New lanthanide(III) disiloxanediolates: Syntheses and structures

Three new chloro-functionalized lanthanide(III) bis(disiloxanediolate) complexes, [{(Ph₂SiO)₂O}₂{Li(DME)}₂]Nd(DME)Cl (3), [{(Ph₂SiO)₂O}₂{Li(THF)₂}₂]HoCl·2THF (4), and [{(Ph₂SiO)₂O}₂{Li(THF)₂}₂]ErCl·2THF (5) have been prepared by the treatment of anhydrous lanthanide trichlorides, LnCl₃ (Ln = Nd, Ho, Er), with two equivalents of in situ prepared (Ph₂SiOLi)₂O (2). In a similar manner, the treatment of PrCl₃ with 2 equivalents of (Ph₂SiOLi)₂O (2) in the presence of LiN(SiMe₃)₂ afforded the silylamide-functionalized derivative [{(Ph₂SiO)₂O}₂{Li(THF)₂}₂]Pr[N(SiMe₃)₂] (6). All new compounds have been structurally characterized by X-ray diffraction analyses. Compounds 4 and 5 represent a new intermediate structural type of lanthanide bis(disiloxanediolates) between the “inorganic metallocenes” (Pr, Nd, Sm) and the “metallacrowns” (Sc, Y).     

Syntheses, crystal structures and luminescent properties of new lanthanide(III) organoarsonates

The first examples of lanthanide(III) organoarsonates, Ln(L(1))(H(2)O)(3) (Ln = La (1), H(3)L(1) = 4-hydroxy-3-nitrophenylarsonic acid), Ln(L(1))(H(2)O)(2) (Ln = Nd (2), Gd (3)), and mixed-ligand lanthanide(III) organoarsonates, Ln(2)(HL(1))(2)(C(2)O(4))(H(2)O)(2) (Ln = Nd (4), Sm (5), Eu (6)), were hydrothermally synthesized and structurally characterized. Compounds 1-3 feature a corrugated lanthanide arsonate layer, in which 1D lanthanide arsonate inorganic chains are further interconnected via bridging L(1)(3-) ligands. Compounds 4-6 exhibit a complicated 3D network. The interconnection of the lanthanide(III) ions by the bridging arsonate ligand leads to the formation of a novel 3D framework with long narrow 1D tunnels along the a-axis, with the oxalate anions are located at the above tunnels and bridging with lanthanide(III) ions. Compounds 2 and 4 exhibit the characteristic emission bands of the Nd(III) ion, whereas compound 6 displays the characteristic emission bands of the Eu(III) ion. The magnetic properties of compounds 3-6 were also investigated.     

Surprising coordination for plutonium in the first plutonium(III) borate

The first plutonium(III) borate, Pu(2)[B(12)O(18)(OH)(4)Br(2)(H(2)O)(3)]·0.5H(2)O, has been prepared by reacting plutonium(III) with molten boric acid under strictly anaerobic conditions. This compound contains a three-dimensional polyborate network with triangular holes that house the plutonium(III) sites. The plutonium sites in this compound are 9- and 10-coordinate and display atypical geometries.     

Crystal structures of some lanthanide(III) complexes with acylhydrazone and their coordination chemistry

Three new lanthanide(III) complexes with N-(2-propionic acid)-salicyloylhydrazone (H₂L, C₁₀H₁₀N₂O₄) ligand [La(HL)₂(NO₃)(H₂O)₂]₃ ·4H₂O(I), [Gd(HL)₃] · 2(C₂H₅)₃ N(II) and [Er(L)(HL)(H₂O)₂] · 2H₂O(III) has been synthesized and characterized by elemental analyses, IR, UV, and molar conductivity. The crystal structures of three complexes have been determined by X-ray single-crystal diffractometer. In complex I, the La³⁺ ion is ten-coordinated by two tridentate ligands, one bidentate nitrate, and two water molecules. In complex II, the Gd³⁺ ion has a coordination number of nine by three tridentate ligands. In complex III, the Er³⁺ ion is eight-coordinated by two tridentate ligands and two water molecules. In all structures, tridentate ligands are coordinated by carboxyl O and acyl O atoms and azomethine N atom to form two stable five-membered rings sharing one side in the keto mode as indicated by the results of crystal structures and infrared spectral analysis.     

Effects of Fe(III) ions on the electrodeposition of trace amounts of plutonium and americium

The electrodeposition of Pu and Am onto stainless steel discs from 3.2M ammonium chloride solution is strongly affected by the iron concentration of the electrolyte. At Fe(III) concentrations of more than 0.1mM (30 g Fe in 5 ml) only 30–40% of²³⁶Pu and 6% of²⁴¹Am can be deposited. Tracer experiments with⁵⁹Fe suggest that exchange processes take place between Fe from the surface layer of the cathode and from the electrolyte. Double tracer studies show increasing²³⁶Pu/⁵⁹Fe- and decreasing²⁴¹Am/⁵⁹Fe-ratios with increasing iron content of the electrolyte, which may be due to different sorption properties on colloidal iron hydroxides formed at pH<3.6.     

Reaction of lanthanide(II) and lanthanide(III) phenylethynyl cuprates with acetyl chloride

Praseodymium and ytterbium phenylethynyl cuprates [(PhC≡C)₃Cu]₃Pr₂(THF)₆ and {[(PhC≡C)₃Cu]·Yb(THF)₂}₂ react with acetyl chloride in tetrahydrofuran with elimination of phenylethynylcopper and formation of alkoxides [PhC≡C-CCl(CH₃)O] _n Ln (n = 3, Ln = Pr; n = 2, Ln = Yb). Then praseodymium alkoxide forms ester [methyl (phenylethynyl)chloromethylethanoate] and praseodymium chloride, alkoxy derivative. Itterbium alkoxide is oxidized to unsymmetrical dialkoxyitterbium chloride PhC≡C-CH(CH₃)-O-Yb(Cl)-O-CCl(CH₃)C≡CPh·2THF.     

An intermediate neglect of differential overlap (INDO) technique for lanthanide complexes: studies on lanthanide halides

An intermediate neglect of differential overlap method of use for examining the electronic structure of lanthanide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac-Fock atomic calculations, the inclusion of all one-center two-electron integrals, and a parameter set based on molecular geometry.Lanthanide halides MX₂, MX₃ and MX₄ are studied here, as well as initial results for the twelve coordinate Ce(NO₃)₆ ^–2 ion. Geometries obtained are in excellent agreement with experimental values when available. Many MX₃ complexes are found to be pyramidal, and EuCl₂ and YbCl₂ are calculated to be bent even at the SCF level. Models invoking London type forces are therefore not required. Ionization potentials are calculated for the trihalides (SCF) and are in reasonable agreement with experiment.Contrary to conclusion of others, f-orbital participation, although small, is required — at least in this model — to obtain the spread of metal to halide bond distance observed in these complexes. However f-orbital participation does not seem to be significant even in the twelve coordinate Ce(NO₃)₆ ^–2 complex: rather the large coordination number seems to be a consequence of the relatively large size of the lanthanide ion.     

Stabilization of plutonium(III) in the Preyssler polyoxometalate

The Na(+) ion encapsulated within the Preyssler heteropolyoxoanion, [NaP5W30O110](14-), was exchanged with Pu(III) under hydrothermal conditions to obtain [Pu(III)P5W30O110](12-) (abbreviated [PuPA](12-)) with hybrid electrochemical properties resulting from the combination of the key redox behaviors of the Pu cation and the P-W-O anion. The electroanalytical chemistry of this two-center, multielectron redox system in a 1 M HCl electrolyte shows that Pu(III) is oxidized to Pu(IV) at the half-wave potential, E(1/2), of +0.960 V versus Ag/AgCl, which is 0.197 V more positive than the corresponding electrode potential for the Pu(III) aqua ion also in 1 M HCl, indicating the stabilization of the trivalent Pu cation by its encapsulation in the Preyssler polyoxometalate (POM). This effect is uncommon in actinide-POM chemistry, wherein electrode potential shifts of the opposite nature (to more negative values), leading to the stabilization of the tetravalent ions by complexation, are renowned. Moreover, in cyclic voltammetry measurements of the Pu(III) aqua ion and [PuPA](12-), the peak currents, i(p), for the one-electron Pu(III)/Pu(IV) processes show different dependencies with the scan rate, nu. The former shows proportionality with nu(1/2), indicating freely diffusing species, whereas the latter shows proportionality with nu, indicating a surface-confined one. The first of the five successive two-electron, W-centered reduction processes in [PuPA](12-) occurs at E(1/2) = -0.117 V versus Ag/AgCl, which is 1.077 V less than the E(1/2) for the Pu(III)/Pu(IV) oxidation, thereby providing an experimental, electrochemical measure of the highest occupied molecular orbital/lowest unoccupied molecular orbital energy gap, which compares well with values previously obtained by density-functional theory, complete active space-self consistent field, and post-Hartree-Fock calculations for a series of M(n+)-exchanged systems, [MPA](n-15) for 1 < or = n < or = 4 (Fernandez, J. A.; Lopez, X.; Bo, C.; de Graff, C.; Baerends, E. J.; Poblet, J. M. J. Am Chem. Soc. 2007, 129, 12244-12253). It was not possible to prepare the Np-exchanged Preyssler anion in the manner of [PuPA](12-), because of the instability of tri- and tetravalent Np to oxidation and the formation of the neptunyl(V) ion, which also could not be exchanged for Na(+).     

Photo and electroluminescence of lanthanide(III) complexes

Major classes of coordination compounds used as electroluminescent materials are surveyed, and their advantages and disadvantages are discussed. The strategy of the directed synthesis of lanthanide(III) complexes promising for use as electroluminescent materials is formulated. The results of studies dealing with the design of electroluminescent devices based on europium(III), terbium(III), and thulium(III) complexes are considered.     

A study on the fluoride complexes of plutonium(III), samarium(III) and bismuth(III) using fluoride ion-selective potentiometry

Stability constants of the fluoride complexes of Pu(III), Sm(III) and Bi(III) in 1.0M NaClO₄/HClO₄ medium at 23±1°C have been determined by potentiometry using a fluoride ion-selective electrode. Plutonium was reduced to the trivalent state using quinhydrone with an excess to serve as holding reductant. The log values of concentration stability constants log ₁, log ₂, and log ₃ are 3.58, 6.40 and 12.61 for Pu(III), 3.23, 5.81 and 10.54 for Sm(III) and 3.69, 6.13 and 11.04 for Bi(III), respectively. The log ₂ values in all these cases have very large deviation and may be taken only as rough estimates.     

Heterometallic cubanes: syntheses, structures, and magnetic properties of lanthanide(III)-nickel(II) architectures

Reactions of lanthanide(III) perchlorate (Ln = Dy, Tb, and Gd), nickel(II) acetate, and ditopic ligand 2-(benzothiazol-2-ylhydrazonomethyl)-6-methoxyphenol (H(2)L) in a mixture of methanol and acetone in the presence of NaOH resulted in the successful assembly of novel Ln(2)Ni(2) heterometallic clusters representing a new heterometallic 3d-4f motif. Single-crystal X-ray diffraction reveals that all compounds are isostructural, with the central core composed of distorted [Ln(2)Ni(2)O(4)] cubanes of the general formula [Ln(2)Ni(2)(μ(3)-OH)(2)(OH)(OAc)(4)(HL)(2)(MeOH)(3)](ClO(4))·3MeOH [Ln = Dy (1), Tb (2), and Gd (3)]. The magnetic properties of all compounds have been investigated. Magnetic analysis on compound 3 indicates ferromagnetic Gd···Ni exchange interactions competing with antiferromagnetic Ni···Ni interactions. Compound 1 displays slow relaxation of magnetization, which is largely attributed to the presence of the anisotropic Dy(III) ions, and thus represents a new discrete [Dy(2)Ni(2)] heterometallic cubane exhibiting probable single-molecule magnetic behavior.     

Thiosemicarbazide complexes of antimony(III) halides

Some hitherto unknown complexes of thiosermicarbazide (Htsc) and antimony(III) halides have been synthesized in 1,4-dioxane. The elemental analyses have indicated that these compounds are of the type Sb(CH₅N₃S)Cl₃ and Sb(CH₅N₃S)X₃.C₄H₈O₂, where X = Br or I. The electronic and vibration spectral analyses have shown that Htsc acts as a bidentate ligand in these complexes, linking through sulphur and “the hydrazine terminal nitrogen” to Sb(III).     

Extraction behavior of Tm(III), Dy(III) and Sm(III) lanthanide with N-benzoyl-N-phenylhydroxalamine

The extraction of Sm(III), Dy(III) and Tm(III) with N-benzoyl-N-phenylhydroxalamine (BPHA) in benzene at pH range (1–10) has been studied. Quantitative separation was found in borate media at pH 8. The slope analysis showed that the extracted complex was M(BPHA)₃, where M=Sm(III), Dy(III) and Tm(III). The effect of various masking agents indicated that EDTA, oxalate, fluoride, phosphate and citrate, interfered in this study. Decontamination study showed that Cu(II), Zn(II), Ni(II), Co(II), Cr(III), Sc(III) and Fe(III) had very poor separation factors, whereas Sn(II), Cd(II), In(III), Ru(II), Hg(II), Ag(I), Ta(V) and Hf(IV) had very large separation factor. The effect of different diluents showed that carbontetrachloride, chloroform, benzene, toluene, nitrobenzene dichloromethane, MIBK and cyclohexanone were equally good for extraction except TBP due to ion association.     

Oxidation of plutonium by cobalt(III) green

A stable green solution of tricarbonatocobaltate(III) has been prepared and used for the redox titrimetric determination of plutonium in HNO₃ medium. Quantitative oxidation could be achieved and excess oxidant could be destroyed by NaNO₂. Pu(VI) was deter-ined by adding known excess of Fe(II) and carrying out potentiometric titration. The precision at the level of 0.5–5.0 mg was 2% RSD.     

Syntheses and structures of lanthanide(III) complexes with some bis(pyrazolyl)borate and tris(pyrazolyl)borate podand ligands

Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4-^tbutyl)-pyrid-2-yl}-pyrazol-1-yl]hydroborate (KTp^BuPy) which has three bidentate arms and is therefore hexadentate; and potassium bis[3-(2-pyridyl)-5-(methoxymethyl)pyrazol-1-yl]-dihydroborate (KBp^(COC)Py) which has two bidentate arms and is therefore tetradentate. The crystal structures of their lanthanide complexes [La(Tp^BuPy)(NO₃)₂] and [La(Bp^(COC)Py)₂X] (X=nitrate or triflate) have been determined. In [La(Tp^BuPy)(NO₃)₂] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp^(COC)Py)₂(NO₃)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp^(COC)Py)₂(CF₃SO₃)] the metal ion is nine-coordinate because the triflate anion is monodentate. Two unexpected new complexes which arose from partial decomposition of the poly(pyrazolyl)borate ligands have also been characterised structurally. In [La(^BuPypzH)₃(O₃SCF₃)₃] the metal ion is nine-coordinate from three bidentate pyrazolyl-pyridine arms (liberated by decomposition of KTp^BuPy) and three triflate anions; there is extensive NH· · · O hydrogen-bonding between the pyrazolyl and triflate ligands. [Nd(Tp^Py)(Bp^Py)][Nd(PypzH)(NO₃)₄] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-yl]hydroborate (Tp^Py) with Nd(NO₃)₃. One of the Tp^Py ligands has lost one bidentate pyrazolyl-pyridine ‘arm’ (PypzH) to leave tetradentate tris[3-(2-pyridyl)-pyrazol-1-yl]dihydroborate (Bp^Py). In this structure, the cation [Nd(Tp^Py)(Bp^Py)]⁺ is ten-coordinate from inter-leaved hexadentate and tetradentate ligands, and the anion [Nd(PypzH)(NO₃)₄]⁻ is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates.     

Solvent extraction of trivalent lanthanide Pr(III), Ho(III) and Er(III) with N-benzoyl-N-phenylhydroxylamine

Extraction of Pr(III), Ho(III) and Er(III) has been studied in the pH range of 1–10 with N-benzoyl-N-phenylhydroxylamine (BPHA) in benzene. The separation was found to be quantitative in borate media from pH 7 to 10, at an ionic strength of 0.1M (H⁺, BO₃ ^3–). The stoichiometric composition of the complexes under the optimal conditions of shaking time, pH and reagent concentration was formulated using slope analysis and found to be M(BPHA)₃, where M=Pr(III), Ho(III) and Er(III). The effect of various masking agents shows that citrate, ascorbate, EDTA, oxalate, fluoride and phosphate form stable complexes with these rare earths as compared to BPHA. The decontamination factors for different cations with respect to these rare earths under the optimum conditions have been evaluated.     

Crystal structures of lanthanide(III) complexes with cyclen derivative bearing three acetate and one methylphosphonate pendants

A series of lanthanide(III) complexes formulated as M[Ln(Hdo3ap)].xH(2)O (M = Li or H and Ln = Tb, Dy, Er, Lu, and Y) with the monophosphonate analogue of H(4)dota, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-methylphosphonic acid (H(5)do3ap), was prepared in the solid state and studied using X-ray crystallography. All of the structures show that the (Hdo3ap)(4-) anion is octadentate coordinated to a lanthanide(III) ion similarly to the other H(4)dota-like ligands, i.e., forming O(4) and N(4) planes that are parallel and have mutual angle smaller than 3 degrees . The lanthanide(III) ions lie between these planes, closer to the O(4) base than to the N(4) plane. All of the structures present the lanthanide(III) complexes in their twisted-square-antiprismatic (TSA) configuration. Twist angles of the pendants vary in the range between -24 and -30 degrees, and for each complex, they lie in a very narrow region of 1 degree. The coordinated phosphonate oxygen is located slightly above (0.02-0.19 Angstroms) the O(3) plane formed with the coordinated acetates. A water molecule was found to be coordinated only in the terbium(III) and neodymium(III) complexes. The bond distance Tb-O(w) is unusually long (2.678 Angstroms). The O-Ln-O angles decrease from 140 degrees [Nd(III)] to 121 degrees [Lu(III)], thus confirming the increasing steric crowding around the water binding site. A comparison of a number of structures of Ln(III) complexes with DOTA-like ligands shows that the TSA arrangement is flexible. On the other hand, the SA arrangement is rigid, and the derived structural parameters are almost identical for different ligands and lanthanide(III) ions.