Yttrium Complexes Research Articles

Rare‐Earth Metal Alkyl Complexes with 3‐Arylamido‐Functionalized Indolyl Ligands: Synthesis, Characterization and Reactivity†

Summary of main observation and conclusionA series of dinuclear rare‐earth metal alkyl complexes {[μ‐η2:η1:η1‐3‐(LNCH)(CH2SiMe3)Ind]RE(CH2SiMe3)(THF)}2 (L1 = 2‐tBuC6H4, RE = Y, Gd, Dy, Er, Yb; L2 = 2,4,6‐Me3C6H2, RE = Dy, Er; Ind = indolyl) and {[μ‐η2:η1:η1‐3‐(LNCH2)Ind]RE(CH2SiMe3)(THF)}2 (L1, RE = Y, Dy, Er, Yb; L2, RE = Er, Yb) bearing 3‐arylamido functionalized indolyl ligands having diverse bonding modes with metal ions were synthesized either by the insertion reaction of the imino group to the RE—C bond or by the alkane elimination reaction. In the preparation of above complexes, rare‐earth metal alkyl complexes [μ‐η5:η1:η1‐3‐(L2NCH)(CH2SiMe3)Ind]Gd(CH2SiMe3)(THF)}2 with a μ‐η5:η1:η1 coordination mode to the gadolinium ion and {[μ‐η3:η1:η1‐3‐(L2NCH2)Ind]Dy(CH2SiMe3)(THF)}2 with a μ‐η3:η1:η1 coordination mode to the dysprosium ion were unexpectedly isolated. The reactions of 3‐(L2N=CH)Ind with Er(CH2SiMe3)3(THF)2 at room temperature, generated a tetranuclear imino‐indolyl erbium intermediate {[μ‐η1:η1‐3‐(L2N=CH)Ind]Er(CH2SiMe3)2(THF)}4, which can transform into the amido functionalized indolyl erbium complex in hot toluene. Moreover, the reactivities of the newly synthesized ytterbium complex with N‐heterocyclic compounds were investigated, affording the corresponding products of the mixed pyridyl‐indolyl, imidazolyl‐indolyl, and ortho‐metalated complexes. The yttrium complexes showed a high regioselectivity and steroselectivity for the isoprene polymerization with 1,4‐trans selectivity up to 91.7% and 1,4‐cis selectivity up to 96.1% in the presence of cocatalysts, respectively.

An Alumanylyttrium Complex with an Absorption due to a Transition from the Al-Y Bond to an Unoccupied d-Orbital.

The reaction between a dialkyl-substituted alumanyl anion and [Y(CH2 SiMe3 )2 (thf)3 ][BPh4 ] resulted in the formation of (dialkylalumanyl)yttrium complex 2, which exhibits the first 2-center-2-electron (2 c-2 e) Al-Y bond. The 1 H and 13 C NMR spectra of 2 together with an X-ray crystallographic analysis indicated a C2v symmetrical structure. DFT calculations on 2 revealed that its LUMO consists of overlapping 3 p- and 4 d-orbitals of the Al and Y atoms, respectively, and that the HOMO-LUMO gap is narrow. The UV/Vis spectrum of 2 exhibited a visible absorption at 432 nm, which suggests that the strong σ-donating and π-accepting character of the three-coordinate dialkylalumanyl ligand generates a colored d0 -complex that does not contain any π-electrons.

Luminescence of Eu3+ Ions in a Matrix of a Fluorinated Yttrium–Aluminum Composition

We studied the optical spectra of fluorinated yttrium–aluminum compositions activated by Eu3+ ions. The compositions were synthesized by thermal decomposition at 800°C of fluorine-containing complexes of yttrium, europium, and aluminum nitrate, isolated as sols from ethyl acetate (EA). The main phases of the compositions are (Y1 – xEux)OF and (Y1 – xEux)AlO3. Photoluminescence is associated with 5D1, 2 → 7F0, 1, 2 and 5D0 → 7F0, 1, 2, 3, 4 electronic transitions of 4f electrons of Eu3+ ions replacing yttrium ions in oxide and oxyfluoride. The dependences of luminescence on the composition and synthesis conditions of the compositions, the wavelength of the excitation radiation, and other factors are found.

Yttrium and lanthanide (Ln = La and Gd) complexes with cucurbit[10]uril: crystals transforming from supramolecular frameworks to coordination nanotubes

Yttrium and lanthanide complexes with cucurbit[10]uril have been investigated with crystals transforming from supramolecular structures to coordination nanotubes being revealed.

Efficient luminescence control in dithienylethene functionalized cyclen macrocyclic lanthanide complexes

We report the synthesis of an original ligand scaffold based on a dimethyl-cyclen platform Medo2pa with two dithienylethene units attached to each picolinate arm and the corresponding yttrium(iii), europium(iii) and ytterbium(iii) complexes.

Люминесценция ионов Eu-=SUP=-3+-=/SUP=- в матрице фторированной алюмоиттриевой композиции

The optical spectra of fluorinated yttrium aluminum compositions activated by Eu3+ ions were studied. The compositions were synthesized by thermal decomposition at 800 °C of fluorine-containing complexes of yttrium, europium, and aluminum nitrate, isolated as sols from ethyl acetate (EA). The main phases of the compositions are (Y1-xEux)OF and (Y1-xEux)AlO3. Photoluminescence is associated with 5D1,2 → 7F0,1,2 and 5D0 → 7F0,1,2,3,4 electronic transitions of 4f - electrons of Eu3+ ions, replacing yttrium ions in its oxide and oxyfluoride. The dependences of luminescence on the composition and synthesis conditions of the compositions, the wavelength of the exciting radiation, and other factors are established.

Bis(alkyl) scandium and yttrium complexes coordinated by an amidopyridinate ligand: synthesis, characterization and catalytic performance in isoprene polymerization, hydroelementation and carbon dioxide hydrosilylation.

New neutral bis(alkyl) Sc and Y complexes [N,Npy,N-]Ln(CH2SiMe3)2(THF)n [n = 0, Ln = Sc (1Sc), Y (1Y); n = 1, Ln = Y (1YTHF)] stabilized by a tridentate monoanionic amidopyridinate ligand were straightforwardly prepared by alkane elimination, upon mixing ligand [N,Npy,N-]H and metal precursor Ln(CH2SiMe3)3(THF)2 in toluene at 0 °C. Depending on the work-up conditions, yttrium bis(alkyl)s were isolated as either a pentacoordinate Lewis base free complex [N,Npy,N-]Y(CH2SiMe3)2 (1Y) or as a hexacoordinate THF adduct [N,Npy,N-]Y(CH2SiMe3)2THF (1YTHF). For the smaller Sc ion the only solvent-free complex [N,Npy,N-]Y(CH2SiMe3)2 (1Sc) was isolated as a pentacoordinate species irrespective of the reaction/work-up/crystallization conditions applied. Complexes 1Ln (Ln = Y, Sc) and 1YTHF were scrutinized as pre-catalysts in ternary catalytic systems Ln/borate/AliBu3 (borate = [HNMe2Ph][B(C6F5)4] or [Ph3C][B(C6F5)4]), applied to isoprene (IP) polymerization, providing moderate activity albeit high selectivity with predominant formation of 1,4-cis polyisoprene (up to 99%). The same complexes proved to be effcient catalysts also for the intermolecular hydrolelementation of styrene with various EH sustrates (pyrrolidine, morpholine, Ph2PH, PhPH2, PhSH) affording linear anti-Markovnikov addition products exclusively. After a preliminary activation by B(C6F5)3, selected bis(alkyl) complexes from this series have been finally used as valuable pre-catalysts for the CO2 hydrosylilation to CH4 in the presence of organosilanes as reducing agents (PhMe2SiH, PhSiH3, Et2MeSiH).

Lutetium and yttrium complexes supported by an anilido-oxazoline ligand for polymerization of 1,3-conjugated dienes and ε-caprolactone

Lutetium and yttrium complexes supported by an anilido-oxazoline ligand exhibit highcis-1,4 stereoselectivity for 1,3-conjugated diene polymerization and high activity for ring-opening polymerization of ε-caprolactone.

Suppressing 1H Spin Diffusion in Fast MAS Proton Detected Heteronuclear Correlation Solid-State NMR Experiments

Fast magic angle spinning (MAS) and indirect detection by high gyromagnetic ratio (γ) nuclei such as proton or fluorine are increasingly utilized to obtain 2D heteronuclear correlation (HETCOR) solid-state NMR spectra of spin-1/2 nuclei by using cross polarization (CP) for coherence transfer. However, one major drawback of CP HETCOR pulse sequences is that 1H spin diffusion during the back X→1H CP transfer step may result in relayed correlations. This problem is particularly pronounced for the indirect detection of very low-γ nuclei such as 89Y, 103Rh, 109Ag and 183W where long contact times on the order of 10–30 ms are necessary for optimal CP transfer. Here we propose two methods that eliminate relayed correlations and allow more reliable distance information to be obtained from 2D HETCOR NMR spectra. The first method uses Lee-Goldburg (LG) CP during the X→1H back-transfer step to suppress 1H spin diffusion. We determine LG conditions compatible with fast MAS frequencies (νrot) of 40–95 kHz and show that 1H spin diffusion can be efficiently suppressed at low effective radiofrequency (RF) fields (ν1,eff ≪ 0.5νrot) and also at high effective RF fields (ν1,eff ≫ 2νrot). We describe modified Hartmann-Hahn LG-CP match conditions compatible with fast MAS and suitable for indirect detection of moderate-γ nuclei such as 13C, and low-γ nuclei such as 89Y. The second method uses D-RINEPT (dipolar refocused insensitive nuclei enhanced by polarization transfer) during the X→1H back-transfer step of the HETCOR pulse sequence. The effectiveness of these methods for acquiring HETCOR spectra with reduced relayed signal intensities is demonstrated with 1H{13C} HETCOR NMR experiments on l-histidine⋅HCl⋅H2O and 1H{89Y} HETCOR NMR experiments on an organometallic yttrium complex.

Performance of Nano-3YSZ toughened β’’-Alumina solid electrolyte prepared by EDTA-Zr(IV)/Y(III) complex as surface modifier

Due to its excellent ionic conductivity and electronic insulation, β/β″-alumina is widely used as a solid electrolyte in molten salt electrochemical cell and alkali metal thermoelectric convertor (AMTEC). In this article, nano-3mol% Yttrium partial stabilized zirconia (3YSZ) toughened β″-alumina solid electrolytes (BASEs) were fabricated by surface modification of β/β’’-alumina precursor particles with ethylenediaminetetraacetic acid (EDTA) - Zirconium (IV)/Yttrium (III) complex. The performance of BASEs with 0-10 wt% amount of nano-3YSZ addition (Zr-BASE) was systematically investigated on their phase composition, density, microstructure, bending strength, and conductivity. It was found that nano-3YSZ grains were intergranular and uniformly distributed in BASE matrix even at as low as 3 wt% amount of addition, which resulted in higher density, more homogeneous microstructure, higher Weibull modulus, higher characteristic strength and increased grain boundary resistance of Zr-BASE than those of BASE without 3YSZ addition. Zr-BASE with 5 wt% amount of nano-3YSZ addition demonstrated good conductivity (0.071 S•cm−1 at 300 °C, 0.33 S cm−1 at 600 °C) and higher characteristic strength (283 MPa). The obtained results indicated that surface modification by EDTA-Zr(IV)/Y(III) complex advantaged in the preparation of better performance BASEs with a small amount of nano-3YSZ addition.

Alkyl yttrium complexes of doubly cyclometallated xanthene- and naphthalene-backbone bis(phosphinimine) ligands

The synthesis of a rigid 4,5-bis(triphenylphosphinimino)-2,7-di-tert-butyl-9,9-dimethylxanthene {(Ph3PN)2XT} ligand is outlined, along with a modified synthesis for previously reported 1,8-bis(triphenylphosphinimino)naphthalene {(Ph3PN)2NAP}. Reaction of neutral (Ph3PN)2XT with [Y(CH2SiMe3)3(THF)2] resulted in double cyclometallation, yielding the base-free monoalkyl complex, [({Ph2(C6H4)PN2XT)Y(CH2SiMe3)] (1). Layering a concentrated THF solution of 1 with hexanes at −28 °C afforded THF-coordinated [({Ph2(C6H4)PN}2XT)Y(CH2SiMe3)(THF)]·2THF (1-THF·2THF), with a distorted pentagonal bipyramidal geometry and approximately meridional coordination of the pentadentate {Ph2(C6H4)PN}2XT dianion. Similarly, (Ph3PN)2NAP reacted with [Y(CH2SiMe3)3(THF)2] to afford a THF-coordinated monoalkyl complex, [{(Ph2(C6H4)PN)2NAP}Y(CH2SiMe3)(THF)] (2-THF). Layering a DME solution of 2-THF with hexanes at −28 °C afforded X-ray quality crystals of [[{(Ph2(C6H4)PN)2NAP}Y(CH2SiMe3)(κ2-DME)]·hexane (2-DME·hexane), with a highly distorted pentagonal bipyramidal geometry and a facial coordination mode of the tetradentate {Ph2(C6H4)PN}2NAP dianion.

Dinuclear Pentacoordinated Organoyttrium Biphenolates as Initiators for the Synthesis of High-Molecular Weight Isotactic Poly(2-vinylpyridine).

Dinuclear organoyttrium biphenolato complexes have been synthesized for the first time starting from Y(CH2SiMe3)3(THF)2 and readily available biphenols with bulky substituents at the 3,3'-positions. XRD analysis revealed that these complexes are formed as homochiral dimers even though racemic biphenols were employed. Such dinuclear penta-coordinated yttrium complexes were evaluated as initiators in the polymerization of 2-vinylpyridine (2-VP). High activity and excellent isotacticity (mm > 99%) were observed. DSC analysis of poly(2-VP) showed a Tm = 221 °C, which is the highest value reported to date. Attempts to improve the low initiation efficiency of the present system were made by co-use with several organo-main-group metal reagents. Specifically, good molecular weight control within the high Mn region was achieved by the addition of Et3Al (Al/Y = 10).

Significant enhancement of catalytic properties in mononuclear yttrium complexes by nitrophenolate‐type ligands: Synthesis, structure, and catalysis for lactide polymerization

ABSTRACTThe syntheses, structures, and catalytic properties for lactones polymerization of eight novel yttrium complexes containing an amine‐bis(benzotriazole phenolate) ( C1NNBiBTP) ligand are reported. A series of nitrophenolate (NP)‐type of ligands possessing R substituents with variable electronic properties (R = NO2, Cl, H, CH3) on ortho and/or para position attached to the phenolate rings have been selected and further reacted with C1NNBiBTP‐H2 proligand and YCl3·6H2O. Two series of complexes, [Y( C1NNBiBTP)(TNP)(MeOH)2] (3), [Y( C1NNBiBTP)(2,4‐DNP)(MeOH)2] (4) and [Y( C1NNBiBTP)(2,5‐DNP)(MeOH)2] (5) with two MeOH molecules as initiators as well as [Y( C1NNBiBTP‐H)(CNP)2] (6), [Y( C1NNBiBTP‐H)(2‐NP)2] (7) and [Y( C1NNBiBTP‐H)(MNP)2] (8) with two NP derivatives, were synthesized. Their ring‐opening polymerizations of L‐lactide (L‐LA) were investigated for all complexes in order to further understand the correlations between the inductive effect of substitutions and catalytic properties. Particularly, the activity and controllability of yttrium complexes 3 and 5 were improved dramatically comparing with the literature complex with the similar coordination environment, [Y( C1NNBiBTP)(NO3)(MeOH)2], which can be a successful example to enhance the catalytic properties by exchanging coordinate molecules. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2038–2047

Ligand-Excess Yttrium Complex with a Promiscuous Ligand as a Precursor for Surface Yttrium-Alloying of Parts from Heat-Resistant Alloys

It is proposed that the potassium salt of nitrilo-tris-methylenephosphonate coordination complex with yttrium K8[YH{N(CH2PO3)3}2] · 15H2O be used as a precursor of Y-containing adsorbed layers for yttrium surface alloying via thermal or other energy impacts on a surface layer. The complex contains two crystallographically and functionally inequivalent ligand molecules. Due to the structure of the complex, the free donor centers of one of the ligand molecules are able to bond nonselectively with the metal surface and form a uniform adsorption layer even on the phase-inhomogeneous surface.

DFT studies of the electron density distribution and donor-acceptor interactions in water-soluble aminohydroximate metallamacrocyclic CaII and YIII complexes

The topology of the electron density and the nature of donor-acceptor interactions in copper-based glycinehydroximate metallamacrocycles bearing calcium(ii) and yttrium(iii) have been studied for the first time in terms of the density functional theory (DFT). The DFT calculations at the M06/Def2-TZVP level were performed taking into account non-specific (PCM) and specific solvation. Quantitative estimations of the donor-acceptor interactions and topological properties of the electron density were obtained. According to them, the thermodynamic stability of the yttrium complex is higher than that of the calcium analog. The calculated values of the Gibbs energy changes indicate the spontaneous substitution of Ca2+ by Y3+ in the metallamacrocycle in an aqueous medium.

Bidentate Sulfur Dioxide Complexes of Scandium, Yttrium, and Lanthanum Difluorides.

The SO2 complexes of scandium, yttrium, and lanthanum difluorides [MF2(O2S)] were prepared via the reactions of laser-ablated metal atoms and SO2F2 upon UV-vis irradiation in cryogenic matrixes. The presence of bidentate SO2 ligand in the products was demonstrated by the characteristic infrared absorptions as well as isotopic frequency ratios from both S18O2F2 and 34SO2F2 experiments and is further supported by DFT calculations. All three product molecules were predicted to have nonplanar C2 v symmetry with the SO2 ligand bound to the metal center through both oxygens. The computed S-O bond length and stretching frequencies of ligated SO2 approach those of SO2- as a result of electron transfer from metal center to the 1π* orbital of SO2, in agreement with the results from bonding analysis. On the basis of DFT calculations, fluorine transfer from SO2F2 to the metal center to form the MF2(O2S) complexes is highly exothermic. Although a proposed intermediate in the form of MF(O2SF) was predicted to be stable, it was not observed in the experiments, presumably because of the low energy barrier for further isomerization to MF2(O2S).

Air-stable di-nuclear yttrium complexes as versatile catalysts for lactide polymerization and copolymerization of epoxides with carbon dioxide or phthalic anhydride

Four novel di-nuclear yttrium catalysts coordinated by bis(benzotriazole iminophenolate) (BiIBTP) ligands have been synthesized and structurally characterized. The one-pot procedure of BiIBTP pro-ligand with [Y(NO3)3.6H2O] (1.0 equiv.) and 2-nitrophenol derivative (1.0 equiv.) in the presence of triethylamine (5.0 equiv.) under refluxing MeOH solution gave bimetallic yttrium nitrophenolate complexes 1–4, [(μ-BiIBTP)Y(L)]2 (BiIBTP = C13CBiIBTP or C83CBiIBTP; L = 2-nitrophenolate or 2,4-dinitrophenolate) with good to high yields. The solid-state structure of 1 and 3–4 exhibits a di-yttrium(III) di-nitrophenolate species with the pentadentate BiIBTP ligand chelating two metal atoms. Versatile catalysis towards ring-opening polymerization of cyclic ester and copolymerization of internal epoxides with carbon dioxide (CO2) or phthalic anhydride (PA) catalyzed by these di-yttrium nitrophenolate complexes was systematically studied. Experimental results revealed that air-stable complexes 3 and 4 were shown to effectively catalyze not only lactide polymerization but also copolymerization of cyclohexene oxide (CHO) with CO2 or PA. Among these compounds, di-Y complex 4 was the most active catalyst for the ring-opening polymerization of l-lactide in combination with 9-anthracenemethanol, providing poly(l-lactide)s having the expected molecular weight and narrow molecular weight distribution. Furthermore, catalyst 3 was capable of copolymerizing CO2 and CHO in the presence of co-catalysts under mild conditions, producing perfectly alternating poly(cyclohexene carbonate)s with the controllable character. In addition, the molecular weight controllable poly(PA-co-CHO)s with high ester linkage contents could be afforded on copolymerizing PA and CHO utilizing di-yttrium complex 3 as the catalyst. This work provides the facilely synthesized di-nuclear yttrium complexes as versatile catalysts for three different types of polymerization catalysis.

Living 3,4‐(Co)Polymerization of Isoprene/Myrcene and One‐Pot Synthesis of a Polyisoprene Blend Catalyzed by Binuclear Rare‐Earth Metal Amidinate Complexes

Mononuclear amidinate yttrium complex C4 H9 C(NR)2 Y(o-CH2 C6 H4 NMe2 )2 (R=2,6-iPr2 C6 H3 ) and a series of binuclear rare-earth metal complexes bearing a bridged amidinate ligand [(RN)2 C(CH2 )4 C(NR)2 ][RE{CH2 C6 H4 (o-NMe2 )}2 ]2 (R=2,6-iPr2 C6 H3 , RE=Y, Lu, Sc) were synthesized and fully characterized. The catalytic behavior of these complexes for (co)polymerization of conjugated dienes such as isoprene and myrcene in the presence of co-catalyst [Ph3 C][B(C6 F5 )4 ] was investigated. These catalytic systems show impressively high activity and 3,4-regioselectivity in living (co)polymerization. The binuclear bridged amidinate yttrium catalytic system not only exhibits the highest activity among the reported catalytic systems for 3,4-polymerization of isoprene but also allows the steady polymerization in a living manner from -20 to 80 °C. Compared with the dramatic drop of 3,4-selectivity for the mononuclear analogue, the binuclear catalytic system still shows moderate 3,4-selectivity at 80 °C. Moreover, a facile one-pot synthetic strategy for a polymer blend containing 3,4- and 1,4-polyisoprene (PIP) was established through the in situ modification of the active amidinate yttrium species by addition of an excess amount of AlMe3 .

Effect of Synthesis Conditions on the Luminescence of Europium-Containing Materials Based on Yttria and Yttrium Oxyfluorides

We have studied the luminescence of europium(III)-doped materials based on yttria and yttrium oxyfluorides. The materials were prepared through heat treatment of fluorine-containing yttrium and europium(III) thioacetamide complexes at temperatures of 400, 600, and 800°C for 2 to 6 h. The products were shown to consist of (EuхY1 –х)F3, (EuхY1 –х)5O4F7, (EuхY1 –х)OF, and (EuхY1 –х)2O3 phases. We have proposed a scheme that reflects the formation sequence of the main components of the materials in the above temperature range. Narrow-band luminescence of the materials has been shown to arise from Eu3+5D0 → 7Fj electronic transitions. The origin of the observed broad luminescence band peaking in the range 480–500 nm can be understood in terms of surface structural defects, the particle size, and the broad particle size distribution. The luminescence spectrum has been shown to be influenced by the starting-mixture composition, synthesis conditions, host composition, and excitation wavelength. Some of the observed luminescence features have been shown to be due to the effect of S2– ions in the composition of europium-containing activator centers.

Synthesis of well-defined yttrium-based Lewis acids by capturing a reaction intermediate and catalytic application for cycloaddition of CO2 to epoxides under atmospheric pressure

Single-site yttrium complexes were prepared by immobilization of an intermediate of cycloaddition of CO2 to epoxides and applied in catalysis.