Hexachloroantimonate(V) mit Nitroderivaten als Liganden, 3. Mitt.: Komplexe Verbindungen mit dreiwertigen Metallen

Complex compounds of trivalent metal chlorides (AlCl₃, CrCl₃, FeCl₃) are described, which had been obtained in a double complexation reaction in CCl₄ as a solvent with nitro compounds and SbCl₅:M ^III(C₆H₅NO₂) _m (SbCl₆)₃ (m=3,6),M ₂ ^III(C₆H₅NO₂)₄(SbCl₆)₄ and Al(-C₁₀H₇NO₂)₃(SbCl₆)₃. Synthesis, analytical results and i.r. spectra are discussed.     

Synthesis and characterization of complexes of the first transition series cations with 2,2′-biimidazole and 2,2′-biimidazolate

Mononuclear [M(hfacac)₂(H₂biim)] complexes, where M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II or Zn^II, hfacac = hexafluoroacetylacetonate, H₂biim = 2,2-biimidazole; dinuclear K₂[M₂(acac)₄(-biim)] (M = Cu^II or Zn^II) and tetranuclear K₂[M₄(acac)₈( ₄-biim)] (M = Co^II or Ni^II) complexes have been prepared and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r. spectroscopies and by magnetic susceptibility measurements (in the 2–300 K range). Mn^II, Fe^II and Co^II are in a high spin state. The e.p.r. spectra of Cu^II and Mn^II compounds have been recorded.     

Complexes of 2-(2-hydroxyacetophenone)imino-5-(p-anisyl)-1,3,4-oxadiazole with some bivalent metals ions

Summary The metal complexes of the type [M(SB)₂(H₂O)₂] and [M(SB)₂][where M = Mn^II, Co^II, Ni^II or Cu^II, M = Zn^II Cd^II, Hg^II and Pb^II and SBH = 2-(2-hydroxyacetophenone)imino-5-(p-anisyl)-1,3,4-oxadiazole] have been prepared and characterised by elemental analyses, thermal analyses, magnetic measurements, electronic and infrared spectral studies. The complexes [M(SB)₂(H₂O)₂] possess octahedral structures, whereas complexes [M(SB)₂] are tetrahedral. The crystal field parameters of the Co^II and Ni^II complexes are also calculated.     

Thermal expansion in 3d-metal Prussian Blue Analogs—A survey study

We present a comprehensive study of the structural properties and the thermal expansion behavior of 17 different Prussian Blue Analogs (PBAs) with compositions M^II₃[(M′)^III(CN)₆]₂·nH₂O and M^II₂[Fe^II(CN)₆]·nH₂O, where M^II=Mn, Fe, Co, Ni, Cu and Zn, (M′)^III=Co, Fe and n is the number of water molecules, which range from 5 to 18 for these compounds. The PBAs were synthesized via standard chemical precipitation methods, and temperature-dependent X-ray diffraction studies were performed in the temperature range between −150 °C (123 K) and room-temperature. The vast majority of the studied PBAs were found to crystallize in cubic structures of space groups Fm3?m, F4?3m and Pm3?m. The temperature dependence of the lattice parameters was taken to compute an average coefficient of linear thermal expansion in the studied temperature range. Of the 17 compounds, 9 display negative values for the average coefficient of linear thermal expansion, which can be as large as 39.7×¹0⁻⁶ K⁻¹ for Co₃[Co(CN)₆]₂·12H₂O. All of the M^II₃[Co^III(CN)₆]₂·nH₂O compounds show negative thermal expansion behavior, which correlates with the Irving–Williams series for metal complex stability. The thermal expansion behavior for the PBAs of the M^II₃[Fe^III(CN)₆]₂·nH₂O family are found to switch between positive (for M=Mn, Co, Ni) and negative (M=Cu, Zn) behavior, depending on the choice of the metal cation (M). On the other hand, all of the M^II₂[Fe^II(CN)₆]·nH₂O compounds show positive thermal expansion behavior.     

Synthesis and crystal structures of [UO2(C6H4NO2)2(C6H5NO2)] and [UO2SO4(C6H5NO2)(H2O)] · H2O

The complexes [UO₂(C₆H₄NO₂)₂(C₆H₅NO₂) (I) and [UO₂SO₄(C₆H₅NO₂)(H₂O)] · H₂O (II) were synthesized and studied by X-ray diffraction analysis. Crystals I are monoclinic: a = 7.0081(3), b = 14.9624(7), c = 9.1837(5) ?, β = 96.594(2)°, Z = 2, space group P2₁/m. Crystals II are triclinic: a = 6.8097(6), b = 9.3837(8), c = 10.4556(10) ?, α = 85.279(3), β = 75.434(3), γ = 69.180(3)°, Z = 2, space group . The main structural unit of crystal I is a mononuclear fragment, which belongs to the crystal chemical group AB ₂ ⁰¹ M¹ (A = UO ₂ ²⁺ , B⁰¹ are ions of pyridine-2-carboxylic (picolinic) acid, M¹ are molecules of picolinic acid) of the uranyl complexes. The main structural unit of crystal II is a chain, which belongs to the crystal chemical group AT³M ₂ ¹ (where T³-SO ₄ ²⁻ , M¹ are water and picolinic acid molecules) of the uranyl complexes. Picolinic acid in complexes I, II was found to have a zwitterion structure. Original Russian Text ? E.V. Grechishnikova, E.V. Peresypkina, A.V. Virovets, Yu.N. Mikhailov, L.B. Serezhkina, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 6, pp. 468–475.     

Mixed metal complexes in solution. Thermodynamic and spectrophotometric study of copper(II)-citrate heterobinuclear complexes with nickel(II), zinc(II) or cadmium(II) in aqueous solution

Summary A thermodynamic study of Cu^II–M^II-citrate (M^II=Ni^II, Zn^II or Cd^II) ternary systems has been performed by means of potentiometric measurements of hydrogen ion concentration at different temperatures (10, 25, 35 and 45°C) and at I=0.1 mol dm^–3 (KNO₃).The different binary and ternary systems involved have been further characterized by visible spectra and by calculating the spectra ( versus ) of all the Cu^II complexes.The thermodynamic data suggest strong entropic stabilization for the species under discussion. As regards the visible spectral characteristics of Cu^II(d-d transitions), the substitution of one Cu^II ion in the dimer [Cu₂(cit)₂H_–2]^4– by Ni^II or Zn^II to form heterobinuclear [CuM(cit)₂H_–2]^4– complexes, gives rise to a change in the visible spectrum.     

Ethers as ligands. Part V(1). Metal(II)-diglyme and -pentaglyme solvates

Summary Eighteen new coordination compounds are reported with diglyme (dgm) and pentaglyme (pgm) as ligands:viz. [M(dgm)₂](SbCl₆)₂ with M=Mg^II, Ca^II, Sr^II, Mn^II, Fe^II, Co^II, Ni^II, Cu^II, and Zn^II; [M(pgm)](SbCl₆)₂ with M=Mn^II, Fe^II,Co^II, Ni^II, Cu^II, and Zn^II; and [M(pgm)](SbCl₆)₂ · H₂O with M=Mg^II, Ca^II, and Sr^II. The metal(II) ions are hexacoordinated by the ether-oxygens of two diglyme molecules or of one pentaglyme molecule. The coordinated diglyme molecules are in the TGTT¯GT conformation.     

Preparation and structure of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 3-amino-5-(α/β)pyridyl-1, 2, 4-triazoles

Summary Complexes of bidentate 3-amino-5-()-pyridyl-1,2,4-triazole (L¹) and 3-amino-5-()-pyridyl-1, 2, 4-triazole (L²) of composition [ML¹Cl₂·H₂O], [ML²Cl₂·H₂O], [ML ₃ ^2/1 Cl₂] and [ML ₃ ^2/2 Cl₂] [M=Co^II, Ni^II, Cu^II, M=Zn^II] have been prepared and characterized by elemental analyses, i.r., u.v./visible, e.s.r. spectra, magnetic moments and molar conductances.     

Crystal structure and spectra of the Ni(II) complex of pyridine-2,6-dithio-carbomethylamide

The crystal structure of the paramagnetic bis(pyridine-2,6-dithiocarbomethylamide) nickel(II) nitrate (NiPDTA) is described: C₁₈H₂₂N₆S₄·(NO₃)₂·(H₂O)_1,5, monoclinic, C2/c,Z=4,a=14.705 (3) Å,b=23.254 (8) Å,c=8.383 (3) A, =98.18 (2)°,d _x=1.55 gcm^–3,d _m=1.53 gcm^–3. The structure was solved withPatterson and differenceFourier techniques and refined to a residual ofR=0.053. The nickel is surrounded by a square bipyramidal coordination of four thioamide sulfur atoms and two pyridine nitrogen atoms. Vibrational and electronic band positions for this compound are discussed.

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Kristallstruktur und Spektren des Pyridin-2,6-dithiocarbomethylamid Nickel(II)-Komplexes

Zusammenfassung Die Kristallstruktur des paramagnetischen bis(Pyridin-2,6-dithiocarbomethylamid) Nickel(II)-nitrats (NiPDTA) wurde bestimmt. C₁₈H₂₂N₆S₄Ni·(NO₃)₂·(H₂O)_1,5, monoklin, C2/c,Z=4,a=14,705 (3) Å,b=23,254 (8) Å,c=8,383 (3) A, =98,18 (2)°,d _x=1,55gcm^–3,d _m=1,53gcm^–3. Das Phasenproblem wurde mittelsPatterson-und Differenz-Fourier-Synthese bestimmt und die Struktur bis zu einem kristallographischenR-Faktor vonR=0.053 verfeinert. Das Nickel-Atom ist von vier Thioamid-Schwefelatomen und zwei Pyridin-Stickstoffatomen in quadratisch-bipyramidaler Anordnung umgeben. Schwingungsspektren und Anregungsspektren des Komplexes werden diskutiert.

     

Synthesis, structures, and thermolysis of new heterometallic cobalt, nickel, and copper complexes with the [Ru(NO)(NO2)4(OH)]2− anion as a ligand

Heterometallic complexes with pyridine-N-oxide (PyO), Ru(NO)(NO₂)₄(OH)Ni(PyO)₂(H₂O)] · CH₃COCH₃ (I), [{Ru(NO)(NO₂)₂(μ-NO₂)₂(μ-OH)Co}₂(μ-PyO)] · H₂O · CH₃COCH (II), and [Ru(NO)(NO₂)₄(OH)Cu(PyO)₂ (III), are isolated in the reactions of Na₂[Ru(NO)(NO₂)₄(OH)] with nitrates of the corresponding metals in the presence of the organic ligand. The compounds synthesized are characterized by IR spectra, thermal analysis, and X-ray diffraction analysis. Depending on the M²⁺ cation, the ruthenium cation is coordinated through the bidentate (III, Cu²⁺) or tridentate (I, Ni²⁺ and II, CO₂₊) mode involving the bridging OH group and one or two NO₂ groups. The thermal decomposition of complex II results in the formation of a Co_0.5Ru_0.5 solid solution, which is thermodynamically stable under the decomposition conditions. The thermolysis of complexes I and III in a hydrogen atmosphere leads to the formation of metastable solid solutions.     

Synthesis and Physicochemical Study of Iron(II), Cobalt(II), Nickel(II), and Copper(II) Complexes with 4-(2-Pyridyl)-1,2,4-Triazole

New complexes of iron(II), cobalt(II), and nickel(II) with 4-(2-pyridyl)-1,2,4-triazole (PyTrz), [Fe₃(PyTrz)₈(H₂O)₄]A₆ (A = NO₃ ^-, ClO₄ ^-, Br^-) and [M₃(PyTrz)₈(H₂O)₄](NO₃)₆ (M = Co, Ni), were synthesized and studied by X-ray diffraction, magnetochemical method, and electronic and IR spectroscopy. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆) was also studied by adiabatic calorimetry. The Fe(II), Co(II), and Ni(II) nitrate complexes were shown to be isostructural to the previously synthesized linear trinuclear [Cu₃(PyTrz)₈H₂O)₄](NO₃)₆ complex. In all compounds, antiferromagnetic exchange interactions between M²⁺ ions were detected. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆ undergoes the ¹ A ₁ ⁵ T ₂ spin transition.     

Synthesis,electrochemical and e.p.r. spectral studies of binuclear copper(II) complexes with new pentadentate L-proline-based binucleating ligands

The synthesis, reduction, optical and e.p.r. spectral properties of a series of new binuclear copper(II) complexes, containing bridging moieties (OH^–, MeCO₂ ^–, NO₂ ^–, and N₃ ^–), with new proline-based binuclear pentadentate Mannich base ligands is described. The ligands are: 2,6-bis[(prolin-1-yl)methyl]4-bromophenol [H₃L¹], 2,6-bis[(prolin-1-yl)methyl]4-t-butylphenol [H₃L²] and 2,6-bis[(prolin-1-yl)methyl]4-methoxyphenol [H₃L³]. The exogenous bridging complexes thus prepared were hydroxo: [Cu₂L¹(OH)(H₂O)₂] · H₂O (1a), [Cu₂L²(OH)(H₂O)₂] · H₂O (1b), [Cu₂L³(OH)(H₂O)₂] · H₂O (1c), acetato [Cu₂L¹(OAc)] · H₂O (2a), [Cu₂L²(OAc)] · H₂O (2b), [Cu₂L³(OAc)] · H₂O (2c), nitrito [Cu₂L¹(NO₂)(H₂O)₂] · H₂O (3a), [Cu₂L²(NO₂)(H₂O)₂] · H₂O (3b), [Cu₂L³(NO₂)(H₂O)₂] · H₂O (3c) and azido [Cu₂L¹(N₃)(H₂O)₂] · H₂O (4a), [Cu₂L²(N₃)(H₂O)₂] · H₂O (4b) and [Cu₂L³(N₃)(H₂O)₂] · H₂O (4c). The complexes were characterized by elemental analysis and by spectroscopy. They exhibit resolved copper hyperfine e.p.r. spectra at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. The strength of the antiferromagnetic coupling lies in the order: NO₂ N₃ OH OAc. Cyclic voltammetry revealed the presence of two redox couples Cu^IICu^II Cu^IICu^I Cu^ICu^I. The conproportionality constant K _con for the mixed valent Cu^IICu^I species for all the complexes have been determined electrochemically.     

Cyanide-bridged [Fe8M6] clusters displaying single-molecule magnetism (M=Ni) and electron-transfer-coupled spin transitions (M=Co)

Cyanide‐bridged metal complexes of [Fe₈M₆(μ‐CN)₁₄(CN)₁₀ (tp)₈(HL)₁₀(CH₃CN)₂][PF₆]₄?n CH₃CN?m H₂O (HL=3‐(2‐pyridyl)‐5‐[4‐(diphenylamino)phenyl]‐1H‐pyrazole), tp^?=hydrotris(pyrazolylborate), 1 : M=Ni with n=11 and m=7, and 2 : M=Co with n=14 and m=5) were prepared. Complexes 1 and 2 are isomorphous, and crystallized in the monoclinic space group P2₁/n. They have tetradecanuclear cores composed of eight low‐spin (LS) Fe^III and six high‐spin (HS) M^II ions (M=Ni and Co), all of which are bridged by cyanide ions, to form a crown‐like core structure. Magnetic susceptibility measurements revealed that intramolecular ferro‐ and antiferromagnetic interactions are operative in 1 and in a fresh sample of 2 , respectively. Ac magnetic susceptibility measurements of 1 showed frequency‐dependent in‐ and out‐of‐phase signals, characteristic of single‐molecule magnetism (SMM), while desolvated samples of 2 showed thermal‐ and photoinduced intramolecular electron‐transfer‐coupled spin transition (ETCST) between the [(LS‐Fe^II)₃(LS‐Fe^III)₅(HS‐Co^II)₃(LS‐Co^III)₃] and the [(LS‐Fe^III)₈(HS‐Co^II)₆] states.     

Isostructural triazenido complexes of first row transition metals. Part 3. Low spin cyclopentadienyl complexes of cobalt(II) (η5-C5H5)(PPh3)(RN3R)Co

Summary Reaction of (PPh₃)₂Cl₂Co^II with TlC₅H₅ gave the new ( ⁵-C₅H₅)(PPh₃)ClCo^II complex. This complex reacted with Ag(RN₃R) or Cu(RN₃R) (R=p-MeC₆H₄,p-ClC₆H₄ or 3,5-Cl₂C₆H₃) to give the novel compounds ( ⁵-C₅H₅)(PPh₃)(RN₃R)Co^II, with a spin state of one half, which are representatives of the very small class of paramagnetic monocyclopentadienyl transition metal complexes. The structural conclusions are based on comparison with the isostructural [ ⁵-C₅H₅)(PPh₃)(RN₃R)Co^III]PF₆ complex, on the i.r. spectra and on the observed redox behaviour. The e.p.r. spectra are reported, but are not well enough resolved for the determination of the hyperfine interactions. The orbital scheme of the new complex is discussed in terms of a distorted octahedral crystal field in relation to the series of isostructural ( ⁵-C₅H₅)(PPh₃)(RN₃R)M^II (M = Fe, Co or Ni) complexes.     

Synthesis and spectral characterization of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,4- bis (2-carboxyaldehydephenoxy)butane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:15,16-tribenzo-9,15-dioxacycloheptadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine with 1,4-bis(2-carboxyaldehydephenoxy)butane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,4-bis (2-carboxyaldehydephenoxy)butane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La (NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes were characterized by elemental analysis, IR, ¹H- and ¹³C-n.m.r., UV-vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements and mass spectra. All complexes are diamagnetic and the Cu^II complex is binuclear. The Co^II complex was oxidised to Co^III.     

The2 E↔4 A 2 transition in tetragonal Cr3+ complexes

The² E⁴ A ₂ absorption and emission spectra of [Cr(NH₃)₅(NO₃)](NO₃)₂, [Cr(NH₃)₅(NO₂)] ·(NO₃)₂, and [Cr(NH₃)₅(H₂O)](NO₃)₃ microcrystals have been recorded at 77°K. Tetragonal²E splittings are 209, 188 and 87 cm^–1, respectively. An analysis of the limited vibronic structure has been made and compared to the results for the parent octahedral complex, [Cr(NH₃)₆](NO₃)₃. Vibrations of approximately 270 and 700 cm^–1 are prominent.

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Zusammenfassung Die² E⁴ A ₂ Absorptions- und Emissionsspektren von [Cr(NH₃)₅(NO₃)](NO₃)₂-, [Cr(NH₃)₅ (NO₂)](NO₃)₂- und [Cr(NH₃)₅(H₂O)](NO₃)₃-Mikrokristallen werden für 77° angegeben. Die tetragonalen² E Aufspaltungen sind209, 188 bzw. 87 cm^–1. Eine Analyse der begrenzten vibronischen Struktur wurde vorgenommen und mit den Resultaten für den oktaedrischen Stammkomplex, [Cr(NH₃)₆](NO₃)₃ verglichen. Schwingungen von etwa 270 und 700 cm^–1 treten besonders hervor.

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Résumé Les spectres d'émission et d'absorption² E⁴ A ₂ de microcristaux de [Cr(NH₃)₅(NO₃)](NO₃)₂, [Cr(NH₃)₅(NO₂)](NO₃)₂ et [Cr(NH₃)₅(H₂O)](NO₃)₃ ont été enregistrés à 77° K. Les écartements tétragonaux² E sont respectivement 209, 188 et 87 cm^–1. Une analyse de la structure vibronique limitée a été effectuée et comparée aux résultats pour le complexe octaédral parent [Cr(NH₃)₆](NO₃)₃. Les vibrations au voisinage de 270 et 700 cm^–1 émergent.

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This contribution is dedicated to the memory of Prof. Hans-Ludwig Schläfer, a stimulating colleague and valued friend.     

Koordinationsverbindungen des zweiwertigen Nickels und dreiwertigen Kobalts mit Äthylendiimino-bis-acetylaceton

The preparation of compounds with formula Ni(enac ₂) and [Co(enac ₂)L ₂]X is reported [H₂(enac ₂)=ethylenediimino-bis-acetylacetone, C₁₂H₂₀N₂O₂,L=NH₃,py, -pic, diethylamine;X=Cl^–, ClO _– ⁴ , B(C₆H₅) _– ³ ]. The complexes have been studied by means of magnetic susceptibility measurements, infrared, electronic and NMR spectra and conductivity measurements.     

Oligonuclear 3d–4f Complexes as Tectons in Designing Supramolecular Solid‐State Architectures: Impact of the Nature of Linkers on the Structural Diversity

Heteronuclear cationic complexes, [LCuLn]³⁺ and [(LCu)₂Ln]³⁺, were employed as nodes in designing high‐nuclearity complexes and coordination polymers with a rich variety of network topologies (L is the dianion of the Schiff base resulting from the 2:1 condensation of 3‐methoxysalycilaldehyde with 1,3‐propanediamine). Two families of linkers have been chosen: the first consists of exo‐dentate ligands bearing nitrogen‐donor atoms (bipyridine (bipy), dicyanamido (dca)), whereas the second consists of exo‐dentate ligands with oxygen‐donor atoms (anions derived from the acetylenedicarboxylic (H₂acdca), fumaric (H₂fum), trimesic (H₃trim), and oxalic (H₂ox) acids). The ligands belonging to the first family prefer copper(II ) ions, whereas the ligands from the second family interact preferentially with oxophilic rare‐earth cations. The following complexes have been obtained and crystallographically characterized: [LCu^II(OH₂)Gd^III(NO₃)₃] ( 1 ), [{LCu^IIGd^III(NO₃)₃}₂(μ‐4,4′‐bipy)] ( 2 ), [LCu^IIGd^III(acdca)_1.5(H₂O)₂] ? 13 H₂O ( 3 ), [LCu^IIGd^III(fum)_1.5(H₂O)₂] ? 4 H₂O ? C₂H₅OH ( 4 ), [LCu^IISm^III(H₂O)(Hfum)(fum)] ( 5 ), [LCu^IIEr^III(H₂O)₂(fum)]NO₃ ? 3 H₂O ( 6 ), [LCu^IISm^III(fum)_1.5(H₂O)₂] ? 4 H₂O ? C₂H₅OH ( 7 ), [{(LCu^II)₂Sm^III}₂fum₂](OH)₂ ( 8 ), [LCu^IIGd^III(trim)(H₂O)₂] ? H₂O ( 9 ), [{(LCu^II)₂Pr^III}(C₂O₄)_0.5(dca)]dca ? 2 H₂O ( 10 ), [LCu^IIGd^III(ox)(H₂O)₃][Cr^III(2,2′‐bipy)(ox)₂] ? 9 H₂O ( 11 ), and [LCuGd(H₂O)₄{Cr(CN)₆}] ? 3 H₂O ( 12 ). Compound 1 is representative of the whole family of binuclear Cu^II–Ln^III complexes which have been used as precursors in constructing heteropolymetallic complexes. The rich variety of the resulting structures is due to several factors: 1) the nature of the donor atoms of the linkers, 2) the preference of the copper(II ) ion for nitrogen atoms, 3) the oxophilicity of the lanthanides, 4) the degree of deprotonation of the polycarboxylic acids, 5) the various connectivity modes exhibited by the carboxylato groups, and 6) the stoichiometry of the final products, that is, the Cu^II/Ln^III/linker molar ratio. A unique cluster formed by 24 water molecules was found in crystal 11 . In compounds 2 , 3 , 4 , 9 , and 11 the Cu^II–Gd^III exchange interaction was found to be ferromagnetic, with J values in the range of 3.53–8.96 cm^?1. Compound 12 represents a new example of a polynuclear complex containing three different paramagnetic ions. The intranode Cu^II–Gd^III ferromagnetic interaction is overwhelmed by the antiferromagnetic interactions occurring between the cyanobridged Gd^III and Cr^III ions.     

“From Heteronuclear Complex to Composite Oxide” Approach in the Synthesis of Nanosized Ferrites MIIFeIII 2O4 (M = Mn,Co, Ni) with Spinel Structure and Their Catalytic Properties

A study was carried out on the preparation of ferrites M^IIFe₂O₄ (M^II = Mn, Co, Ni) by the thermal decomposition of the corresponding ₃-oxoacetates [Fe₂M^IIO(CH₃COO)₆(H₂O)₃]·2H₂O. Nanocrystallites of M^IIFe₂O₄ were formed under mild conditions at 300-400 °C in this reaction. An increase in the temperature leads to an increase in particle size. Nickel ferrite showed high catalytic activity in the reduction of nitrogen oxides (NO _x ) by hydrocarbons.