Thermal analysis of some polynuclear coordination compounds

The thermal behaviour of five polynuclear coordination compounds containing tartaric anion as ligand, namely (NH₄)₃[LnFe(C₄O₆H₄)₃(OH)₃] (Ln=La and Eu), (NH₄)₂[PrFe(C₄O₆H₄)₃(OH)₂] and (NH₄)[LnFe(C₄O₆H₄)₃(OH)]·3H₂O (Ln=Nd and Gd) was investigated. The reaction progress was studied by TG/DTA and FTIR measurements. Oxalates and oxocarbonates were identified as intermediates. In the case of Ln=La, Nd, Pr, Eu and Gd, pure LnFeO₃ was obtained as final decomposition product. The thermal decomposition of Eu-Fe compound, leads to a mixture of mixed (ortho-ferrite (EuFeO₃) and garnet (Eu₃Fe₅O₁₂)) and simple oxides (Eu₂O₃ and α-Fe₂O₃).     

Lattice enthalpies and magnetic loops in lanthanide iron garnets,Ln3Fe5O12

Experimental lattice enthalpies Δ_LH^θ of lanthanide iron garnets Ln₃Fe₅O₁₂ (LnIGs) with Ln = Ce − Lu, have been determined from the Born–Haber thermochemical cycle. The results have been compared with those reported by other authors using numerical simulation or an empirical equation. The lattice enthalpy of PmIG has been predicted by linear interpolation between Δ_LH^θ of the adjacent NdIG and SmIG. It has been found that the partial derivative (∂Δ_LH^θ/∂V_m) for the series of LnIGs corresponds by magnitude and dimension to an upper limit of their rigidity. New effect of magnetic loops has been noted in the same series in the dependence of the lattice magnetic entropies on the effective magnetic moments (theoretical and experimental values).     

Thermal behaviour of some Al(III)-Mg(II) polynuclear coordination compounds with polycarboxylic acid anions as ligands,precursors of aluminates

A TG, DTG and DTA study of three polynuclear coordination compounds,containing Al(III)-Mg(II), namely (NH₄)₄[Al₂Mg(C₄O₅H₄)₄(OH)₄]?2H₂O,(NH₄)₄[MgAl₂(C₄H₄O₆)₄(OH)₄]?3H₂Oand (NH₄)₂[Al₂Mg(C₆O₇H₁₁)₅(OH)₅]?3H₂O,has been reported together with the associated thermal decomposition mechanismrationalized in terms of intermediate products. As decomposition end-product,magnesium-aluminum spinel is obtained. The values of MgAl₂O₄mean crystallite size depend on the anionic ligand contained by the precursorcompound, varying in the order: malate (143 Å) ligand contained by theprecursor compound, varying in the order: malate (143 Å)     

Incorporation of trivalent cations in synthetic garnets A3B5O12 (A = Y, Lu-La, B = Al, Fe, Ga)

Static-lattice atomistic calculations have been used to study the solution energy for the incorporation of 13 foreign cations at 3 different lattice positions of 12 synthetic garnets. Trends have been obtained as a function of the ionic radius of the dopant cation, and the predictions about site preference have been compared with both literature and experimental data. The preferred substitution site is mainly determined by the ionic size and has been correctly predicted in all cases. Moreover, the energy difference between the preferred substitution site and the next favored site is relatively small in several cases, and hence the foreign ions can be inserted at two different positions by using the correct stoichiometry. A remarkably different behavior has been encountered for Al garnets, due to the smaller size of the unit cell. In particular, some cations, such as Fe3+ and Ga3+, can be inserted at the dodecahedral position usually occupied by the rare-earth ion. Despite the limitations of the static-lattice approach, the results of the present simulations help in the understanding of the defect chemistry of garnets, which is strongly responsible for the physicochemical properties (such as luminescence and ferrimagnetism) that make garnets interesting for technological applications. Such results lead to the possibility of tuning the optical and luminescence properties of garnets by the formation of different types of solid solutions.     

Addition of CCl4 to unsaturated compounds catalyzed by M3(CO)12 (M=Fe, Ru, Os)

The addition of CCl₄ to hex-1-ene and to the methyl ester ofN-(trans-cinnamoyl)-l-proline (2) catalyzed by M₃(CO)₁₂ or by the M₃(CO)₁₂+DMF system (M=Fe, Ru, Os) was studied. The use of ruthenium and osmium dodecacarbonyls in combination with DMF increases the yields of adducts CCl₃CH₂CHClC₄H₉ (4) and PhCHClCH(CCl₃)C(O)R′ (3) over those obtained in reactions catalyzed by the same carbonyls without DMF. In addition to adduct3, salts [M(CO₃)Cl₃]⁻[Me₂NH₂]⁺ were isolated from the products of the reaction between CCl₄ and1 in the presence of M₃(CO)₁₂+DMF (M=Ru, Os). These salts do not catalyze this reaction and apparently result from chain termination. Experimental results in favor of a coordination mechanism of the addition of CCl₄ to olefins in the presence of Ru₃(CO)₁₂ and Os₃(CO)₁₂ were obtained. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 6, pp. 1174–1179, June, 1997.     

Synthesis,characterization, and thermal properties of silicon(IV) compounds containing amidinate ligands as CVD precursors

The title compounds of the type R-C(=NⁱPr) (-N′ ⁱPrSiMe₃) (with R = Me or ⁿBu) as potential chemical vapor deposition (CVD) precursors have been synthesized and characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy as well as by EI-MS and elemental analysis where necessary. Thermal properties, including stability, volatility, transport behavior, and vapor pressure, were evaluated by thermogravimetric analysis to confirm that they are suitable for the CVD procedure. Deposition was accomplished in a hot wall CVD reactor system, which qualitatively verified the ability of these compounds as CVD precursors.     

异核高氯酸钐、镝在二苯亚砜体系中的共发光

合成了一系列异核高氯酸钐、镝二苯亚砜配合物：SmxDy1-x(DPSO)7(ClO4)(x=1.000-0.000,DPSO为二苯亚砜）。测定了配合物的组成、IR谱、荧光激发和发射光谱。荧光发射光谱表明：在二苯亚砜体系中Sm^3 对Dy^3 的发光有明显的猝灭作用，而Dy^3 对Sm^3 的发光有较强的敏化作用。根据配合物的荧光光谱计算了（Sm^3 、Dy^3 )及配体DPSO的有关能级，并研究了猝灭和敏化的机理。     

Synthesis and X-ray diffraction study of Tm M 3 II Fe5O12 (MII = Ca, Sr, Ba) compounds

Double ferrites were synthesized by solid-phase annealing from thulium and iron oxides and alkaline-earth carbonates for the first time. Their symmetry systems and unit cell parameters were determined by X-ray diffraction analysis.     

羰基原子簇化合物M3(CO)12(M=Fe,Ru,Os)的激光解离研究

在自制的仪器上以冲激光溅射铁、钌、锇的三核羰基原子簇化合物。由原位质谱观察和分析溅射产生的正负离子。比较了解离碎片及分布发现羰基锇原子簇化合物具有特殊的结构稳定性。它们不仅具有很强的金属键,而且锇与羰基分子还形成了很强的配位键。     

Synthesis,Characterization and Thermal Decompositions Studies of Some Malates Coordination CompoundsI. iron nickel compounds

The thermal behaviour of three coordination compounds, potential precursors of nickel ferrite [Fe₂Ni(C₄H₄O₅)_2.5(OH)₂]NO₃·5H₂O,[Fe₂Ni(C₄H₈O₃N₂)₄](NO₃)₈·24H₂O and (NH₄)[Fe₂Ni(C₄H₄O₅)₃(OH)₃]·3H₂O has been investigated to evaluate their suitability as precursors for nickel ferrite. For a complete and reliable assignment of the thermal transformations, the isolable solid intermediates and end products were characterized by IR, X-ray diffraction and Mössbauer investigations. A decomposition scheme is proposed.     

Thermal Decompositions of (RE)Ba2Cu3O6 (RE=Y,Nd, Er)

Thermogravimetric in situ measurements of oxygen loss from (RE)Ba₂Cu₃O₆ samples (RE=Y, Nd, Er) heated isothermally in a relatively high dynamic vacuum were made with a Cahn RG electrobalance. Single-phase orthorhombic samples of composition (RE)Ba₂Cu₃O_7-x (highest oxygen content) were synthesized from stoichiometric (1:2:3) mixtures of high-purity (RE)₂O₃, BaCO₃ and CuO. The original 1:2:3 mixture was prepared by the two-stage procedure described earlier. The crystal structure of the sample in the original orthorhombic phase was controlled by the X-ray powder method (CuKα radiation) using a Stadi P Stoe diffractometer with a position-sensitive detector. The decomposition curves are described by the sum of exponential terms corresponding to rapid and slow first-order processes in which differently sized grains of the powder samples are involved. The activation energies are estimated from appropriate Arrhenius plots. This revised version was published online in July 2006 with corrections to the Cover Date.     

Crystal Structure of [M(NH3)5Cl]2[IrCl6]Cl2 (M = Co, Rh, Ir) Binary Complex Salts

Binary complex salts of M(NH₃)₅Cl]₂[IrCl₆]Cl₂ composition, where M = Co(III), Rh(III), or Ir(III), have been studied. All phases are isostructural with [M(NH₃)₅Cl]₂[PtCl₆]Cl₂ complexes [M = Rh(III) and Ir(III)]; Xray structural and crystallochemical analysis have been performed.     

Chiral molecular magnets: synthesis, structure, and magnetic behavior of the series [M(L-tart)] (M = Mn(II), Fe(II), Co(II), Ni(II); L-tart = (2R,3R)-(+)-tartrate)

A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramagnetic metal centers form pseudotetragonal layers in which each metal is surrounded by four other metals, with syn,anti carboxylate bridges. These salts show intralayer antiferromagnetic or ferromagnetic interactions, depending on the electronic configuration of the metal, and weak interlayer antiferromagnetic interaction. In all cases the magnetic properties are strongly affected by the anisotropy of the system, and the presence of magnetic canting has been found. The Mn derivative behaves as a weak ferromagnet with a critical temperature of 3.3 K. The Ni derivative shows very unusual magnetic behavior in that it exhibits antiferromagnetic ordering below 6 K, the onset of spontaneous magnetization arising from spin reorientation into a canted phase below 4.5 K, and a field-induced ferromagnetic state above 0.3 T at 2 K, behavior typical of metamagnets. The Fe and Co derivatives show antiferromagnetic interactions between spin carriers, but do not order above 2 K.     

Synthesis, Characterization and Thermal Decomposition of M1[M2(C2O4)2]xH2O (x=5 for M1=Co and x=4 for M1=Cd; M2=Ni)

Cobalt bis(oxalato)nickelate pentahydrate, Co[Ni(C₂O₄)₂]5H₂O and cadmium bis(oxalato)nickelate tetrahydrate, Cd[Ni(C₂O₄)2]4H₂O have been synthesized and characterized by elemental analysis, reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA ) in air showed that both the compound of cobalt and cadmium produced the oxide, MNiO_x (x=3 for M=Co; x=2 for M=Cd ) at 325 and 360°C respectively. DSC studies in nitrogen attributed only the mixture of both the metal at the end. This revised version was published online in July 2006 with corrections to the Cover Date.     

The preparation of WMeCl3Y (Y = S OR Se) and some coordination compounds of WMeCl3Y (Y = O,S OR Se)

The reaction of WCl₄Y (Y = S or Se) with Me₂Mg leads to the formation of WMeCl₃Y. The compounds WMeCl₃Y (Y = O, S or Se) are very reactive and attempts to isolate them in pure form failed. However, a range of complexes which they form with some nitrogen and oxygen donors have been isolated and characterised.     

[M3V18O42(H2O)12(XO4)]⋅24 H2O (M=Fe,Co; X=V,S): Metal Oxide Based Framework Materials Composed of Polyoxovanadate Clusters

New framework materials composed of well-defined vanadium oxide clusters were prepared by low-temperature reactions and characterized by X-ray crystal structure analysis. The structures of these solids contain {V₁₈O₄₂} cages linked into two interpenetrating three-dimensional networks by bridging {M(H₂O)₄} groups (M=Fe^II, Co^II; see picture).     

Magnetism of cyano-bridged Ln3+-M3+ complexes. Part II: one-dimensional complexes (Ln3+ = Eu, Tb, Dy, Ho, Er, Tm; M3+ = Fe or Co) with bpy as blocking ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to 13 one-dimensional complexes: trans-[M(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.4nH2O.1.5nbpy (Ln = Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Lu3+; M = Fe3+, Co3+). The structures for [EuFe]n (1), [TbFe]n (2), [DyFe]n (3), [HoFe]n (4), [ErFe]n (5), [TmFe]n (6), [LuFe]n (7), [EuCo]n (8), [TbCo]n (9), [DyCo]n (10), [HoCo]n (11), [ErCo]n (12), and [TmCo]n (13) have been solved: they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular architecture created by the interplay of coordinative, hydrogen bonding, and pi-pi interactions. A stereochemical study of the eight-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. The Ln3+-Fe3+ interaction is antiferromagnetic in [DyFe]n and [TbFe]n. For [EuFe]n, [HoFe]n, [ErFe]n, and [TmFe]n, there is no sign of any significant interaction. The magnetic behavior of [DyFe]n suggests the onset of weak long-range ferromagnetic ordering at 2.5 K.     

Kinetics and Mechanism of the Thermal Decomposition of M(NO3)2·nH2O (M=Cu,Co, Ni)

This paper presents the results of simultaneous DTA-TG-DTG and DSC studies on the thermal decomposition of Cu(NO3)2·3H2O, Co(NO3)2·6H2O and Ni(NO3)2·6H2O in an air atmosphere. The mechanism and enthalpies of the investigated processes were determined, as well as the kinetic parameters of the processes run under non-isothermal conditions by means of Kissinger's method. The dependence of the activation energy on the ionic radius of the cations building up the crystal lattices of the investigated compounds was also studied. This revised version was published online in July 2006 with corrections to the Cover Date.