Structural Characterization of Methanol Substituted Lanthanum Halides

Heterometallic 3d-4f Alkoxide Precursors for the Synthesis of Binary Oxide Nanomaterials

In this study, a new method for the synthesis of heterometallic 3d-4f alkoxides by the direct reaction of metallic lanthanides (La, Pr, Nd, Gd) with MCl₂ (M = Mn, Ni, Co) in 2-methoxyethanol was developed. The method was applied to the synthesis of the heterometallic oxo-alkoxide clusters [Ln₄Mn₂(μ₆-O)(μ₃-OR)₈(HOR)_xCl₆] (Ln = La (1), Nd (2), Gd (3); x = 0, 2, 4); [Pr₄M₂(μ₆-O)(μ₃-OR)₈(HOR)_xCl₆] (M = Co (4), Ni (5); x = 2, 4); and [Ln₄Mn₂(μ₃-OH)₂(μ₃-OR)₄(μ-OR)₄(μ-Cl)₂(HOR)₄Cl₆] (Ln = La (11) and Pr (12)). Mechanistic investigation led to the isolation of the homo- and heterometallic intermediates [Pr(μ-OR)(μ-Cl)(HOR)Cl]_n (6), [Co₄(μ₃-OR)₄(HOR)₄Cl₄] (7), [Ni₄(μ₃-OR)₄(HOEt)₄Cl₄] (8), [Mn₄(μ₃-OR)₄(HOR)₂(HOEt)₂Cl₄] (9), and [Nd(HOR)₄Cl][CoCl₄] (10). In the presence of an external M(II) source at 1100 °C, 1-4 and 12 were selectively converted into binary metal oxide nanomaterials with trigonal or orthorhombic perovskite structures, i.e., LaMnO₃, GdMnO₃, NdMnO₃, Pr_0.9MnO₃, and PrCoO₃. Compound 5 decomposed into a mixture of homo- and heterometallic oxides. The method presented provides a valuable platform for the preparation of advanced heterometallic oxide materials with promising magnetic, luminescence, and/or catalytic applications.

Rare Earth Starting Materials and Methodologies for Synthetic Chemistry

The number of rare earth (RE) starting materials used in synthesis is staggering, ranging from simple binary metal-halide salts to borohydrides and "designer reagents" such as alkyl and organoaluminate complexes. This review collates the most important starting materials used in RE synthetic chemistry, including essential information on their preparations and uses in modern synthetic methodologies. The review is divided by starting material category and supporting ligands (i.e., metals as synthetic precursors, halides, borohydrides, nitrogen donors, oxygen donors, triflates, and organometallic reagents), and in each section relevant synthetic methodologies and applications are discussed.

Diethyl ether adducts of trivalent lanthanide iodides

The synthesis and structural characterization of molecular complexes of lanthanide iodides supported by the weak-base, diethyl ether, are reported.

Isomorphous rare-earth tris[bis(2,6-diisopropylphenyl) phosphate] complexes and their catalytic properties in 1,3-diene polymerization and in the inhibited oxidation of polydimethylsiloxane

Crystals of mononuclear tris[bis(2,6-diisopropylphenyl) phosphato-κO]pentakis(methanol-κO)lanthanide methanol monosolvates of lanthanum, [La(C₂₄H₃₄O₄P)₃(CH₃OH)₅]·CH₃OH, (1), cerium, [Ce(C₂₄H₃₄O₄P)₃(CH₃OH)₅]·CH₃OH, (2), and neodymium, [Nd(C₂₄H₃₄O₄P)₃(CH₃OH)₅]·CH₃OH, (3), have been obtained by reactions between LnCl₃(H₂O)_n (n = 6 or 7) and lithium bis(2,6-diisopropylphenyl) phosphate in a 1:3 molar ratio in methanol media. Compounds (1)-(3) crystallize in the monoclinic P2₁/c space group and have isomorphous crystal structures. All three bis(2,6-diisopropylphenyl) phosphate ligands display a κO-monodentate coordination mode. The coordination number of the metal atom is 8. Each [Ln{O₂P(O-2,6-ⁱPr₂C₆H₃)₂}₃(CH₃OH)₅] molecular unit exhibits four intramolecular O-H...O hydrogen bonds, forming six-membered rings. The unit forms two intermolecular O-H...O hydrogen bonds with one noncoordinating methanol molecule. All six hydroxy H atoms are involved in hydrogen bonding within the [Ln{O₂P(O-2,6-ⁱPr₂C₆H₃)₂}₃(CH₃OH)₅]·CH₃OH unit. This, along with the high steric hindrance induced by the three bulky diaryl phosphate ligands, prevents the formation of a hydrogen-bond network. Complexes (1)-(3) exhibit disorder of two of the isopropyl groups of the phosphate ligands. The cerium compound (2) demonstrates an essential catalytic inhibition in the thermal decomposition of polydimethylsiloxane in air at 573 K. Catalytic systems based on the neodymium complex tris[bis(2,6-diisopropylphenyl) phosphato-κO]neodymium, (3'), which was obtained as a dry powder of (3) upon removal of methanol, display a high catalytic activity in isoprene and butadiene polymerization.

Small-Scale Metal-Based Syntheses of Lanthanide Iodide, Amide, and Cyclopentadienyl Complexes as Analogues for Transuranic Reactions

Small-scale reactions of the Pu analogues La, Ce, and Nd have been explored in order to optimize reaction conditions for milligram scale reactions of radioactive plutonium starting from the metal. Oxidation of these lanthanide metals with iodine in ether and pyridine has been studied, and LnI₃(Et₂O)_x (1-Ln; x = 0.75-1.9) and LnI₃(py)₄ (2-Ln; py = pyridine, NC₅H₅) have been synthesized on scales ranging from 15 mg to 2 g. The THF adducts LnI₃(THF)₄ (3-Ln) were synthesized by dissolving 1-Ln in THF. The viability of these small-scale samples as starting materials for amide and cyclopentadienyl f-element complexes was tested by reacting KN(SiMe₃)₂, KCp' (Cp' = C₅H₄SiMe₃), KCp'' (Cp'' = C₅H₃(SiMe₃)₂-1,3), and KC₅Me₄H with 1-Ln generated in situ. These reactions produced Ln[N(SiMe₃)₂]₃ (4-Ln), Cp'₃Ln (5-Ln), Cp″₃Ln (6-Ln), and (C₅Me₄H)₃Ln (7-Ln), respectively. Small-scale samples of Cp'₃Ce (5-Ce) and Cp'₃Nd (5-Nd) were reduced with potassium graphite (KC₈) in the presence of 2.2.2-cryptand to check the viability of generating the crystallographically characterizable Ln²⁺ complexes [K(2.2.2-cryptand)][Cp'₃Ln] (8-Ln; Ln = Ce, Nd).

Solubility of rare earth metal bromides and iodides in aqueous systems

Abstract

The International Union of Pure and Applied Chemistry (IUPAC) project of collection, compilation, and critical evaluation of solubility data of bromides and iodides of the scandium group and all lanthanides in water and aqueous systems containing either halide acids, halide salts, or organic compounds is under preparation. As a result of their similarity to the chlorides, which were recently evaluated, the bromides and iodides in the lanthanide series should show some regularities in their solubility data. Unfortunately, the corresponding results show a large scatter when ordered according to the atomic number. Thus, it is complicated to select the best data for recommendation. Reasons for the inaccuracy of solubility measurements are outlined. In fact some solubility values of bromides predicted by correlation with chlorides seem to be more reliable than the experimental ones. As sufficient experimental data at various temperatures were available, the water-rich fragment of the LaBr₃–H₂O equilibrium phase diagram has been formed and depicted. It seems to be similar to the well-known LaCl₃–H₂O diagram. Several regularities, with respect to stoichiometry and solubility of compounds formed, were observed during investigations of the aqueous ternary systems. The complex iodides of various lanthanides display more regularities in their properties than the bromides do.

Graphical abstract