Thermal properties of solid nickel(II) coordination compounds

The paper deals with the chemical and physical factors influencing the thermal octahedral square planar changes of nickel(II) complexes in the solid phase. The relationship between these transformations and the tetragonal distortion of the octahedral ligand field is discussed. Depending on the coordination of the ligands, these transformations can be divided into two groups: octahedral monomer square planar monomer, and octahedral polymer square planar monomer changes. Attention is directed only to octahedral and square planat Ni(II) complexes (square planar complexes with chromophores [NiN₄], [NiN₂O₂] and [NiO₄]), which can be isolated in the solid state before and after heating. The possibility of such a configurational change seems to be dependent upon the thermal stabilities of the initial and final complexes, the electronic and steric properties of the ligands, the complexing ability of the central atom, and particularly the equatorial-axial interactions of the ligands via the central atom.

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Zusammenfassung Vorliegende Arbeit befasst sich mit den chemischen und physikalischen Faktoren, die den thermischen Übergang oktaedrisch-rechteckig planar der Festkörperphase von Nickel(II) komplexen beeinflussen. Es werden die Beziehungen zwischen dieser Transformation und der tetragonalen Verzerrung oktaedrischer Ligandenfelder besprochen. Entsprechend der Koordinierung der Liganden können diese Transformationen in zwei Gruppen eingeteilt werden: monomer oktaedrisch-monomer rechteckig planar sowie polymer oktaedrisch-monomer rechteckig planare. Hier werden nur solche oktaedrische und rechteckig planare Ni(II)komplexe (rechteckig planare Komplexe mit (NiN₄)-, (NiN₂O₂)- und (NiO₄)-Chromophoren) betrachtet, die sowohl vor als auch nach dem Erhitzen in fester Form isoliert werden können. Die Möglichkeit solcher Konfigurationsübergange scheint von der thermischen Stabilität der Ausgangs- und Produktekomplexe, von elektronischen und sterischen Eigenschaften der Liganden, von der Komplexbildungsstärke des Zentralatomes und hauptsächlich von den äquatorial-axialen Wechselwirkungen der Liganden gegenüber dem Zentralatom abzuhängen.

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, . . , : . - ( [NiN₄], [NiN₂O₂] [NiO₂]), . , , , , , — .

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Part A: J. Thermal Anal., 16 (1979) 213.     

Thermal properties of solid nickel(II) coordination compounds

The paper deals with the chemical and physical factors influencing the stoichiometry of thermal decomposition of solid coordination compounds. Nickel(II) coordination compounds were used as examples: the problem of the relationship between the structure of the initial compound (and of its intermediates) and the stoichiometry of thermal decomposition is discussed; experimental conditions are shown to affect this decomposition, and the conceptions of the apparent and real stoichiometries of thermal decomposition are discussed. The results obtained may have a more general meaning.

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Zusammenfassung Der Beitrag befa\t sich mit den chemischen und physikalischen Faktoren, welche die Stöchiometrie der thermischen Zersetzung fester Koordinationsverbindungen beeinflussen. Koordinationsverbindungen von Nickel(II) wurden als Beispiel eingesetzt; das Problem des Zusammenhanges zwischen Struktur der Ausgangsverbindung (und seiner IntermediÄrprodukte) und der Stöchiometrie der thermischen Zersetzung wird erörtert; die die Zersetzung beeinflussenden Versuchsbedingungen werden gezeigt und das Konzept der sogenannten scheinbaren und tatsÄchlichen Stöchiometrie der thermischen Zersetzung wird beschrieben. Die erhaltenen Ergebnisse dürften von allgemeinerer Bedeutung sein.

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Résumé L'article considère les facteurs chimiques et physiques qui influencent la stchiométrie des réactions de décomposition thermique des composés de coordination solides. Les composés de coordination du nickel(II) ont été choisis pour illustrer le problème des relations entre la structure du composé initial (et de ses intermédiaires) et la stchiométrie de la réaction de décomposition thermique. On montre que les conditions expérimentales influencent la décomposition et on discute le principe des réactions stchiométriques de décomposition thermique dites «apparentes» et «réelles». Les résultats obtenus sont probablement de portée plus générale.

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, . $ (II) $ ( ) $ . , $ , $ . .

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Reported at the 7th Seminar on Modern Methods in Inorganic Chemistry. Harmonia-Bratislava, 1977.     

Spin-crossover in coordination compounds of iron(II) with tris(pyrazol-1-yl)methane and cluster anions

Synthesis procedures for new coordination compounds of iron(II) with tris(pyrazol-1-yl)methane (HC(pz)₃), containing cluster anions in the outer sphere, of the composition [Fe{HC(pz)₃}₂][Mo₆Cl₁₄]?2H₂O (I), [Fe{HC(pz)₃}₂][Mo₆Br₁₄]?H₂O (II), and [Fe{HC(pz)₃}₂]₂[Re₆S₈(CN)₆]?2H₂O (III) are developed. The compounds are studied by static magnetic susceptibility, electronic, IR, and Mössbauer spectroscopic methods. The magnetochemical study shows that in the polycrystalline phases of all compounds the spincrossover ¹ А ₁ ? ⁵ Т ₂ is observed which is accompanied by thermochromism.     

Mass-spectrometric investigation of the coordination compounds of oxovanadium(IV), cobalt(II), nickel(II), copper(II), and zinc(II) with ligands based ON S-substituted isothiosemicarbazides,salicyaldehyde, and 3-formylacetylacetone

A general scheme is proposed for the electron impact fragmentation of the coordination compounds of VO(II), Co(II), Ni(II), Cu(II) and Zn(II) with tetradentate chelating ligands based on S-substituted isothiosemicarbazides, salicylaldehyde, and 3-formylacetylacetone and also the corresponding free ligands. It was established that one of the main factors which determine the direction and degree of fragmentation of the complexes is the ability of the central metal atom to change its oxidation state. It was found that complex formation with the free ligands and exchange of the metal in the metal complexes take place as side processes on the walls of the ionization chamber of the mass spectrometer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2248–2256, October, 1989.The authors are grateful to M. M. Timoshenko and Yu. V. Chizhov for assistance afforded during the recording of the photoelectron spectra.     

Cobalt(II), nickel(II) and zinc(II) coordination compounds derived from aromatic amines

The structural and spectroscopic characterization of coordination compounds of four aromatic amines derived from benzimidazole, 2-aminobenzimidazole (L1), 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2), 2-(2-aminophenyl)-1H-benzimidazole (L3) and 6,6-dimethyl-5H-benzimidazolyl[1,2-c]quinazoline (L4) are reported. Cobalt(II) [Co(L1)₂(CH₃COO)₂] (1) and nickel(II) [Ni(L1)₂(CH₃COO)₂] (2) acetate coordination compounds of L1 are discussed. The synthesis and the X-ray crystal structure of the new 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2) is informed, together with its cobalt(II) [Co(L2)₂Cl₂] (3), [Co(L2)₂Br₂] (4) and zinc(II) [Co(L2)₂Cl₂] (5), [Zn(L2)₂Br₂] (6) coordination compounds. In these compounds the imidazolic nitrogen is coordinated to the metal center, while the ArNH₂ and the S-methylcarbodithioate groups do not participate as coordination sites. A co-crystal of L1 and L2 is analyzed. Structural analyses of the coordination compounds of L3 showed that this ligand behaves as a bidentate ligand through the aniline and the imidazole groups forming six membered rings in the cobalt(II) [Co(L3)Cl₂] (7) and zinc(II) [Zn(L3)Cl₂] (8) compounds, as well as the nickel(II) nitrate [Ni(L3)₂(H₂O)₂](NO₃)₂ (9). The quinazoline L4 was produced by insertion of one acetone molecule and water elimination in L3, its X-ray crystal diffraction analysis, as well as that of its zinc(II) coordination compound [Zn(L4)₂Cl₂] (10), are discussed.     

Different-ligand coordination compounds of nickel(II) with 1,3-dicarboxypropane-1-iminodiacetic acid and dicarboxylic acids in aqueous solutions

The equilibria in the ternary systems containing a nickel(II) salt and 1,3-dicarboxypropane-1-iminodiacetic acid and dicarboxylic acids (oxalic, malonic and succinic) were studied by spectrophotometry with supporting perchlorate (NaClO₄) for I = 0.1 at T = 20 ± 2°C. The stoichiometry and pH regions of existence of different-ligand complexes were determined; the stability constants of these complexes were calculated. The accumulation fractions of the complexes as functions of acidity were found. The experimental data were treated with mathematical models that estimate the possibility of existence of a broad range of complex species in solution and distinguish those of them that are sufficient to reproduce the observed picture.     

Copper(II) coordination compounds with ferulic acid

The first two molecular structures of the ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid, C₁₀H₁₀O₄) coordination compounds are presented, namely, [Cu₂(C₁₀H₉O₄)₄(CH₃CN)₂] 1 and [Cu₂(C₁₀H₉O₄)₄(C₆H₆N₂O)₂]·4CH₃CN (C₆H₆N₂O = nicotinamide) 2. Both compounds were synthesised from the starting mixture of Cu₂O and CuCl upon copper oxidation in the acetonitrile solution. The single-crystal X-ray diffraction analysis of 1 and 2 reveals the binuclear structure of the ‘paddle–wheel’ type for both complexes. 1 and 2 are unstable outside mother liquid due to loosely bound acetonitrile molecules. The final products of decomposition are [Cu₂(C₁₀H₉O₄)₄] 1a and [Cu₂(C₁₀H₉O₄)₄(C₆H₆N₂O)₂] 2a, which were characterized by several physico-chemical methods. The triplet X-band EPR spectra of 1a and 2a, showing signals B_Z1  15 mT, B₂  460 mT and B_Z2  580 mT, are in agreement with the expected data for the binuclear tetracarboxylate units, found in the structures of the parent complexes 1 and 2. Together with the room temperature magnetic susceptibility data, μ_eff/B.M. 1.40 (1a), 1.48 (2a), the EPR spectra analysis confirm the antiferromagnetic interaction in 1a and 2a. This is suggesting preservation and stability of the paddle–wheel structures in 1a and 2a.     

Novel coordination compounds of nickel(II) and copper(II) with N,Nprime-diphenylthiooxamide; formation of complexed metalhexacyanoferrate(II) gelatin-immobilized matrix systems

A novel route to complexes of NiII and CuII with N,Nprime-diphenylthiooxamide, namely complexing in a NiII or CuII hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the N,Nprime-diphenylthiooxamide, has been studied. Under these specific conditions, in the NiII system, four different coordination compounds are formed, three of which are insoluble in H2O; in the CuII system, only one insoluble complex is formed. When complexation is carried out in solution or the solid phase, formation of only one complex is observed in each of systems studied. This revised version was published online in June 2006 with corrections to the Cover Date.     

Polymeric coordination compounds of nickel(II), cobalt(II), and zinc(II) with oxalate ions as symmetric tetradentate bridging ligands

Summary Coordination compounds having the general formula ML₂Ox are described, with Ox = oxalato dianion; M = Ni, Co and Zn; 1 = water and imidazoles. The compounds are characterised by chemical analyses, i.r., far-i.r., Raman, ligand field and e.s.r. spectra. Magnetic susceptibility measurements at low temperatures indicate a polymeric structure of ant i-ferromagnetically coupled M²⁺ ions.All physical measurements agree with a polymeric structure built up by oxalate ions as tetradentate bridging ligands forming one-dimensional linear chains. Flach metal ion is coordinated by four oxalate oxygens and two donor atoms (N or O) in distorted octahedron. For M = Ni, the magnetic susceptibility measurements can be best described with the Heisenberg model including a zero-field splitting; for M = Co, the Ising model gives the best results. The exchange coupling constants, IJ1, vary from 9-13 cm^–1.     

Nickel(II) and cobalt(II) coordination compounds of dichloroguanidinopyrimidines

Summary New coordination compounds of Ni^II and Co^II with dichloropyrimidinoguanidine (L) have been obtained and characterized by physico-chemical and spectroscopic methods. The complexes have the general formulae: [ML₃](ClO₄)₂, [ML₂(SO₄)], [ML₂(NCS)₂], (M = Ni or Co), [NiL₂(ClO₄)₂] and [CoL₂](ClO₄)₂. The ligands are bonded to the metal ion via one nitrogen atom from the pyrimidine heterocyclic ring and one from the guanidine group.     

Isomerism of copper(II) coordination compounds with hydroxamic acids

The structure of Cu^II complexes with hydroxamic acids Cu[R¹N(O)−(O)CR²]₂, where R¹=Ph, R²=Me; R¹=Me, R²=Ph, was studied by ESR spectroscopy. In toluene solutions and low-temperature glasses, the complexes exist as two forms, which were identified ascis-andtrans-isomers. The proportions of the isomers were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 726–729, April, 1999.     

Synthesis of copper(II) coordination compounds with benzoxazine derivatives

Copper(II) complexes with 1,2-dihydro-4H-3,1-benzoxazine (HL) derivatives, CuLOH, were prepared by anodic electrosynthesis. The use of an amalgamated copper anode resulted in an increase in the electrosynthesis rate. It follows from the IR spectra of the products that the benzoxazine ring in the ligand molecule is opened upon complexation, while a six-membered chelate ring involving the oxygen atom of the deprotonated phenol group and the imine nitrogen atom is formed.     

New coordination compounds of palladium(II) with iminodiacetic acid

Summary Iminodiacetic acid (IDA) forms 1:1 or 1:2 complexes with Pdll at room temperature and pH 6.0. The solid compounds have been characterized by elemental analysis, titrimetry, magnetic measurements, i.r. spectroscopy and thermal studies. The far i.r. spectra show peaks that can be assigned to Pd-Cl, Pd-N and Pd-O vibrations. On the basis of these studies tentative structures for the isolated substances are proposed.     

From novel complexing conditions to novel coordination compounds of nickel(II) with dithiooxamide and its bulky analogues

Summary Novel complexing processes in the Ni^II-dithiooxamide, Ni^II-N,N-diphenyldithiooxamide and Ni^II-quinoxaline-2,3-dithiol systems, which have not been used in coordination chemistry before, namely complexing in a nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the corresponding ligand, have been studied. Under these specific conditions, in the Ni^II-dithiooxamide system, five different coordination compounds are formed, four of which are insoluble in H₂O. In the Ni^II-quinoxaline-2,3-dithiol system, three different complexes formed (each of them insoluble in H₂O) and, in the Ni^II-diphenyldithiooxamide system, only one insoluble complex is formed. Whereas, complexing in solution or the solid phase, formation of only one complex is observed in each of systems cited     

Versatility of copper(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine mediated by temperature,solvents and anions choice

Tuning reaction temperatures as well as the variation in starting copper salts and solvents led to the formation of a new series of Cu(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine (dpp): a mononuclear [Cu(acac)(dpp)(NO₃)] (1) complex, two dinuclear [Cu₂(acac)₂(dpp)(NO₃)(H₂O)]NO₃ (2) and [Cu₂(Hdpp)₂(ox)(Cl)₂(H₂O)₂]Cl₂·6(H₂O) (4) complexes, and four coordination polymers {[Cu₄(dpp)₂(ox)(Cl)₆]}_n (3), {[Cu₄(dpp)₂(ox)(NO₃)₆(H₂O)₂]∙1.2(H₂O)}_n (5), {[Cu(dpp)(NO₃)](NO₃)·(H₂O)}_n (6) and {[Cu(dpp)(SO₄)(H₂O)₂]}_n (7), where acac⁻ = acetylacetonate, ox²⁻ = oxalate. Remarkably, the treatment of Cu(II) chloride dihydrate with dpp in methanol solution led to an unusual in situ condensation of dpp with acac⁻ to produce [Cu₂(acdpp)₂(Cl)₄]·2(MeOH) (8). The structure of 1 consists of neutral, mononuclear [Cu(acac)(dpp)(NO₃)] units with acac⁻ and dpp acting as bidentate ligands. In 2, the dpp ligand coordinates in a bis-chelating mode to two Cu(II) ions and bridges them into a dimeric entity, whereas an oxalate linker joins [Cu(Hdpp)(Cl)₂(H₂O)]⁺ units into a dimer in 4. Compounds 3, 5, 6 and 7 are 1D chain coordination polymers, which incorporate two symmetry independent metal centers and different bridging ligands: Hdpp⁺ as a protonated cationic or dpp as a neutral chelating ligand and oxalate, Cl⁻ anions or sulfate di-anions as bridging ligands. Magnetic studies were performed on samples 1 and 2, and the analysis reveals a very weak magnetic exchange coupling mediated via the dpp ligand.     

Mass spectrometric study of isomeric coordination compounds of nickel(II) with octaazamacrocyclic ligands based on SR-isothiocarbohydrazide and unsymmetrical α-dicarbonyl compounds

A study has been made of isomeric complexes of nickel(II) with octaazamacrocyclic ligands based on SR-isothiocarbohydrazide and unsymmetrical -dicarbonyl compounds, and also their deuterio analogs. It has been found that the mass spectra of such compounds become more characteristic with increasing energy of the ionizing electrons. Overall paths of fragmentation have been proposed, as well as a scheme for interconversion of structural isomers due to delocalization and migration of the metal-ligand bond in the gas phase under electron impact. Feasibility has been demonstrated for identification of isomers of the basis of the character of fragmentation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 3, pp. 311–316, May–June, 1989.     

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)     

On the structure of copper(II) coordination compounds with L-histidine

Quantum chemical calculations are performed for the spatial and electron structure of complex compounds of L-histidine and its ionized forms with copper(II) for a variety of compositions within the density functional theory (DFT) using the B3LYP functional and 6-311G(d) basis. The solvent (water) is considered within the PCM approximation. EPR spectroscopy is used to study the equilibrium in the copper(II)–L-histidine system in an aqueous solution at рН 2–11. A comparison between the theoretical calculations and the EPR spectra suggests the following geometry for the coordination environment of the copper(II) ion in the complex compounds: CuHLL–square-planar coordination; CuL₂, CuHLL′, and CuLL′–distorted square pyramid; and CuL₂′–octahedral environment.