Neutral Yttrium Research Articles

Reactivity of a Neutral Yttrium(III) Trimethyl Complex toward Brønsted and Lewis Acids.

The present study corroborates that the neutral tridentate N-ligand 1,4,7-trimethyl-triazacyclononane (Me3TACN) qualifies as a versatile platform to study selective ligand exchange with rare-earth-metal alkyl complexes, herein [(Me3TACN)YMe3]. Treatment with Brønsted-acidic bis(dimethylsilyl)amine, HN(SiHMe2)2, gave selectively the mono-exchanged heteroleptic complex [(Me3TACN)YMe2{N(SiHMe2)2}]. Depending on the molecular ratio employed, the reaction of [(Me3TACN)YMe3] with AlMe3 resulted in the isolation/crystallization of [(Me3TACN)YMe2(AlMe4)] [1 : 1] or ion-separated [(Me3TACN)YMe(AlMe4)][AlMe4] [1 : 2] and [(Me3TACN)YMe(AlMe4)][Al2Me7] [1 : 3]. Analogous reactions with the heavier group 13 methyls GaMe3 and InMe3 generated mixed methyl/tetramethylgallato complex [(Me3TACN)YMe2(GaMe4)] and ion-separated [{(Me3TACN)YMe2}2{μ-Me}][InMe4]. Finally, dimethylalane, HAlMe2, converted [(Me3TACN)YMe3] into heteroaluminate [(Me3TACN)Y(HAlMe3)3], representing an AlMe3-supported, molecular yttrium trihydride complex. All compounds were investigated by single crystal X-ray diffraction (SC-XRD), homo- and heteronuclear (13C, 27Al, 89Y, 115In) NMR as well as IR spectroscopies and elemental analyses.

A rare isocyanide derived from an unprecedented neutral yttrium(ii) bis(amide) complex.

A room temperature stable complex formulated as Y(NHAr*)2 has been prepared, where Ar* = 2,6-(2,4,6-(iPr)3C6H2)C6H3, by KC8 reduction of ClY(NHAr*)2. Based on EPR evidence, Y(NHAr*)2 is an example of a d1 Y(ii) complex with significant delocalization of the unpaired electron density from the metal to the ligand. The isolation of molecular divalent metal complexes is challenging for rare earth elements such as yttrium. In fact, stabilization of the divalent state requires judicious ligand design that allows the metal center to be coordinatively saturated. Divalent rare earth elements tend to be reactive towards various substrates. Interestingly, Y(NHAr*)2 reacts as a radical donor towards t BuNC to generate an unusual yttrium isocyanide complex, CNY(NHAr*)2, based on spectroscopic evidence and single-crystal X-ray diffraction data.

Experimental radiative lifetimes, branching fractions, and oscillator strengths of some levels in Y I

We measure the radiative lifetimes of 17 levels in Y I with a time-resolved laser-induced fluorescence technique. Of these 17 levels, 13 are reported on for the first time to the best of our knowledge. Branching fractions for 72 lines related to these Y I levels are determined based on the spectra by the Fourier transform spectrometer at the National Solar Observatory (NSO) on Kitt Peak, USA (http://diglib.nso.edu/ftp.html). By combining the results of lifetimes and branching ratios, the transition probabilities (gA) and oscillator strengths (log(gf)) of these lines are determined. The radiative parameter results obtained in the present work well enrich the atomic database of neutral yttrium, including the experimental values of 62 lifetimes and the gA and log(gf)) of 438 transitions.

Synthesis, characterization, and styrene polymerization performance of organo yttrium complexes supported by imino-fuctionalized indenyl ligand

ABSTRACTAmine elimination of Y[N(SiHMe2)2]3(THF)2 with the imino-functionalized indenyl ligand C9H7CH2CH = N-2,6-iPr2C6H3 in 1:1 and 1:2 molar ratio afforded the mono-indenyl-ligated yttrium bis(silylamide) complex (C9H6CH2CH = N-2,6-iPr2C6H3)Y[N(SiHMe2)2]2 (4) and the neutral yttrium complex (C9H6CH2CH = N-2,6-iPr2C6H3)(C9H6CH = CH-N-2,6-iPr2C6H3)Y (5), respectively. Both complexes were characterized by elemental analysis and NMR. X-ray single crystal structural diffraction showed that the central metal in 5 is four-coordinated by two indenyl ligands and two nitrogen atoms in η5/κ1-mode, if the indenyl ring is regarded as occupying an independent vertex. In the presence of AliBu3 and activated by one equimolar amount of [Ph3C][B(C6F5)4], complex 4 showed activity toward syndiospecific polymerization of styrene.

DFT calculations on polarizabilities and hyperpolarizabilities for the neutral and anionic yttrium oxide clusters

The electronic properties, polarizabilities, first and second hyperpolarizabilities of YOn clusters of [Formula: see text]–12 were studied using the quantum chemical method. The vertical ionization potential (VIP) values for the anionic clusters increase monotonically with the cluster size. Among the neutral clusters YO3 and YO8 have the least chemical hardness values, where in anionic clusters with size [Formula: see text] possesses the least chemical hardness. Anionic clusters have more electrons attracting tendency than the neutral clusters. The computed static mean polarizability of neutral yttrium oxides has positive values but is close to zero. The incorporation of oxygen atom quenches the polarizability of yttrium. The computed polarizability anisotropy of neutral clusters shows an oscillatory effect both at static and at dynamic conditions. The first hyperpolarizability for many YOn clusters are close to zero. The existence of high symmetry in these clusters reduces the first hyperpolarizability values which was supported by the small dipole moments. The computed [Formula: see text] values for the static neutral and anionic clusters show only a small variation. The decrease in the polarizability and second hyperpolarizability with size can be interpreted in terms of the electronic delocalization and chemical bonding in the clusters.

Radiative lifetimes, branching fractions, transition probabilities and oscillator strengths of some levels for neutral yttrium

The radiative lifetime measurements using the time-resolved laser-induced fluorescence (TR-LIF) technique are reported for 34 levels of Y I between 27 824.50 and 50 254.0 cm−1, among which 27 lifetimes are reported for the first time. The branching fraction (BF) measurements based on the emission spectrum of a hollow cathode lamp (HCL) were performed for 12 of these levels, and the results of 64 lines between 274.250 and 670.063 nm were obtained. By combining them with lifetime values, the transition probabilities and absolute oscillator strengths of these lines were determined. The lifetime and oscillator strength results are in general good agreement with the data by Hannaford et al (Hannaford et al 1982 ApJ 261 736).

Half-sandwich rare-earth metal tris(alkyl) ate complexes catalyzed phosphaguanylation reaction of phosphines with carbodiimides: an efficient synthesis of phosphaguanidines

Half-sandwich Y/Li ate complex displays better catalytic activity for phosphaguanylation reaction of phosphines with carbodiimides than the neutral yttrium complexes.

Synthesis and Characterization of Amine-Bridged Bis(phenolate) Yttrium Guanidinates and Their Application in the Ring-Opening Polymerization of 1,4-Dioxan-2-one

A series of neutral yttrium guanidinates supported by an amine-bridged bis(phenolate) ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of 1,4-dioxan-2-one (p-dioxanone, PDO) were explored. Metathesis reactions of amine-bridged bis(phenolate) yttrium chlorides LLnCl(THF) [L = Me2NCH2CH2N{CH2-(2-OC6H2-tBu2-3,5)}2] with corresponding lithium guanidinates generated in situ in a 1:1 molar ratio in THF gave the neutral yttrium guanidinates LY[R2NC(NR1)2] [R1 = −Cy, R2N = −N(TMS)2 (1), −NiPr2 (2), −N(CH2)5 (3); R1 = −iPr, R2N = −NiPr2 (4) −NPh2 (5))]. These complexes were well characterized by elemental analyses, IR, and NMR spectroscopy. The definitive molecular structures of these complexes were determined by single-crystal X-ray analysis. It was found that these complexes can efficiently initiate the ring-opening polymerization (ROP) of PDO, and the catalytic activity is affected by the nature of the guanidinate groups with the active sequence of 1 > 2 ≈ 3 ≈ 4 > 5. The influences of reaction conditions such as polymerization time, polymerization temperature, and molar ratio of monomer to initiator on the polymerization were also investigated. The polymerization kinetics of PDO catalyzed by complex 1 is first-order with respect to monomer concentration, and the apparent activation energy amounts to 30.8 kJ mol–1. The mechanistic investigations showed that the ROP of PDO proceeded through a coordination–insertion mechanism with a rupture of the acyl–oxygen bond of the monomer. MALDI-TOF mass spectrum analysis of the oligomer revealed that there are two kinds of polymer chains in this catalytic system, e.g., the linear chains H–[OCH2CH2OCH2CO]n–OH and the PPDO macrocycles.

Synthesis, Characterization, and Activity of Yttrium(III) Nitrate Complexes Bearing Tripodal Phosphine Oxide and Mixed Phosphine–Phosphine Oxide Ligands

A series of four tripodal phosphine oxide ligands, (OPR(2))(2)CHCH(2)POR(2) (1a-1d), and four mixed phosphine-phosphine oxide ligands, (OPR(2))(2)CHCH(2)PR(2) (3a-3d), were synthesized and coordinated to yttrium to produce Y(NO(3))(3)[(OPR(2))(2)CHCH(2)POR(2)] (2a-2d) and Y(NO(3))(3)[(OPR(2))(2)CHCH(2)PR(2)](OPPh(3)) (4a-4d) complexes. The previously reported ligand 1a and unknown phosphine oxide ligands 1b-1d were generated in an unprecedented trisubstitution reaction of bromoacetaldehyde diethyl acetal, while the novel partially reduced ligands 3a-3d were synthesized from 1a-1d according to a known literature protocol for the selective monoreduction of bisphosphine oxides. The neutral yttrium complexes 2a-2d are nine-coordinate and display a tricapped trigonal-prismatic geometry. Complexes 4a-4d are also neutral, nine-coordinate species and have a pendant phosphine functionality, which provides the potential to form bimetallic early-late transition-metal complexes. Additionally, yttrium complexes 2a-2d were activated with base and tested for the ring-opening polymerization of ε-caprolactone, but the results showed that base by itself was significantly more effective than the yttrium species investigated.

Electronic State Distributions of YBa2Cu3O7-x Laser-Ablated Plumes

A systematic study of the spectrally resolved atomic emission arising from the laser ablation of YBa(2)Cu(3)O(7-x) targets in the presence of an oxygen background reveals statistically distributed populations with characteristic temporally averaged electronic temperatures of 0.28-0.38 eV, 0.28-0.37 eV, and 0.40-0.48 eV for neutral barium, yttrium, and copper, respectively. The higher electronic temperatures of the lighter copper atoms cannot be explained by the effects of temporal averaging, as the time-of-flight spectra are similar for all three atomic species. The electronic temperatures decline slowly with distance from the target, with a characteristic length of 20 to 200 mean free paths. The plume kinetic energies determined from gated imagery recorded time-of-flight spectra are much higher, 3-250 eV, suggesting a small fraction of the kinetic energy is converted to electronic excitation during each collision at the shock contact front. A correlation between electronic temperatures and shock strength reduces the dimensionality of the dependence on pressure and target distance. The dependence of electronic temperature on deposition condition is weak, suggesting the electronic state distribution is a poor candidate as a monitor for process control during the manufacture of coated conductors.

Reactions of Imidazoles with Electrophilic Metal Alkyl Complexes

The C−C coupling of two molecules of 1-methylbenzimidazole was effected by neutral yttrium and lutetium benzyl complexes supported by a 1,1′-ferrocenylene-diamide ligand. This transformation involves the C−H activation and coupling of one η2(N,C)-imidazolyl fragment with a coordinated 1-methylbenzimidazole ligand. The coupled product can be transformed into a mono- or dinuclear product, in which one of the imidazole rings is cleaved. Variable-temperature 1H and 2H NMR spectroscopic data support the reversibility of the C−C coupling event and explain the formation of the dinuclear product.

Chiral Amido Alkyl Rare Earth Complexes: A New Family of Asymmetric Intramolecular Hydroamination Catalysts

New chiral binaphthylamido alkyl ate and neutral yttrium and ytterbium complexes have been synthesized and characterized. X-ray structures have been obtained for ate alkyl complexes [(R)-C20H12(NC5H9)2]Y[(μ-Me)2Li(THF)2(μ-Me)Li(THF)] and [(R)-C20H12(NC5H9)2]Ln[(μ-Me)2Li(TMEDA)(μ-Me)Li(OEt2)] (Ln = Y, Yb) and for the neutral complex [(R)-C20H12(NC5H9)2]YCH2SiMe3(DME). Both types of complexes can be easily prepared in a one-pot procedure starting from yttrium and ytterbium chlorides and used in situ. They proved to be very efficient catalysts for enantioselective intramolecular hydroamination of aminopentenes or aminohexene at room temperature with enantiomeric excesses up to 83%.

Neutral Yttrium Tris(amide) and Ate Complexes Coordinated by an (R)‐N,N′‐Diisopropyl‐1,1′‐binaphthyl‐2,2′‐diamido Ligand as Enantioselective Catalysts for Intramolecular Hydroamination

AbstractA bis(amido)yttrium chloride coordinated by (R)‐N,N′‐diisopropyl‐1,1′‐binaphthyl‐2,2′‐diamide [Y{(R)‐C20H12(NiPr)2}Cl(thf)2] has been prepared and characterized by X‐ray analysis along with the corresponding yttrium ate complex [Li(thf)4][Y{(R)‐C20H12(NiPr)2}2]. The reaction of [(R)‐N,N′‐diisopropyl‐1,1′‐binaphthyl‐2,2′‐diamido]yttrium chloride with lithium diisopropylamine leads to the formation of a neutral tris(amido)yttrium complex which was characterized by NMR spectroscopy. The new complexes [Y{(R)‐C20H12(NiPr)2}{NiPr2}] and [{Li(thf)4}(Y{(R)‐C20H12(NiPr)2}2)], which contain the same enantiopure binaphthyldiamido ligand, are compared for the catalysis of several intramolecular hydroamination reactions. Both complexes provide pyrrolidines andpiperidines with moderate to high enantioselectivities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Competition between C−C and C−H Activation in Reactions of Neutral Yttrium Atoms with Four Butene Isomers

The reactions of neutral, ground-state Y (a2D, s2d1) with 1-butene, cis-2-butene, trans-2-butene, and isobutene were studied using crossed molecular beams. At a collision energy of 26.6 kcal/mol, four processes were observed for reactions with cis- and trans-2-butene and 1-butene, corresponding to nonreactive scattering of yttrium atoms and formation of YC4H6 + H2, YH2 + C4H6, and YCH2 + C3H6. For the isobutene reaction, all channels but the YH2 product channel were observed. Experimentally measured product branching ratios indicate that YC4H6 formation is always the dominant process. However, for cis- and trans-2-butene and 1-butene, YH2 formation is significant. Formation of YCH2 was minor for all four isomers. At a collision energy of 11.0 kcal/mol, only YC4H6 + H2 and nonreactive scattering were observed for all four butene isomers. A common mechanism is proposed for reactions of Y with all four isomers, involving formation of a π-complex, followed by insertion of Y into a methyl C−H bond producing a ...

Competition between C−C and C−H Activation in Reactions of Neutral Yttrium Atoms with Cyclopropane and Propene

Branching ratios between C−C and C−H bond activation were measured for reactions of ground-state Y (a2D, s2d1) atoms with two C3H6 isomers (cyclopropane and propene) in crossed molecular beams. For both isomers, C−C bond activation led to formation of YCH2 + C2H4, whereas C−H activation led to YC3H4 + H2 and YH2 + C3H4. The angular and velocity distributions for all three product channels and for nonreactive collisions were measured at several collision energies (Ecoll). For Y + cyclopropane, the branching ratio for YCH2 + C2H4 increased relative to YC3H4 + H2 with increasing Ecoll, this C−C activation channel becoming dominant at Ecoll ≥ 19 kcal/mol. For the propene reaction, φYCH2/φYC3H4 also increased with Ecoll, reaching 0.75:1.00 at Ecoll = 28.8 kcal/mol. For both C3H6 reactants, formation of YH2 + C3H4 was observed as a minor channel at the highest collision energies. Experimental results and Rice−Ramsperger−Kassel−Marcus (RRKM) modeling indicate that for propene reactions all three channels involve initial formation of π-association complexes that undergo insertion into one of the sp3-hybridized β-C−H bonds in the methyl substituent. Decay of the yttrium allyl hydride intermediate by β-H migration leads to the two C−H activation products, YC3H4 + H2 and YH2 + C3H4. We propose that the YCH2 + C2H4 channel involves reverse β-H migration forming the same strongly bound metallacyclobutane intermediate formed in the Y + cyclopropane reaction.

Strontium-90 determination in biological and environmental samples by direct milking of its daughter product, yttrium-90

A method is presented for the determination of 90Sr in environmental samples by direct milking of 90Y. Pyridine-2,6-dicarboxylic acid forms an anionic complex with yttrium which is retained on an anionic resin. Most of the matrix elements are washed out of the column as neutral or uncomplexed species and yttrium is eluted by increasing the ionic force of the eluent solution. This method gives yttrium recoveries between 65% to 85% for soil, grass, milk and bone samples with very high radiochemical purity (90Y average half-life of 66±4 hours) and a detection limit of 0.3 Bq/kg of soil. The method supports a calcium content up to 3 g per sample without any decrease in yttrium yield, allowing the measurement of milk, milk-teeth and bone samples with no concentration step in one day.

Photoelectron Spectroscopy of Yttrium Oxide Cluster Anions: Effects of Oxygen and Metal Atom Addition

The photoelectron spectra of small gas-phase YnOm- clusters (n = 2−10, m = 1−3) are measured at photon energies of 3.49 and 4.66 eV. Cluster generation is performed with the aid of laser vaporization, whereas the kinetic energy of electrons is measured using a magnetic bottle photoelectron spectrometer. The evolution of the electronic structure of neutral yttrium oxide clusters is discussed in terms of both sequential oxygen addition to the metal cluster core and sequential metal atom increase. Electron affinities and vertical detachment energies are measured and compared to ionization potentials of the monoxide cluster series [Knickelbein, M. J. Chem. Phys. 1995, 102, 1]. A general trend in the observed photoelectron spectra is a shifting of threshold energies to higher binding energies with increasing cluster size n. At low electron binding energies, main spectral features are contributed from metal d-band orbitals whereas the O 2p contribution becomes apparent with increasing oxygen content due to a hi...

A study of the formation of acid and neutral yttrium oxalate powders from precipitation-stripping reaction in a Lewis-type cell

In a previous paper, a kinetic study of the precipitation stripping of yttrium oxalate powders from yttrium-loaded HDEHP solution was conducted using a Lewis-type cell. The variation in yttrium content in organic phase versus time with a constant liquid-liquid interfacial area allowed the determination of the initial precipitation stripping rate. The work reported here has used these experimental results and observations to investigate mechanisms for the precipitation of YH(C 2O 4) 2 · 3H 2O(s) and Y 2(C 2O 4) 3 · 10H 2O(s) salts. The precipitation of the acid salt is assumed to be based on a fast nucleation step followed by a continuous growth process. The rate-controlling step is the displacement of organic dimers H 2L 2 from the intermediate complex Y(HL 2) 2 + adsorbed onto a free site of the salt located at the liquid-liquid interface by oxalic acid. The precipitation of the neutral salt can be analysed by a model based on nucleation and agglomeration, assuming that there is negligible growth. In the mechanism considered the rate-controlling step is the first step of the stripping reaction of yttrium.

Powder Diffraction Studies in the YONO3-Y2O3 System

The crystal structure of yttrium oxide nitrate and the microstructure of the oxide obtained from its thermal decomposition have been investigated by modern powder diffraction methods. Sequential high-temperature diffraction studies of the thermal decomposition of two precursors of yttrium oxide nitrate, i.e., neutral yttrium nitrate and yttrium hydroxide nitrate, are reported. The structure of YONO3 has been determined ab initio from conventional powder diffractometry using monochromatic X-rays. The pattern was indexed by the successive dichotomy method yielding tetragonal unit cell dimensions: a = 3.8590(1) Å and c = 9.7161(6) Å. The space group is P4/nmm and Z = 2. Most of the atoms were located by direct methods and the remaining ones from a Fourier map. Refinement of the complete diffraction profile parameters converged to final agreement factors Rp = 0.12, Rwp = 0.16 and RF = 0.039. The structure is closely related to the matlockite PbFCl-type structure. The microstructure of ex-oxide-nitrate yttrium oxide has been analysed by total pattern fitting techniques, from which strain-free coherently diffracting nanodomains with a rectangular parallelepipedic shape have been obtained.

Photoionization cross section and resonance structure of atomic yttrium.

Many-body perturbation theory has been used to calculate the photoionization cross section of neutral yttrium from threshold at 6.52--100.0 eV. The resonance structure due to 4p excitations to 4d states has also been calculated. Hartree-Fock results are also presented for comparison.