Synergistic extraction of Ce(III), Eu(III) and Tm(III) with a mixture of picrolonic acid and benzo-15-crown-5 in chloroform

Summary The synergistic mixture comprising picrolonic acid (HPA) and benzo-15-crown-5 (B15C5) in chloroform has been used for the extraction of Ce(III), Eu(III) and Tm(III) as representatives of lanthanide(III) ions from pH 1-2 solutions having ionic strength of 0.1 mol^. dm^-3(K⁺/H⁺, Cl^-). The composition of the extracted species has been determined as M(PA)₃^. nB15C5 where M is Ce, Eu and Tm and n=1 or 2. The influence of various anions and cations on the extraction of these ions has also been studied and only oxalate, cyanide and tartrate have some deleterious effect. The extraction equilibrium constants have been evaluated and discussed.     

Structural and selectivity of 18-crown-6 ligand in lanthanide-picrate complexes

The selectivity factor in the separation of lanthanide could be associated with the coordination behaviour. Thus, we observed the study in the solid phase to understand the coordination pattern of Ln(III) with the 18-crown-6 (18C6) ligand. Good selectivity of the rigid 18C6 ligand toward Ln(III) depends on gradually smaller their ionic radii of Ln(III) in the complexes formation in the presence of picrate anion (Pic⁻), i.e. lanthanide contraction and steric effects as clearly shown in the series of [Ln(Pic)₂(18C6)]⁺(Pic)⁻ {Ln = La, Ce, Pr, Nd, Sm, Gd} and [Ln(Pic)₃(OH₂)₃] · 2(18C6) · 4H₂O {Ln = Tb, Ho} complexes. The La-Gd complexes crystallized in an orthorhombic with space group Pbca, while the Ho complex crystallized in triclinic with space group . The lighter lanthanides complexes [La-Sm] had a 10-coordination number from the 18C6 ligand and the two picrates, forming a bicapped square-antiprismatic geometry. Meanwhile, the middle lanthanide complex [Gd] had a nine-coordination number from the 18C6 ligand and the two picrates, forming a tricapped trigonal prismatic geometry. The heavier lanthanide [Ho] is rather unique, since Ho(III) coordinated with nine oxygen atoms from three picrates and three water molecules in the opposite direction whereas three 18C6 molecules surrounded in the inner coordination sphere, forming a trigonal tricapped prismatic geometry. The 18C6 ligand is effective in controlling the molecular geometry and coordination bonding of Ln-O and can use a crystal engineering approach. No dissociation of Ln-O bonds in solution was observed in NMR studies conducted at different temperatures. The photoluminescence spectrum of the Pr complex has typical 4f-4f emission transitions, i.e. ³P₀ → ³F₂ (650 nm), ¹D₂ → ³F₂ (830 nm) and ¹D₂ → ³F₄ (950 nm).     

Synergic extraction of trivalent gadolinium,europium and americium radionuclides by 15-crown-5 or 18-crown-6 mixed with thenoyltrifluoroacetone from perchlorate medium

Synergic extraction of trivalent Eu, Gd and Am from aqueous perchlorate medium has been studied using mixtures of thenoyltrifluoroacetone (HTTA) and 15-crown-5 or 18-crown-6 (CE) in chloroform at (25±1) °C. Slope analysis of the extraction results indicated a general formula of M(TTA)₃·(CE)₂ for the extracted species. The stability order took the sequence Eu(TTA)₃·(CE)₂>Am(TTA)₃)·(CE)_2>>Gd(TTA)₃·(CE)₂ with 15C5 and Am(TTA)₃·(CE)₂>Eu(TTA)₃·(CE)₂>Gd(TTA)₃·(CE)₂ with 18C6. The synergic factors, extracton constants and formation constants of the extracted species were determined and discussed in terms of the correspondence between cavity size of the crown ethers and ionic crystal radii.     

Complexes of Lanthanoid Nitrates with 15-Crown-5 and 18-Crown-6 Ethers

Complexes between the heavier lanthanoid nitrates Ln(NO₃)₃ and 15-crown-5 ( 1 ) and 18-crown-6 ( 2 ) ethers were isolated and characterized. Both 1:1 and 4:3 complexes are formed with each Ln(III) ion, except in the case of Gd and 2 . The thermal transformation of the 1:1 complexes into the corresponding 4:3 complexes was studied by thermogravimetry and by DSC, X-ray and vibrational data provide information about the structure of these complexes. The interaction between Ln(III) ions and ligands 1 and 2 in non-aqueous solutions is discussed on the basis of conductometric, fluorescence, UV./VIS. and ¹H-NMR. data. Only 1:1 complexes of 2 formed in solution and their formation constants range from logK_f = 4.4 (Ln = La) to 2.4 (Ln = Yb); for Eu, K_f of the 15-crown-5 and 18-crown-6 ether complexes are of the same order of magnitude. For La, Pr, Nd, Eu, Yb, a variable temperature NMR. study gave some indications about the chemical exchanges in solution. The factors which determine the stoichiometry of the complexes are discussed.     

Synthesis and structure of heteroleptic triple-decker neodymium,europium, holmium,erbium, and ytterbium crown phthalocyaninates

Two series of heteroleptic crown-substituted tris(phthalocyaninate) complexes (Pc)Ln[(15C5)₄Pc]Ln(Pc) and [(15C5)₄Pc]Ln[(15C5)₄Pc]Ln(Pc), where 15C5 is 15-crown-5, (Pc²⁻) is the phthalocyaninate dianion, Ln = Nd, Eu, Ho, Er, and Yb, were prepared by the reaction of tetra-15-crown-5-phthalocyanine H₂[(15C5)₄Pc] with the corresponding lanthanide acetylacetonates and lanthanum bis(phthalocyaninate) La(Pc)₂, which was used as a phthalocyaninate dianion donor. The composition and structure of the synthesized complexes were confirmed by MALDI TOF mass spectrometry, UV-Vis absorption spectroscopy, and ¹H NMR. Complete assignment of the proton resonance signals of the paramagnetic lanthanide complexes was based on analysis of lanthanide-induced shifts.     

Solvent extraction of lanthanoid/III/ with 18-crown-6 from aqueous trichloroacetate solutions to 1,2-dichloroethane

Extraction behaviour of lanthanoid/III/ has been investigated by using 18-crown-6/CR/ as a neutral microcyclic ligand, trichloroacetate/TCA^–/ as an anionic counter ion, and 1,2-dichloroethane as an organic solvent. From the equilibrium studies, the extractable complex such as LnCR³⁺ was found for La/III/, Ce/III/, Pr/III/, Nd/III/, Sm/III/, and Eu/III/ and also the formation of Ln/CR/ ₂ ³⁺ complexes was suggested for Tb/III/, Tm/III/, and Lu/III/. The extractability of lanthanoid/III/ steeply decreased with increase in the atomic number. This order of extractability was a reverse trend compared with that in many other extraction systems reported so far. Very high separation factors especially among light lanthanoid/III/ were observed.     

Complexes of the Lighter Lanthanoid Nitrates with 15-crown-5 and 18-crown-6 ethers: Synthesis and characterization

Complexes of lanthanoid trinitrates Ln(NO₃)₃ with 15-crown-5 ether 1 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and with 18-crown-6 ether 2 (Ln = La, Ce, Pr, Nd) having a 1:1 stoichiometry as well as 4:3 complexes with 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. All the isolated complexes are solvent free. At 170–220° the 1:1 complexes of 2 are quantitatively transformed into 4:3 complexes. X-Ray powder diagrams of the neodymium complexes with 2 indicate that both the 1:1 and 4:3 complexes are genuine compounds. All the 1:1 complexes show a characteristic IR. absorption band at 875–880 cm^?1 absent from both the spectra of the free ligands and of the 4:3 complexes. The spectroscopic properties (IR. and electronic spectra, fluorescence lifetimes) of the complexes and the low magnetic moments of the Ln(III) ions in the complexes with Ln = Ce-Eu are indicative of a strong interaction between the lanthanoid ions and the crown ethers 1 and 2 .     

Palladium(II)–rare-earth metal(III) paddlewheel carboxylate complexes: Easy total acetate to pivalate metathesis

Bis-paddlewheel heterobimetallic complexes in which palladium(II) is connected to the rare-earth metals(III) [Pd(μ-OOCMe)₄Ln(OH₂)(μ,η²-OOCMe)]₂ × 2HOOCMe (Ln = Nd, Sm, Eu, Yb and Tm) by four acetate bridges were synthesised by the reaction of Pd₃(μ-OOCMe)₆ with the Ln^III acetates. The tetraacetate-bridged complexes were unexpectedly found to be readily transformed by the stoichiometric amount of pivalic acid into the mono-paddlewheel tetrapivalate-bridged analogues in which the paddlewheel structure [Pd(μ-OOCR)₄Ln] maintains as established by X-ray crystallography. The role of the intra- and intermolecular H-bonding in these complexes is discussed.     

Conformational study of lanthanide(III) complexes of N-(2-salicylaldiminatobenzyl)-1-aza-18-crown-6 by using X-ray and ab initio methods

A structural study of lanthanide complexes with the deprotonated form of the monobracchial lariat ether N-2-salicylaldiminatobenzyl-aza-18-crown-6 (L⁴) (Ln = La(III)–Tb(III)) is presented. Attempts to isolate complexes of the heaviest members of the lanthanide series were unsuccessful. The X-ray crystal structures of [Pr(L⁴)(H₂O)](ClO₄)₂ · H₂O · C₃H₈O and [Sm(L⁴)(H₂O)](ClO₄)₂ · C₃H₈O show the metal ion being bound to the eight donor atoms of the ligand backbone. Coordination number nine is completed by the oxygen atom of an inner-sphere water molecule. Two different conformations of the crown moiety (labelled as A and B) are observed in the solid state structure of the Pr(III) complex, while for the Sm(III) complex only conformation A is observed. The complexes were also characterized by means of theoretical calculations performed in vacuo at the HF level, by using the 3-21G^∗ basis set for the ligand atoms and a 46 + 4fⁿ effective core potential for lanthanides. The optimized geometries of the Pr(III) and Sm(III) complexes show an excellent agreement with the experimental structures obtained from X-ray diffraction studies. The calculated relative energies of the A and B conformations for the different [Ln(L⁴)(H₂O)]²⁺ complexes (Ln = La, Pr, Sm, Ho or Lu) indicate a progressive stabilization of the A conformation with respect to the B one upon decreasing the ionic radius of the Ln(III) ion. For the [Ln(L⁴)(H₂O)]²⁺ systems, most of the calculated bond distances between the metal ion and the coordinated donor atoms decrease along the lanthanide series, as usually observed for Ln(III) complexes. However, our ab initio calculations provide geometries in which the Ln–O(5) bond distance [O(5) is an oxygen atom of the crown moiety] increases across the lanthanide series from Sm(III) to Lu(III).     

Preparation and crystal structure of a 1:4 diaqua(benzo-15-crown-5)(perchlorato-<Emphasis Type="Italic">O</Emphasis>)calcium perchlorate and diaqua(4′-nitrobenzo-15-crown-5)(perchlorato-<Emphasis Type="Italic">O</Emphasis>)calcium perchlorate solid solution

A 1:4 diaqua(benzo-15-crown-5)(perchlorato-O)calcium perchlorate and diaqua(4-nitrobenzo-15-crown-5)(perchlorato-O)calcium solid solution [Ca(ClO₄)LH₂O)₂]⁺ClO ₄ ^– [L = (B15C5)_0.2(4-NO₂-B15C5)_0.8] was prepared and studied by X-ray diffraction. The complex cation [Ca(ClO₄)L(H₂O)₂]⁺ is of the guest-host type. The coordination polyhedron of its Ca²⁺ cation is irregular, viz. a distorted prism with two different bases: pentagonal (of five ether oxygen atoms of mixed crown ligand L) and trigonal (of one oxygen atom of the anionic ligand ClO ₄ ^– and two oxygen atoms of the two water molecules). The packing of the complex cations and disordered ClO ₄ ^– anions in the crystal structure of this solid solution was determined to find that these ions are connected by hydrogen bonds into infinite three-dimensional layers.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1244–1249.Original Russian Text Copyright © 2004 by Chekhlov.This revised version was published online in April 2005 with a corrected cover date.     

f-Element/crown ether complexes: 21. Conformational changes in metal complexed versus hydrogen bonded benzo-15-crown-5 in the structure of [Y(OH2)3(NCMe)-(benzo-15-crown-5)][ClO4]3·benzo-15-crown-5·CH3CN

Crystalline [Y(OH₂)₃(NCMe)(benzo-15-crown-5)][ClO₄]₃·benzo-15-crown-5-CH₃CN can be obtained by slowly cooling a reaction mixture of Y(ClO₄)₃·n H₂O with benzo-15-crown-5 in a solution of acetonitrile and methanol (3 : 1) from 60°C to room temperature. The crystal structure of this complex has been determined at –150 and 20°C. The complex is triclinic,P . At –150°C the cell parameters area = 11.986(4),b = 12.071(7),c = 16.364(5) Å, = 93.56(3), = 98.68(3), = 109.68(4)°, vol = 2187 ų, andD _calc = 1.61 g cm^–3 forZ = 2 formula units. 3633 independently observed [F _o 5(F _o)] reflections were used in the final least-squares refinement leading to an agreement index ofR = 0.048. The Y(III) ion coordination geometry approximates a tricapped trigonal prism with three water molecules and three benzo-15-crown-5 oxygen atoms forming the prism, with the two remaining benzo-15-crown-5 oxygen atoms and the acetonitrile molecule completing the coordination as capping atoms. The three water molecules hydrogen bond a second crown ether molecule and two of the perchlorate anions. The two acetonitrile molecules have contacts with perchlorate oxygen atoms close enough for some weak interaction. One perchlorate is ordered, one is partially disordered as is the coordinated solvent molecule, and the third anion is totally disordered. The two unique crown ether molecules have distinctively different conformations.For Part 20, see reference [1].     

Synthesis and characterization of an organometallic Schiff base and its lanthanide chelates

Summary A Schiff base containing an organometallic substituent,N, N-[bis(ferrocenyl-1-oxo-3-methyl)propenyl]ethylenediamine (H₂ bfe) and its chelates with lanthanide(III), [Ln(bfe)]Cl·0–1H₂O (Ln=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu) have been prepared and characterized by elemental analyses, i.r., u.v.,¹H n.m.r., molar conductance, and t.g. analysis. The ligand is a tetradentate species and coordinates to the central lanthanide ion by the oxygen and nitrogen with 11 stoichiometry. The chelates are 11 electrolytes.     

Homolysis of the Ln-N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with 2-pyridylmethyl and 3-pyridylmethyl-functionalized indenyl ligands

Two series of new organolanthanide(II) complexes with general formula {η⁵:η¹-[1-R-3-(2-C₅H₄NCH₂)C₉H₅]}₂Ln(II) (R = H-, Ln = Yb (3), Eu (4); R = Me₃Si-, Ln = Yb (5), Eu (6)), and {η⁵:η¹-[1-R-3-(3-C₅H₄NCH₂)C₉H₅]}₂Ln(II) (R = H-, Ln = Yb (9), Eu (10); R = Me₃Si-, Ln = Yb (11), Eu (12)) were synthesized by silylamine elimination with one-electron reductive reactions of lanthanide(III) amides [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ (Ln = Yb, Eu) with 2 equiv. 1-R-3-(2-C₅H₄NCH₂)C₉H₆ (R = H (1), Me₃Si- (2)) or 1-R-3-(3-C₅H₄NCH₂)C₉H₆ (R = H (7), Me₃Si- (8)) in good yields. All the complexes were fully characterized by elemental analyses and spectroscopic methods. Complexes 3 and 5 were additionally characterized by single-crystal X-ray diffraction study. The catalytic activities of the complexes for MMA polymerization were examined. It was found that complexes with 3-pyridylmethyl substituent on the indenyl ligands could function as single-component MMA polymerization catalysts with good activities, while the complexes with 2-pyridylmethyl substituent on the indenyl ligands cannot catalyze MMA polymerization. The temperatures and solvents effect on the MMA polymerization have also been examined.     

Selective extraction of light lanthanides(III) with 18-crown-6 and perfluorooctanoate

The extraction of La(III), Gd(III), and Lu(III) with 18-crown-6 (18C6) has been studied using pentadecafluorooctanoate (PDFO) as a counter anion. Very high extractability of La(III) was observed in various organic solvents such as benzene, chloroform, 1,2-dichloroethane, and nitrobenzene. The predominant species extracted into benzene was found to be Ln(PDFO)₃ (18C6), and the extraction constants (K _ex,s1 =[Ln(PDFO)₃ (18C6)]_org/[Ln³⁺][PDFO]³[18C6]_org) were 10^13.12 for La(III), 10^9.74 for Gd(III), and 10^9.67 for Lu(III). These values are 10¹⁰ times higher than those in the trichloroacetate-18C6 system reported previously. The present PDFO-18C6 system was superior to the picrate- and hexafluoroacetylacetonate-18C6 system for the separation efficiency of light lanthanides(III).     

Synthesis,Structures, and Luminescent Properties of Chloride and Nitrate LnIII Complexes Coordinated by tris(Pyrazolyl)methane

We report the synthesis of Ln³⁺ nitrate [Ln(Tpm)(NO₃)₃] ⋅ MeCN (Ln=Yb ( 1Yb ), Eu ( 1Eu )) and chloride [Yb(Tpm)Cl₃] ⋅ 2MeCN ( 2Yb ), [Eu(Tpm)Cl₂(μ-Cl)]₂ ( 2Eu ) complexes coordinated by neutral tripodal tris(3,5-dimethylpyrazolyl)methane (Tpm). The crystal structures of 1Ln and 2Ln were established by single crystal X-ray diffraction, while for 1Yb high resolution experiment was performed. Nitrate complexes 1Ln are isomorphous and both adopt mononuclear structure. Chloride 2Yb is monomeric, while Eu³⁺ analogue 2Eu adopts a binuclear structure due to two μ²-bridging chloride ligands. The typical lanthanide luminescence was observed for europium complexes ( 1Eu and 2Eu ) as well as for terbium and dysprosium analogues ([Ln(Tpm)(NO₃)₃] ⋅ MeCN, Ln=Tb ( 1Tb ), Dy ( 1Dy ); [Ln(Tpm)Cl₃] ⋅ 2MeCN, Ln=Tb ( 2Tb ), Dy ( 2Dy )).     

Structural aspects of crown complexes with alkali and alkaline earth cations. Benzo-15-crown-5 as a discriminating macrocycle

X-ray structural results have been reviewed for the related M^z+ L _z ^– -B15C5 complexes where M^z+=Li⁺ to Cs⁺ and Mg²⁺ to Ba²⁺, L^–=2,4,6-trinitrophenolate (Picrate or Pic) and 3,5-dinitrobenzoate (Dnb), and B15C5=benzo-15-crown-5. These results combined with those for come MX_z-B15C5 (X=NCS^–, I^–, NO ₃ ^– , ClO ₄ ^– , BPh ₄ ^– ) complexes have revealed that B15C5 is a useful macrocycle with regard to the within-the-group and between-the-groups discriminations of M^z+ in the solid state.     

Paramagnetic properties and molecular structure of coordination saturated inclusive lanthanide complexes with 18-crown-6 using NMR

Earlier NMR spectra of lanthanide complexes [Ln(18-crown-6)(NO₃)₃] have been analyzed by us (Babailov in Inorg Chem 51(3):1427–1433, 2012), where Ln³⁺ = La³⁺ (I), Ce³⁺ (II), Pr³⁺ (III) and Nd³⁺ (IV). The NMR signal assignment and conformational molecular dynamic have been found by 1D NOE and relaxation spectroscopy as well as on 2D NOESY and EXSY experiments at 170 K. In the present paper the ¹H NMR method is used to study the features of paramagnetic properties of complexes I–IV and [Eu(18-crown-6)(NO₃)₃] (V) at ambient temperature. The investigation was carried out by special method based on analysis of Δδ/z> on k(Ln)/z> (where k(Ln) is Bleaney’s constant, Δδ is paramagnetic contribution to the lanthanide-induced shifts). The obtained results indicate that the structure of the complexes (in CDCl₃ and CD₂Cl₂) are very similar.     

Synergic solvent extraction of some lanthanides with mixtures of thenoyltrifluoroacetone and benzo-15-crown-5

Summary The synergic solvent extraction of Pr, Gd, and Yb with mixtures of thenoyltrifluoroacetone (HTTA) and a crown ether benzo-15-crown-5 (B15C5) in CCl₄, C₆H₆ and CHCl₃ has been studied. The composition of the extracted species has been determined asLn(TTA)₃·2B15C5 (Ln=Pr, Gd, and Yb). The values of the equilibrium constants have been calculated.

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Synergetische Extraktion von Lanthaniden mit Thenoyltrifluoraceton und Benzo-15-crown-5

Zusammenfassung Es wurde die synergetische Extraktion von Pr, Gd und Yb mit Mischungen ausHTTA und Benzo-15-crown-5 in CCl₄, C₆H₆ und CHCl₃ untersucht. Die Zusammensetzung der ExtraktionskomplexverbindungenLn(TTA)₃·2B15C5 (Ln=Pr, Gd und Yb) wurde bestimmt, und die Gleichgewichtskonstanten wurden berechnet.

     

Lanthanide-mediated tuning of electronic and magnetic properties in heterotrimetallic cyclooctatetraenyl multidecker self-assemblies

The synthesis of a novel family of homoleptic COT-based heterotrimetallic self-assemblies bearing the formula [LnKCa(COT)₃(THF)₃] (Ln(iii) = Gd, Tb, Dy, Ho, Er, Tm, and Yb) is reported followed by their X-ray crystallographic and magnetic characterization. All crystals conform to the monoclinic P2₁/c space group with a slight compression of the unit cell from 3396.4(2) ų to 3373.2(4) ų along the series. All complexes exhibit a triple-decker structure having the Ln(iii) and K(i) ions sandwiched by three COT²⁻ ligands with an end-bound {Ca²⁺(THF)₃} moiety to form a non-linear (153.5°) arrangement of three different metals. The COT²⁻ ligands act in a η⁸-mode with respect to all metal centers. A detailed structural comparison of this unique set of heterotrimetallic complexes has revealed consistent trends along the series. From Gd to Yb, the Ln to ring-centroid distance decreases from 1.961(3) Å to 1.827(2) Å. In contrast, the separation of K(i) and Ca(ii) ions from the COT-centroid (2.443(3) and 1.914(3) Å, respectively) is not affected by the change of Ln(iii) ions. The magnetic property investigation of the [LnKCa(COT)₃(THF)₃] series (Ln(iii) = Gd, Tb, Dy, Ho, Er, and Tm) reveals that the Dy, Er, and Tm complexes display slow relaxation of their magnetization, in other words, single-molecule magnet (SMM) properties. This behaviour is dominated by thermally activated (Orbach-like) and quantum tunneling processes for [DyKCa(COT)₃(THF)₃] in contrast to [ErKCa(COT)₃(THF)₃], in which the thermally activated and Raman processes appear to be relevant. Details of the electronic structures and magnetic properties of these complexes are further clarified with the help of DFT and ab initio theoretical calculations.

A new class of heterotrimetallic COT-based self-assemblies accommodates metals from groups I–III in three different oxidation states and enables tuning of electronic and magnetic properties.     

Synthesis and properties of homoleptic 2,2′-bipyridyl complexes of rare-earth elements. Crystal and molecular structures of the complexes Ln(N2C10H8)4 (Ln=Sm, Eu, Yb, or Lu) and the ionic complex [Lu(N2C10H8)4][Li(THF)4]

Homoleptic 2,2′-bipyridyl complexes of lanthanides (Ln), Ln(bpy)₄, were prepared by the reactions of iodides LnI₂(THF)₂ (Ln=Sm, Eu, Tm, or Yb), LnI₃(THF)₃ (Ln=La, Ce, Pr, Nd, Gd, or Tb), or bis(trimethylsilyl)amides Ln[N(SiMe₃)₂]₃ (Ln=Dy, Ho, Er, or Lu) with bipyridyllithium in tetrahydrofuran (THF) or 1,2-dimethoxyethane in the presence of free 2,2′-bipyridine. The IR and ESR spectral data, the magnetic susceptibilities, and the results of X-ray diffraction analysis indicate that the complexes of all elements of the lanthanide series, except for the europium complex, contain Ln⁺³ cations and anionic bpy ligands. According to the X-ray diffraction data, the coordination polyhedra about the Sm and Eu atoms are cubes, whereas the environment about the Yb atom is a distorted dodecahedron. In the ionic complex [Lu(bpy)₄][Li(THF)₄], the geometry of the [Lu(bpy)₄]⁻ anion is similar to that of the Lu(bpy)₄ complex. The possible modes of charge distributions over the ligands,viz., Ln(bpy²⁻)(bpy^.−)(bpy⁰)₂ and Ln(bpy^.−)₃(bpy⁰), are discussed. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1897–1904, November, 2000.