization of polynuclear lanthanide aryloxides

The reactions of europium and ytterbium in liquid ammonia with a solution of 1-naphthol in tetrahydrofuran provide a convenient route to lanthanide aryloxides. The polymetallic lanthanide complexes [Eu 4 (μ-OC 10 H 7 ) 6 (OC 10 H 7 ) 2 (THF) 10 ].2THF 1 and [Yb(μ-OC 10 H 7 )-(OC 10 H 7 ) 2 (THF)(MeCN)] 2 .2MeCN 2 were synthesized and characterized by X-ray diffraction studies.

Gas-Phase Reactions of Molecular Oxygen with Uranyl(V) Anionic Complexes—Synthesis and Characterization of New Superoxides of Uranyl(VI)

Gas-phase complexes of uranyl(V) ligated to anions X(-) (X = F, Cl, Br, I, OH, NO3, ClO4, HCO2, CH3CO2, CF3CO2, CH3COS, NCS, N3), [UO2X2](-), were produced by electrospray ionization and reacted with O2 in a quadrupole ion trap mass spectrometer to form uranyl(VI) anionic complexes, [UO2X2(O2)](-), comprising a superoxo ligand. The comparative rates for the oxidation reactions were measured, ranging from relatively fast [UO2(OH)2](-) to slow [UO2I2](-). The reaction rates of [UO2X2](-) ions containing polyatomic ligands were significantly faster than those containing the monatomic halogens, which can be attributed to the greater number of vibrational degrees of freedom in the polyatomic ligands to dissipate the energy of the initial O2-association complexes. The effect of the basicity of the X(-) ligands was also apparent in the relative rates for O2 addition, with a general correlation between increasing ligand basicity and O2-addition efficiency for polyatomic ligands. Collision-induced dissociation of the superoxo complexes showed in all cases loss of O2 to form the [UO2X2](-) anions, indicating weaker binding of the O2(-) ligand compared to the X(-) ligands. Density functional theory computations of the structures and energetics of selected species are in accord with the experimental observations.

Europium(II) and ytterbium(II) aryloxide chemistry: synthesis and crystal structure of [Eu(OC6H3But2-2,6)2(THF)3]·0.75C7H8 and [Yb(OC6H3But2-2,6)2(NCMe)4]

Abstract The reactions of europium and ytterbium with 2,6-di-tert-butylphenol were studied by the metal vapour synthesis technique and by dissolution in liquid ammonia. The lanthanide complexes [Eu(OC6H3But2-2,6)2(THF)3]·0.75C7H8 1 and [Yb(OC6H3But2-2,6)2(NCMe)4] 2 were synthesized and characterized by X-ray diffraction studies.

Oxidation of Actinyl(V) Complexes by the Addition of Nitrogen Dioxide Is Revealed via the Replacement of Acetate by Nitrite.

The gas-phase complexes AnO2(CH3CO2)2(-) are actinyl(V) cores, An(V)O2(+) (An = U, Np, Pu), coordinated by two acetate anion ligands. Whereas the addition of O2 to U(V)O2(CH3CO2)2(-) exothermically produces the superoxide complex U(VI)O2(O2)(CH3CO2)2(-), this oxidation does not occur for Np(V)O2(CH3CO2)2(-) or Pu(V)O2(CH3CO2)2(-) because of the higher reduction potentials for Np(V) and Pu(V). It is demonstrated that NO2 is a more effective electron-withdrawing oxidant than O2, with the result that all three An(V)O2(CH3CO2)2(-) exothermically react with NO2 to form nitrite complexes, An(VI)O2(CH3CO2)2(NO2)(-). The assignment of the NO2(-) anion ligand in these complexes, resulting in oxidation from An(V) to An(VI), is substantiated by the replacement of the acetate ligands in AnO2(CH3CO2)2(NO2)(-) and AnO2(CH3CO2)3(-) by nitrites, to produce the tris(nitrite) complexes AnO2(NO2)3(-). The key chemistry of oxidation of An(V) to An(VI) by the addition of neutral NO2 is established by the substitution of acetate by nitrite. The replacement of acetate ligands by NO2(-) is attributed to a metathesis reaction with nitrous acid to produce acetic acid and nitrite.

Dépôt chimique en phase vapeur à basse température de revêtements dans le système V-C-N à partir de bis(arene)vanadium

Vanadium carbide coatings V8C7 have been deposited on steel substrates by MOCVD using bis(arene)vanadiums as precursors at temperatures lower than 550 °C. Addition of C6Cl6 in the gas phase allows to reduce the carbon content of the films to 13 at. %. These metal coatings exhibit the features of a metastable carbon-rich solid solution. Carbonitride V(C,N) and nitride δ-VN layers with only 5 at. % carbon have been deposited in the presence of NH3. These reactive gas phases allow to grow almost all the phases of the V-C-N ternary diagram.

Crystal structure of bis[1-{(3,5-dimethyl-1H-pyrazol-1-yl)methyl}-3,5-dimethyl-1H-pyrazol-2-ium] hexachlorouranate(IV): [H2C(3,5-Me2pz)(3,5-Me2pzH)]2[UCl6]

The X-ray diffraction study of a single crystal with the composition [H2C(3,5-Me2pz)(3,5-Me2pzH)]2[UCl6] (1) is performed. This compound is the product of an attempted synthesis of a bis(pyrazolyl)methane complex of uranium(IV) obtained by the reaction of UCl4 with bis(3,5-dimethylpyrazol-1-yl)methane in THF. 1 crystallizes in the space group P-1 of the triclinic system: a = 9.6616(2) Å, b = 9.6946(2) Å, c = 10.7314(2) Å, α = 107.6210(10)°, β = 115.5600(10)°, γ = 99.6710(10)°, V = 810.45(3) Å3, Z = 1, dcalc = 1.765 g/cm3, μ = 5.528 mm−1, R1 = 0.0249. The structural unit consists of two separated [H2C(3,5-Me2pz)(3,5-Me2pzH)]+ cations and a UCl62− anion. In the solid state structure of 1 several short intermolecular N-H⋯N and C-H⋯Cl contacts are identified suggesting the presence of hydrogen bonds.