Thermal decomposition of scandium(III) o-nitrobenzoate,o-chlorobenzoate,o-methylbenzoate,o-hydroxybenzoate and o-aminobenzoate in air atmosphere

The conditions of thermal decomposition of scandium o-nitrobenzoate, o-chlorobenzoate, o-methylbenzoate, o-hydroxybenzoate and o-aminobenzoate were studied. On heating, the carboxylates decompose in two steps, only scandium anthranilate decomposes in one step. The hydrated complexes first lose water of crystallization and then are transformed to Sc₂O₃. The dehydration of the complexes is an endothermic process and the decomposition of anhydrous complexes is strongly exothermic. Scandium o-nitrobenzoate decomposes explosively.     

Thermal decomposition of scandium(III) 2-chloro-, 30chloro, 4-chloro- and 2,4-dichlorobenzoates in an air atmosphere

The conditions of thermal decomposition of hydrated scandium(III) chlorobenzoates were studied. On heating, the carboxylates decompose in many steps. The hydrated complexes first lose water of crystallization in one or two steps and then anhydrous compounds are transformed to Sc₂O₃ with formation of Sc₂O(CO₃)₂ intermediate. The dehydration of the complexes is accompanied by an endothermic effect and the decomposition of anhydrous complexes by strong endothermic effects. The anhydrous complexes are melted at 255–300°C.     

Thermal decomposition of scandium(III) benzenetricarboxylates in air and nitrogen atmospheres

The conditions of thermal decomposition of scandium(III) hemimellitate, trimellitate and trimezinate in air and nitrogen atmospheres have been studied. On heating, the benzene-tricarboxylates of Sc(III) decompose in two stages. First, the hydrated complexes lose crystallization water; heating in air finally yields Sc₂O₃, and heating in a nitrogen atmosphere Sc₂O₃ and C. The dehydration of the complexes is associated with strong endothermic effects. The decomposition of benzenetricarboxylates in air is accompanied by an exothermic effect and in nitrogen by an endothermic effect. The activation energies of the dehydration and decomposition reactions have been calculated for the Sc(III) benzenetricarboxylates.     

Extraction of scandium(III) by bis(diphenylphosphorylmethylcarbamoyl)alkanes

The extraction of trace amounts of scandium(III) from HCl,HNO₃, and HClO₄ solutions in the form of complexes with neutral polyfunctional organophosphorus compounds bis(diphenylphosphorylmethylcarbamoyl)alkanes [Ph₂P(O)CH₂C(O)NH]₂(CH₂) _n (n = 3, 5, 8) was studied. The effect of the structure of the extractant, the aqueous phase composition, and the nature of the organic solvent on the efficiency of transition of scandium(III) ions into the organic phase was considered, and the stoichiometry of the extracted complexes was determined. The studied ligands exhibit a higher extraction power toward scandium(III) ions than their analog Ph₂P(O)CH₂C(O)NHC₉H₁₉ containing only one bidentate carbamoylmethylphosphoryl moiety per molecule. Scandium(III) passes into the organic phase most efficiently in the presence of HClO4 in the aqueous phase. It was shown that scandium(III) can be selectively recovered and preconcentrated by a complexing adsorbent obtained by noncovalent immobilization of bis(diphenylphosphorylmethylcarbamoyl)pentane on a macroporous polymer matrix.     

Solid state decomposition studies on metal salicylates. Thermal decomposition of some lanthanide salicylato complexes

The thermal stability and mechanism of thermal decomposition in air of the four lanthanide complexes of 2-hydroxybenzoic acid have been studied by TG, DSC, IR and MS techniques. An analysis of the prepared compounds show that Pr(III), Nd(III) and Tb(III) form anhydrous salicylato (Hsal)⁻ complexes while the corresponding holmium compound contains four water molecules. The TG curves show two (praseodymium, terbium), three (neodymium) or four (holmium) main stages of thermal decomposition. The most unstable among the complexes studied is Ho(Hsal)₃·4H₂O which releases four water molecules in an endothermic dehydration step. Ligand molecules decompose mainly in two stages of which the first is endothermic and is attributed to the release of the ligand acid and the second is a strongly exothermic decarboxylation process. The final decomposition product is the corresponding lanthanide(III) oxide, except in the case of terbium which decomposes to Tb₄O₇.     

Dimeric scandium(III) and monomeric lanthanide(III) complexes with perfluoropropane-1,3-disulfonates as counter anions for Lewis acid catalysis

A novel scandium(III) complex with disulfonates as counter anions, [Sc(μ-OH)(H₂O)₅]₂[O₃S(CF₂)₃SO₃]₂ (5), was prepared from scandium oxides (Sc₂O₃) and perfluoropropane-1,3-disulfonic acid (1, HO₃SCF₂CF₂CF₂SO₃H). By X-ray analysis, 5 was found to be a μ-OH-bridged dimeric structure bearing two perfluoropropane-1,3-disulfonates without bonding to scandium(III) centers. A series of lanthanide(III) complexes were also prepared from 1 and lanthanide oxides (Ln₂O₃; Ln = La, Nd, Sm, and Gd). In sharp contrast to the dimeric scandium(III) complex, the corresponding lanthanide(III) complexes had monomeric structures. Interestingly, the dimeric scandium(III) complex, but not the monomeric lanthanide complexes, with perfluoropropane-1,3-disulfonates served as an efficient Lewis acid catalyst for the hydrolysis of esters.     

Thermal decompositions of heavy lanthanide aconitates

The conditions of thermal decomposition of Tb(III), Dy, Ho, Er, Tm, Yb and Lu aconitates have been studied. On heating, the aconitates of heavy lanthanides lose crystallization water to yield anhydrous salts, which are then transformed into oxides. The aconitate of Tb(III) decomposes in two stages. First, the complex undergoes dehydration to form the anhydrous salt, which next decomposes directly to Tb₄O₇. The aconitates of Dy, Ho, Er, Tm, Yb and Lu decompose in three stages. On heating, the hydrated complexes lose crystallization water, yielding the anhydrous complexes; these subsequently decompose to Ln₂O₃ with intermediate formation of Ln₂O₂CO₃.     

Synthesis,characterization, and crystal structures of iodides and polyiodides of scandium complexes with urea and acetamide

Iodides and polyiodides of scandium complexes containing urea (Ur) and acetamide (AA) have been synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray diffraction. The trigonal crystals of [Sc(L)₆]I₃ (L?=?Ur, AA) and monoclinic crystals of [Sc(Ur)₆][I₃]₃ are isomorphous to the earlier reported [M(Ur)₆]I₃ (M?=?Ti, V, Cr, Fe) and [Ln(Ur)₆][I₃]₃ (Ln?=?Yb, Lu), respectively. Therefore, scandium in its complexes with urea and iodine links rows of 3d transition elements and rare-earth elements; it continues the tendency of formation of polyiodides with different structures from isomorphous iodides, which was found for other metal(III) urea complexes. In the orthorhombic crystals of [Sc(AA)₆][I₅][I₃]I, the first example of the M(III) acetamide polyiodide, metal ions in complex cations are located at the centers of distorted octahedral arrangements of oxygen atoms of acetamide; iodide ions are not coordinated. The crystals of [Sc(AA)₆][I₅][I₃]I contain V-shaped pentaiodide, linear triiodide, and isolated iodide anions.     

Reduced Arene Complexes of Scandium

Alkali metal naphthalenide or anthracenide reacted with scandium(III) anilides [Sc(X){N(tBu)Xy}₂(thf)] (X=N(tBu)Xy ( 1 ); X=Cl ( 2 ); Xy=C₆H₃-3,5-Me₂) to give scandium complexes [M(thf)_n][Sc{N(tBu)Xy}₂(RA)] (M=Li–K; n=1–6; RA=C₁₀H₈²⁻ ( 3-Naph-K ) and C₁₄H₁₀²⁻ ( 3-Anth-M )) containing a reduced arene ligand. Single-crystal X-ray diffraction revealed the scandium(III) center bonded to the naphthalene dianion in a σ²:π-coordination mode, whereas the anthracene dianion is symmetrically attached to the scandium(III) center in a σ²-fashion. All compounds have been characterized by multinuclear, including ⁴⁵Sc NMR spectroscopy. Quantum chemical calculations of these intensely colored arene complexes confirm scandium to be in the oxidation state +3. The intense absorptions observed in the UV/Vis spectra are due to ligand-to-metal charge transfers. Whereas nitriles underwent C−C coupling reaction with the reduced arene ligand, the reaction with one equivalent of [NEt₃H][BPh₄] led to the mono-protonation of the reduced arene ligand.     

Thermal decompositions of scandium(III) 2,4-dinitrobenzoate, 3,5-dinitrobenzoate, 2,4-dichlorobenzoate and 3,4-diaminobenzoate in air atmosphere

The thermal decompositions of scandium 2,4-dinitrobenzoate, 3,5-dinitrobenzoate, 2,4-dichlorobenzoate and 3,4-diaminobenzoate were studied. On heating, the carboxylates decompose in two steps. The hydrated complexes first lose crystallization water and are transformed to Sc₂O₃. The dehydration of the complexes is accompanied by an endothermic effect and decomposition of the anhydrous or monohydrate complezes by strong exothermic effects. Scandium 2,4-dinitrobenzoate and 3,5-dinitrobenzoate decompose explosively.     

Thermal decompositions of light lanthanide aconitates

The conditions of thermal decomposition of Y, La, Ce(III), Pr, Nd, Sm, and Gd aconitates have been studied. On heating, the aconitate of Ce(III) loses crystallization water to yield anhydrous salt, which then is transformed in to oxide CeO₂. The aconitates of Y, Pr, Nd, Sm, Eu and Gd decompose in three stages. First, aconitates undergo dehydration to form the anhydrous salts, which next decompose to Ln₂O₂CO₃. In the last one the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ is accompanied by endothermic effect. Dehydration of aconitate of La undergoes in two stages. The anhydrous complex decomposes to La₂O₂CO₃; this subsequently decomposes to La₂O₃.     

Synthesis,quantum chemical calculations,and luminescent properties of scandium,europium, gadolinium,and terbium 1-(2-pyridyl)naphtholate complexes

By reactions of 1-(2-pyridyl)naphth-2-ol (pynH) with silylamides Ln[N(SiMe₃)₂]₃ (Ln = Sc, Eu, Gd, or Tb), the Ln(pyn)₃ complexes of the metals have been synthesized. Only the scandium complex in a THF solution has displayed photoluminescence (band with a maximum at 455 nm and a halfwidth of 65 nm). Electroluminescent properties have been revealed for the scandium and terbium complexes. In an ITO/TPD/Sc(pyn)₃/Bath/Yb three-layer light emitting diode, the scandium complex exhibits yellow-green luminescence with a brightness of 4750 cd/m² at a voltage of 21 V. The terbium complex Tb(pyn)₃ in the same device has displayed a single, broad luminescence band with λ_max = 570 nm due to excimer emission. By density functional theory quantum chemical calculations, different structures of the complexes have been revealed, mononuclear for Sc(pyn)₃ and binuclear for Ln₂(pyn)₆. This difference in structure seems to be responsible for differences in electroluminescent activity between the synthesized complexes.     

Thermoanalytical studies of oxovanadium(IV)hydroxamate complexes

The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C₆H₅C(O)NHO)] (I), [VO(C₆H₅C(O)NHO)₂] (II), [VO(acac)(4-ClC₆H₄C(O)NHO)] (III), [VO(4-ClC₆H₄C(O)NHO)₂] (IV) (where acac = (CH₃COCHCOCH₃ ^–) synthesized from the reactions of VO(acac)₂ with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in single step to yield VO₂ as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO₂ as the ultimate product of decomposition. The formation of VO₂ has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability for the complexes has been inferred as IV > I > III > II.     

Spectral and thermal investigation of rare earth element 4-methoxy-2-methylbenzoates

4-Methoxy-2-methylbenzoates of Y(III) and lanthanides(III) (La-Lu) were prepared as crystalline anhydrous complexes with general formula Ln(C₉H₉O₃)₃ (complexes of La and Pr as monohydrates). Monohydrates heated in air lose crystallization water molecule and then anhydrous complexes decompose directly to oxides. Only La(III) complex decomposes to oxide with intermediate formation La₂O₂CO₃. The carboxylate group in the studied complexes is a tridentate chelating - bridging or bidentate chelating (Y). This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies on lanthanoid sulfites: Part VI. Thermogravimetric study of scandium sulfite pentahydrate

Scandium sulfite was found to crystallize as a pentahydrate both at 25 and 90 °C when precipitated by the action of sulfur dioxide on aqueous suspensions of Sc(OH)₃. Thermogravimetric analysis showed that the anhydrous sulfite is formed by 200 °C but it starts to decompose immediately after its formation. The decomposition leads to an intermediate phase which is stable up to 700 °C in inert (nitrogen) and air atmospheres but decomposes earlier in reductive (hydrogen) environment. The weight remaining, which corresponds to the intermediate level, varies between 58 and 43 %, depending on experimental conditions and thus cannot be assigned to a single compound such as Sc₂O₂SO₄ or Sc₂O₂SO₃. The intermediate phase is amorphous to X-rays but IR spectra indicate the presence of both sulfite and sulfate ions pointing to a mixture. In all atmospheres studied the final decomposition step is the formation of scandium sesquioxide.     

Complexes of d and f Metals with 2-Methyl-3-hydroxy(amino)pyrido[1,2-a]pyrimidine-4-one. Crystal Structure of 2-Methyl-3-hydroxypyrido[1,2-a]pyrimidine-4-one

Six complexes of scandium(III), lanthanum(III), praseodymium(III), and copper(II) chlorides with 2-methyl-3-hydroxypyrido[1,2-a]pyrimidine-4-one (HL¹) and 2-methyl-3-aminopyrido[1,2-a]pyrimidine-4-one (L²), as well as hydrochloride and hydronitrate L², were isolated. The crystal and molecular structures of HL¹ were determined. HL¹ in CCl₄ solution was shown (IR data) to occur as two forms, namely, neutral and zwitterionic forms. The structures for the complexes isolated were proposed.     

Heterogeneous reactions of solid nickel(II) complexes XXIV

The Stoichiometry of thermal decomposition was studied for the following compounds: Ni(NCS)₂(pip)₄ (I), (pip=piperidine), Ni(NCS)₂(pip)₂py·H₂O (II), (py=piridine), Ni(NCS)₂(4-Mepip)₃ (III), Ni(NCS)₂(3-Mepip)₃ (IV) and Ni(NCS)₂(3.5-Me₂pip)₃ (V). In complexes I, II, III and IV the loss of the volatile ligands (on the TG curve to 300 °C) occurs in three steps and in complex V in two steps. The loss of the last molecules of volatile ligands is accompanied by the decomposition of NCS groups. Spectral data and magnetic moment values for the initial complexes I and II (together with the defined intermediates) indicated pseudooctahedral configuration while pentacoordination for complexes III, IV and V. Structural changes of the complexes studied in thermal decomposition reactions are discussed.     

Thermal decomposition of potassium bis -oxalatodiaqua-indate(III) monohydrate

Indium (III) is precipitated with oxalic acid in the presence of potassium nitrate maintaining an overall concentration of 0·125 M in HNO₃. Chemical analysis of the complex salt obtained indicates the formula, K[In(C₂O₄)₂]·3H₂O. Thermal decomposition studies show that the compound decomposes first to the anhydrous potassium indium oxalate and then to the final mixture of the oxides through formation of potassium carbonate and indium (III) oxide as intermediates. Isothermal study, X-ray diffraction pattern and IR spectral data support the proposed thermal decomposition mechanism.     

Thermal analysis, decomposition kinetics, and molecular modeling of transition metal (Fe, Co) surfactant complexes

A detailed thermal analysis of iron and cobalt surfactant complexes of the type [M(CH₃COO)₄]^2?[C₁₂H₂₅NH₃ ⁺]₂ has been carried out using Thermogravimetric (TG) analysis at different heating rates (i.e., 5, 10, 15, and 20 °C min^?1). It has been observed that iron complex decomposes by a different mechanism compared to other transition metal complexes. Metal is the final product instead of metal oxide. Combining the results from our previous study, first row transition metal complexes exhibit an order of stability in agreement with the famous Irving Williams series, i.e., the apparent activation energy, E for thermal decomposition varies as: E _Fe > E _Co < E _Ni < E _Cu > E _Zn (exception being iron because of different decomposition mechanism). Thermal decomposition parameters have been measured and compared using the multiple heating rate method of Flynn–Wall–Ozawa. Further, molecular modeling calculations have been carried out to compare the experimental TG data with theoretical computations for the synthesized metal surfactant complexes. Minimum energy optimized structures for the complexes have been obtained using Gaussian software.     

Synthesis,molecular weights and infrared spectra of some scandium(III) higher carboxylates

Summary Anhydrous scandium(III)carboxylates of general composition SC(O₂CR)₃ (where R = C₁₁ H₂₃, C₁₃ H₂₇, C₁₅H₁₃, C₁₇H₃₅ and C₂₁ H₄₃) have been synthesized in aqueous solution. Hexacoordinated monomers are suggested on the basis of elemental analyses, molecular weights and i.r. spectra of the complexes.