New Complexes of Rare Earth Elements with 3-Methyladipic Acid

Rare earth element 3-methyladipates were prepared as crystalline solids with general formula Ln₂(C₇H₁₀O₄)₃⋅nH₂O, where n=6 for La, n=4 for Ce,Sm–Lu, n=5 for Pr, Nd and n=5.5 for Y. Their solubilities in water at 293 K were determined (2⋅10^–3–1.5⋅10^–4 mol dm^–3). The IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. During heating the hydrated 3-methyladipates lose all crystallization water molecules in one (Ce–Lu) or two steps (Y) (except of La(III) complex which undergoes tomonohydrate) and then decompose directly to oxides (Y, Ce) or with intermediate formation of oxocarbonates Ln₂O₂CO₃ (Pr–Tb) or Ln₂O(CO₃)₂ (Gd–Lu). Only La(III) complex decomposes in four steps forming additionally unstable La₂(C₇H₁₀O₄)(CO₃)₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal and Spectral Studies of Y(III) and Lanthanide(III) Complexes with Mesaconic Acid

Y(III) and lanthanide(III) mesaconates were prepared as crystalline solids with general formula Ln₂(C₅H₄O₄)₃⋅nH₂O, where n=7 for La−Pr, n=4 for Y,Nd−Ho, n=8 for Er−Lu. IR spectra of the prepared mesaconates suggest that carboxylate groups are bidentate bridging anf chelating. During heating the hydrated complexes are dehydrated in one (Y, Nd−Lu) or two steps (La−Pr) and then decompose directly to oxides (Y, Ce, Pr, Sm, Gd−Lu) or with intermediate formation Ln₂O₂CO₃ (La, Nd, Eu). This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectral and Thermal Studies of Rare Earth Element 3-methylglutarates

Conditions for the formation of rare earth element (Y, La–Lu) 3-methylglutarates were studied and their quantitative composition and solubilities in water at 293 K were determined (10^–2 mol dm^–3). The IR spectra of the prepared complexes with general formula Ln₂(C₆H₈O₄)₃ nH₂O (n=3–8) were recorded and their thermal decomposition in the air were investigated. During heating the hydrated 3-methylglutarates are dehydrated in one step and next anhydrous complexes decompose to oxides Ln₂O₃ with intermediate formation Ln₂O₂CO₃ (Y, La, Nd–Gd) or directly to the oxides, Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ (Ce, Pr, Tb–Lu). This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis And Characterization Of Complexes Of Rare Earth Elements With 1,1-Cyclobutanedicarboxylic Acid

The complexes of yttrium and lanthanide with 1,1-cyclobutanedicarboxylic acid of the formula: Ln₂(C₆H₆O₄)₃⋅nH₂O, where n=4 for Y, Pr–Tm, n=5 for Yb,Lu, n=7 for La, Ce have been studied. The solid complexes have colours typical of Ln³⁺ ions. During heating in air they lose water molecules and then decompose to the oxides, directly (Y, Ce, Tm, Yb) or with intermediate formation. The thermal decomposition is connected with released water (313–353 K), carbon dioxide, hydrocarbons(538–598 K) and carbon oxide for Ho and Lu. When heated in nitrogen they dehydrate to form anhydrous salt and next decompose to the mixture of carbon and oxides of respective metals. IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structural and thermal properties of rare earth complexes with 2,2′-biphenyldicarboxylic acid

Rare earth complexes with 2,2′-biphenyldicarboxylic acid (diphenic acid = H₂dpa) were obtained as hydrated precipitates of the general formula Ln₂(C₁₄H₈O₄)₃∙nH₂O, where n = 3 for the of Y(III) and Ce(III)–Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30–210 °C in one step and form anhydrous compounds, which are stable up to 315–370 °C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)–Er(III) complexes) crystal systems.     

Preparation, Spectral and Thermal Studies of Y(III) and Lanthanide(III) 1-Hydroxy-2-Naphthoates

Complexes of lanthanide(III) (La–Lu) and Y(III) with 1-hydroxy-2-naphthoic acid were obtained as crystalline compounds with a general formula Ln[C₁₀H₆(OH)COO]₃⋅nH₂O:n=6 for La–Tm and Y, n=2 for Yb and n=0 for Lu. IR spectra of the prepared complexes were recorded, and their thermal decomposition in air were investigated. Spectroscopic data suggest that in the coordination of metal-organic ligand only oxygen atoms from the carboxylate group take part. When heated, the complexes decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ with intermediate formation of Ln(C₁₁H₇O₃)(C₁₁H₆O₃). This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

---

Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Thermal and Spectral Features of Yttrium and Heavy Lanthanide Complexes with 2,4-dimethoxybenzoic Acid

The complexes of yttrium and heavy lanthanides with 2,4-dimethoxybenzoic acid of the formula: Ln(C₉H₉O₄)₃×nH₂O, where Ln=Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(III), n=2 for Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Y(III), and n=0 for Yb(III) and Lu(III), have been synthesized and characterized by elemental analysis, IR spectroscopy, themogravimetric studies, as well as X–ray and magnetic susceptibility measurements. The complexes have a colour typical of Ln ³⁺ salts (Tb, Dy, Tm, Yb, Lu, Y – white, Ho – cream, Er – pink). The carboxylate group in these complexes is a bidentate, chelating ligand. The compounds form crystals of various symmetry. 2,4-Dimethoxybenzoates of Yb(III) and Lu(III) are isostructural. 2,4-Dimethoxybenzoates of yttrium and heavy lanthanides decompose in various ways on heating in air to 1173 K. The hydrated complexes first lose water to form anhydrous salts and then decompose to the oxides of respective metals. The ytterbium and lutetium 2,4-dimethoxybenzoates decompose in one step to form Yb₂O₃ and Lu₂O₃. The solubilities of the 2,4-dimethoxybenzoates of yttrium and heavy lanthanides in water and ethanol at 293 K are of the order of: ^10–3 and 10^–3 –10^–2 mol dm^–3, respectively. The magnetic moments for the complexes were determined over the range of 77–298 K. They obey the Curie–Weiss law. The results show that there is no influence of the ligand field on the 4f electrons of lanthanide ions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preparation and study of rare earth 4-aminosalicylates

Summary p-Aminosalicylates of Y, La and lanthanides prepared in the reaction of the ammoniump-aminosalicylate and lanthanide chlorides in solutions have the general formulaLn(C₇H₆O₃N)₃·nH₂O, wheren=3 for La, Ce;n=2 for Pr, Nd, Sm, Eu;n=0 for Y, Gd—Lu. Their solubilities in water are of the order of 10^–3 mol dm^–3. Heating above 350–450 K leads to dehydration and decomposition at the same time. The IR and X-ray spectra for the obtained complexes were recorded. It was found that only complexes of La—Nd are crystalline compounds. The way of metal-ligand coordination is discussed.

---

Darstellung und Charakterisierung der Komplexe von Seltenen Erdmetallen mitp-Aminosalicylsäure

Zusammenfassung Zur Darstellung der Verbindungen des TypsLn(C₇H₆O₃N)₃·nH₂O (mitn=3 für La, Ce;n=2 für Pr, Nd, Sm, Eu;n=0 für Y, Gd—Lu) wurde die berechnete Menge von Ammonium-p-aminosalicylat undLnCl₃-Lösungen beipH5.8 gemischt und zur Kristallisation gebracht. Ihre Wasserlöslichkeit bei 298 K ist in der Größenordnung 10^–3 mol dm^–3. Beim Erhitzen erfolgt bei 350–450 K Entwässerung und Zersetzung zugleich. Die Infrarot- und Röntgenspektren der erhaltenen Komplexe wurden gemessen und dabei festgestellt, daß nur die La—Nd-Komplexe kristalline Verbindungen sind. Die Art der Koordination der Seltenerdmetalle mit den Liganden wird diskutiert.

     

Thermal decomposition of 4,4′-dipyridyl complexes of light rare-earth thiocyanates in air atmosphere

The thermal decompositions of Ln(NCS)₃(4-dipy)₂·5H₂O were studied, whereLn=La, Pr, Nd, Sm, Eu and Y, and 4-dipy=4,4′-dipyridyl. The compounds are first dehydrated. During the thermal decomposition of Ln(NCS)₃(4-dipy)₂, deamination takes place. The transient products decompose with the formation of Ln₂O₂SO₄. The energies of activation for the first step of dehydration of the La, Pr, Nd, Sm and Eu complexes were determined.

---

Zusammenfassung Es wurde die thermische Zersetzung von Ln(NCS)₃(4-dipy)₂.5H₂O mitLn=La, Pr, Nd, Sm, Eu, Y und 4-dipy=4,4′-Dipyridyl untersucht. Die Verbindungen werden zuerst dehydratiert. Bei der thermischen Zersetzung von Ln(NCS)₃(4-dipy)₂ findet eine Desaminierung statt. Die übergangsprodukte zersetzen sich unter Bildung von Ln₂O₂SO₄. Die Aktivierungsenergie für den ersten Schritt der Dehydratation der La-, Pr-, Nd-, Sm- und Eu-Komplexe wurde ermittelt.

     

Complexes of Heavy Lanthanides and Yttrium with 3,4-dimethoxybenzoic Acid

The complexes of yttrium and heavy lanthanides with 3,4-dimethoxybenzoic acid of the formula: Ln(C₉ H₉ O₄ )₃ ×n H₂ O, where Ln =Y(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III) and Lu(III), and n =4 for Tb(III), Dy(III), n =3 for Ho(III), and n =0 for Er(III), Tm(III), Yb(III), Lu(III) and Y(III) have been prepared and characterized by elemental analysis, IR spectroscopy, thermogravimetric and magnetic studies and X-ray diffraction measurements. The complexes have colours typical of Ln³⁺ ions (Ho - cream, Tb, Dy, Yb, Lu, Y - white, Er - salmon). The carboxylate group in these complexes is a symmetrical, bidentate, chelating ligand. They are crystalline compounds characterized by various symmetry. On heating in air to 1273 K the hydrated 3,4-dimethoxybenzoates decompose in two steps while those of anhydrous only in one stage. The tetrahydrates of Tb and Dy and trihydrate of Ho 3,4-dimethoxybenzoates are firstly dehydrated to form anhydrous salts that next are decomposed to the oxides of the respective metals. The complexes of Er, Tm, Yb, Lu and Y are directly decomposed to the oxides of the appropriate elements. The solubility in water at 293 K for yttrium and heavy lanthanides is in the order of 10^-4 -10^-3 mol dm^-3 . The magnetic moments of the complexes were determined over the range 77–298 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and van Vleck. The results show that there is no influence of the ligand field on 4f electrons of lanthanide ions in these polycrystalline compounds and 4f electrons do not take part in the formation of M-O bonding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of rare earth element enanthates

The conditions of formation of Y, La and lanthanide (from Ce(III) to Lu) enanthates were worked out, their composition and their solubilities in water at 291 K were determined, and the conditions of their thermal decomposition were studied. They were prepared as crystalline solids with general formula Ln(C₇H₁₃O₂)₃·nH₂O, wheren=2–10. On heating, they decompose in two or three steps. They first lose some water molecules and then decompose to the oxides directly (salts of Y and heavy lanthanides) or via the intermediate formation of Ln₂O₂CO₃ (salts of La, Pr, Nd, Sm and Eu). Only yttrium enanthate dihydrate loses 2 water molecules on heating to form an anhydrous complex, which decomposes directly to Y₂O₃. The temperatures of dehydration are similar for all complexes (323–343 K), while the temperatures of oxide formation vary irregularly from 823 K for CeO₂ to 1078 K for La₂O₃.     

Comparison of thermal properties of lanthanide trimellitates prepared by different methods

By diffusion in gel medium new complexes of formulae: Nd(btc)⋅6H₂O, Gd(btc)⋅4.5H₂O and Er(btc)·5H2O (where btc=(C₆H₃(COO)₃ ³⁻) were obtained. Isomorphous compounds were crystallized in the form of globules. During heating in air atmosphere they lose stepwise water molecules and then anhydrous complexes decompose to oxides. Hydrothermally synthesized polycrystalline lanthanide trimellitates form two groups of isomorphous compounds. The light lanthanides form very stable compounds of the formula Ln(btc)⋅nH₂O (where Ln=Ce−Gd and n=0 for Ce; n=1 for Gd; n=1.5 for La, Pr, Nd; n=2 for Eu, Sm). They dehydrate above 250°C and then immediately decomposition process occurs. Heavy lanthanides form complexes of formula Ln(btc)⋅nH₂O (_Ln=Dy−Lu). For mostly complexes, dehydration occurs in one step forming stable in wide range temperature compounds. As the final products of thermal decomposition lanthanide oxides are formed.     

4,4′-Dipyridyl complexes of rare-earth thiocyanates

4,4-Dipyridyl complexes of rare-earth thiocyanates of the formulaLn(4-dipy)₂(NCS)₃·5H₂O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Y, 4-dipy = 4,4-dipyridyl) have been synthesized. The IR spectra of these compounds and other physical properties are discussed. The thermal decomposition of some compounds (in the order Gd ÷ Lu) has been investigated.

---

4,4-Dipyridylkomplexe von Seltenerdmetallthiocyanaten

Zusammenfassung Es wurden 4,4-Dipyridylkomplexe des TypesLn(4-dipy)₂(NCS)₃·5H₂O mitLn = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu und Y dargestellt. Die IR-Spektren und andere physikalische Eigenschaften werden diskutiert und die thermische Zersetzung von einigen Verbindungen (in der Reihe Gd ÷ Lu) untersucht.

     

Complexes of rare-earth metals with meconic acid

Two series of complexes of meconic acid (H₃ Mec) with rare-earths have been prepared by varying the preparative procedure. The compounds have the general formulae, [Ln(Mec) (H₂O)₂]·3 H₂O (whereLn=La, Ce, Pr, Nd, Sm, Ho and Y) and [Ln(HMec) (H₂ Mec) (H₂O)₂]·4 H₂O (whereLn=La, Pr, Nd and Sm). The infrared spectral data indicate that the carboxylate groups are bound to the rare-earth metal in a bidentate fashion. Thermal studies indicate that two water molecules are coordinated in each case. The complexes are probably polymeric.

---

Komplexe von Seltenerd-Metallen mit Meconsäure

Zusammenfassung Es wurden zwei Reihen von Komplexen der Meconsäure (H₃ Mec) mit Seltenerd-Metallen mit den allgemeinen Formeln [Ln(Mec)(H₂O)₂]·3 H₂O (Ln=La, Ce, Pr, Nd, Sm, Ho, Y) und [Ln(HMec)₂(H₂ Mec) (H₂O)₂]·4 H₂O (Ln=La, Pr, Nd, Sm) hergestellt. Die IR-Spektren zeigen, daß die Carboxylat-Gruppen in zweizähniger Weise mit den Metallionen koordinieren; thermische Untersuchungen ergeben, daß in beiden Reihen jeweils zwei Wassermoleküle zusätzlich koordiniert sind. Die Komplexe weisen wahrscheinlich eine Polymerstruktur auf.

     

Thermal and spectral properties of some anhydrous and hydrated rare earth hydrazinecarboxylates

The anhydrous rare earth hydrazinecarboxylates, Ln(N₂H₃COO)₃ where Ln=La, Ce, Pr, Nd or Sm and hydrated rare earth hydrazinecarboxylates, Ln(N₂H₃COO)₃(H₂O)₃ where Ln=La or Nd have been prepared and characterized by chemical analyses, infrared spectroscopy and thermal analyses (TG/DTA/DTG). The infrared spectra indicate that the hydrazinecarboxylate group in both the sets of complexes is coordinated in a bidentate (chelate) fashion with the N-N stretching frequency at 980-1000 cm^-1. The thermal analyses of all the complexes show multi-step decomposition. The final product in all the cases is invariably the respective metal oxide carbide, Ln₂O₂C₂, though there are some variations in the decomposition pattern. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal and spectral studies of rare earth element 3-methoxy-4-methylbenzonates

3-Methoxy-4-methylbenzoates of Y(III) and lanthanide(III) (La-Lu) were prepared as crystalline compounds with molar ratio of metal to organic ligand of 1.0:3.0 and general formula Ln(C₉H₉O₃)3·nH₂O, where n=2 for Y, La-Er and n=0 for Tm-Lu. IR spectra of the prepared complexes suggest that carboxylate groups are bidentate chelating. During heating dihydrated complexes lose crystallization water molecules in one (Y, La, Pr-Er) or two steps (Ce) and then all the anhydrous complexes decompose directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇.Vadim Mamleev is grateful to Region Nord-pas-de-Calais (France) for financial support and to laboratory PERF of ENSCL for its kind invitation to continue the joint work on thermal analysis.     

希土配合物的研究——Ⅷ.1, 4-双(1''-苯基-3''-甲基-5''-氧代吡唑酮基-4'')代-1, 4-丁二酮(BPMPBD)与希土元素配合物的合成及表征

在乙醇-水溶液中,当pH=5-6时,用希土硝酸盐与BPMPBD反应,合成了15种希土元素(除Sc、Pm外)的二元配合物.通过化学分析和元素分析确定了配合物的组成为REL₂·nH₂O(RE=La,n=5,RE=Y,n=4,RE=Pr、Nd、Sm、Eu、Gd,n=3),RE₂L₃·5H₂O(RE=Tb、Dy、Ho、Er、Tm、Yb、Lu)及CeL₂·4H₂O.研究了这些配合物的一些性质及红外光谱、紫外光谱、核磁共振、荧光光谱和差热分析,认为重希土配合物具有双核结构.     

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III)

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III) were obtained as mono-, di-, tri-or tetrahydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Er, n=2 for Ln=Tb, Dy, Tm, Y, n=3 for Ln=Ho and n=4 for Yb and Lu. The complexes were characterized by elemental analysis, FTIR spectra, TG, DTA and DSC curves, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate chelating ligand. All complexes are polycrystalline compounds. The values of enthalpy, ΔH, of the dehydration process for analysed complexes were also determined. The solubilities of heavy lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁴ mol dm⁻³. The magnetic moments were determined over the range of 76–303 K. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Thermal properties of lanthanide(III) complexes with 5-amino-1,3-benzenedicarboxylic acid

The complexes of yttrium(III) and lanthanides(III) with 5-amino-1,3-benzenedicarboxylic acid form two isostructural series of compounds and have the general formula Ln₂(C₈H₅O₄N)₃·nH₂O, where n = 13 for Y, La-Er and n=9 for Tm, Yb, Lu. They are insoluble in water and stable at room temperature. On heating in air or inert gas atmosphere they lose all water molecules in several steps. The anhydrous compounds are stable to about 400°C and next decompose to oxides.