Thermal analysis of complexes of cadmium chloride picoline

The thermal decomposition of the, and- picoline complexes of cadmium were studied by means of TG-DTG-DTA. In connection with the preparation of the complex compounds, it was established that the ligand number was influenced by the reaction medium. The thermal decomposition took place stepwise, and intermediates were formed which could be isolated with a derivatograph by the freezing-in method. The structures and properties of these previously unknown compounds were investigated by far-IR spectroscopy and X-ray powder diffraction.

---

Zusammenfassung Der thermische Zersetzungsprozess der Komplexverbindungen von Cadmiumchlorid mit-, - oder-Picolin wurde durch simultane TG-DTG-DTA im Derivatograph untersucht. Die Ligandenzahl der Komplexverbindungen wird durch das Reaktionsmedium bei der Präparation beeinflusst. Die thermische Zersetzung erfolgt stufenweise, Zwischenprodukte konnten mittels Derivatograph durch die Einfriermethode isoliert werden. Struktur und Eigenschaften dieser bisher unbekannten Verbindungen wurden durch Fern-IR-Spektroskopie und Röntgenpulverbeugung untersucht.

---

- -, -. , . , « ». .

     

Complexes of mixed silicon halides with 4‐picoline

The reaction products of an addition reaction of five different silicon tetrahalides with the aromatic nitro­gen base 4‐methyl­pyridine are presented. The following five structures are isomorphous: (I) tetra­chloro­bis(4‐methyl­pyridine)­silicon, C₁₂H₁₄­Cl₄­N₂Si, (II) bromo­tri­chloro­bis(4‐methyl­pyridine)­silicon, C₁₂H₁₄­Br­Cl₃N₂Si, (III) di­bromo­di­chloro­bis(4‐methyl­pyridine)­silicon, C₁₂H₁₄­Br₂­Cl₂N₂Si, (IV) tri­bromo­chloro­bis(4‐methyl­pyridine)­silicon, C₁₂H₁₄Br₃­Cl­N₂Si, and (V) tetra­bromo­bis(4‐methyl­pyridine)­silicon, C₁₂H₁₄Br₄N₂Si. The mol­ecules of (I) and (V), with D_2h symmetry, have crystallographic C_2h symmetry, while the molecules of (II), (III) and (IV) have a lower molecular symmetry, but as a result of the disorder of the halogen ligands, they appear to be of the same crystallographic symmetry. The environment around the Si atom can be described as a slightly distorted octahedron with the methyl­pyridine ligands occupying axial positions and the four halogen ligands in the equatorial plane. In spite of the different substitution pattern of the silicon centre, there are only insignificant differences between these five structures.     

A differential scanning calorimetry study of picoline complexes of cadmium chloride

The decomposition of picoline complexes of cadmium chloride has been studied using differential scanning calorimetry. The 2:1 complexes with 3-picoline and 4-picoline decompose in three steps corresponding to the loss of one, one-third, and two-thirds of a molecule of ligand, respectively, in these steps. Sample size apparently controls the mode of decomposition of the 1:1 complex with 2-picoline. In some cases, two-thirds of a molecule of ligands is lost and in other cases one-third is lost first. Thermal parameters have been determined for the various decomposition reactions.     

Gossypol clathrates: Structure and thermal behavior of gossypol solvates with two picoline isomers

Gossypol forms stable solvates with 4- and 2-picolines at room temperature. The solvates are investigated by single crystal X-ray diffraction and thermal analysis. Solvate crystals of gossypol with 4-picoline (1) have the 1:3 composition (gossypol:4-picoline) and crystallize in the P2₁/c space group. This substance is isostructural to a trisolvate of gossypol with pyridine. Solvate crystals of gossypol with 2-picoline (2) have the 1:4 composition (gossypol:2-picoline) and crystallize in the P-1 space group. The unit cell parameters for the investigated structures are as follows: 1 monoclinic crystals, C₃₀H₃₀O₈·3C₆H₇N, a = 10.7530(1) ?, b = 20.7834(3) ?, c = 19.1166(2) ?, β = 95.537(1)°, V = 4252.32(9) ?³, M = 797.92, Z = 4, d _x = 1.246 g/cm³, and R = 0.0489 for 4102 reflections; 2 triclinic crystals, C₃₀H₃₀O₈·4C₆H₇N, a = 11.467(1) ? b = 14.962(2) ?, c = 15.570(3) ?, α = 75.62(1)°, β = 69.83(1)°, γ = 79.58(1)°, V = 2414.6(7) ?³, M = 891.04, Z = 2, d _x = 1.226 g/cm³, and R = 0.0528 for 3779 reflections. The results of the single crystal XRD and thermal analysis confirm that gossypol with 4-picoline forms a trisolvat, and a tetrasolvate with 2-picoline. The transition from 4-picoline to 2-picoline proves to change the type of the host-guest association from one-dimensional to zero-dimensional, i.e., to lead to a new crystal structure. Desolvation of compound 2 begins at a lower temperature than that for compound 1, which is explained by their different crystal structures. Keywords: gossypol, 4-picoline, 2-picoline, clathrate formation, crystal structure.     

Synthesis, structural, thermal and optical studies of 1-ethyl-2,6-dimethyl-4-hydroxy pyridinium halides

1-Ethyl-2,6-dimethyl-4-hydroxy pyridinium chloride dihydrate and bromide dihydrate salts have been synthesized and their single crystals were grown by the slow evaporation of aqueous solution at 30 degrees C. The grown crystals were characterized by elemental analysis, FT-NMR and FT-IR techniques to confirm the formation of the expected compound. Optical transmittance window in aqueous solution was found to be 275-1100 nm by UV-vis-NIR technique. Thermogravimetric and differential thermal analyses reveal thermal stability and the presence of two water molecules in the crystal lattices. The crystal structure of chloride salt was also determined by X-ray diffraction method.     

Synthetic and structural chemistry of amidinate-substituted boron halides

The following new amidinate-substituted boron halides are reported: [PhC{N(SiMe(3))}(2)]BCl(2)(6), [MeC{NCy}(2)]BCl(2)(10), [Mes*C{NCy}(2)]BCl(2)(11), [MeC{N(i)Pr}(2)]BCl(2)(12), and [FcC{NCy}(2)]BBr(2)(13). Compound 6 was prepared via the trimethylsilyl chloride elimination reaction of BCl(3) with N,N,N'-tris(trimethylsilyl)benzamidine, and compounds 10-12 were prepared by salt metathesis between the lithium amidinates [RC(NR')(2)]Li and BX(3). Compound 13 was prepared via the insertion of 1,3-dicyclohexylcarbodiimide into the B-C bond of ferrocenyldibromoborane FcBBr(2). The molecular structures of 6, 10, 11, 13 and the known compound [PhC{N(SiMe(3))}(2)]BBr(2)(1) were established by single-crystal X-ray diffraction.     

Some unexpected reactions of perfluoroalkynylmagnesium halides

R_FCCMgX reacts with Ac₂O to give not only MeC(O)CCR_F but also MeC(O)CXC(R_F)C(O)Me, and with CF₃COOPr it gives CF₃C(O)CHC(OPr)R_F not CF₃C(O)CCR_F; R_FCCMgBr reacts with Cl₂ to give R_FCCBr rather than R_FCCCl, while with Br₂ R_FCCMgI similarly gives R_FCCI rather than R_FCCBr.     

Exafs structural parameters for some titanium halides

α-TiCl₃ and TiCl₂ were subject to an X-ray absorption spectroscopic study at the K threshold of titanium. Data analysis was performed by Fourier methods and curve fitting techniques. Using the theoretical phases and coordination numbers Ti-Cl distances of 2.46(1) and 2.42(1) Å are derived for α-TiCl₃ and TiCl₂, respectively, as compared to the crystallographic values of 2.46(1) and 2.50(?) Å. The observed discrepancy in case of TiCl₂ is discussed. The EXAFS results are confirmed by Rabe's evaluation procedure for the absorber-backscatterer interatomic distance (R, Å) as a function of the photoelectron wave vector k (Å^?1).     

Stereochemistry and structural phase transition of Cu(II) complexes containing orthophosphate ions and pyridine/picoline

Copper complexes of the type Cu(L)₄(H₂PO₄)₂ designated as complex (I), and Cu(L)₄ HPO₄ designated as complex (II), (whereL = pyridine (py) or λ-picoline (pic)) have been synthesised, characterised by chemical analyses, IR, and electronic and magnetic susceptibility data. From ESR studies it is concluded that complexes (I) have elongatedtrans octahedral stereochemistry. The temperature dependence of the ESR spectrum of Cu(py)₄(H₂PO₄)₂ suggests a fluxional behaviour in the immediate coordination of Cu(II), whereas very little variation of the ESR spectrum of the Cu(pic)₄(H₂PO₄)₂ complex indicates that the stereochemistry of this complex is essentially static in nature. The differential scanning calorimetric studies in the case of Cu(py)₄(H₂PO₄)₂ complex have given clear evidence for the occurrence of a structural phase transition at 147 K. The absence of any abrupt changes in the ESR spectrum at that temperature excludes the possibility of any changes in the immediate environment of Cu(II).     

New cadmium(II) halides modified by N-heterocyclic molecules

Under the solvothermal condition, the reaction of CdI₂, bpp and KI at pH = 8 afforded compound [CdI₂(bpp)] (bpp = 1,2-bis(4-pyridyl)propane) 1, while at the ambient conditions, the reactions of CdX₂, dabco and KX at pH = 4–5 produced compounds [H₂(dabco)][CdBr₄]·H₂O (dabco = 1,4-diazabicyclo[2,2,2]octane) 2 and [(Hdabco)CdI₃] 3. X-ray single-crystal diffraction analysis reveals that (i) compound 1 possesses a one-dimensional (1-D) zigzag chain structure. The large volume bpp molecule controls the Cd²⁺ ion to adopt a tetrahedral geometric configuration; (ii) both compounds 2 and 3 are mononuclear. Interestingly, in the same pH environments, dabco was in situ diprotonated in compound 2, while dabco was in situ monoprotonated in compound 3. The templating effect as well as the X⁻ ion maybe plays a key role in the protonated degree for dabco in an acidic environment. The photoluminescence analysis indicates that compound 1 emits the strong green light, which should be attributed to a combination of two types of charge transfers: the charge transfer between Cd²⁺ and I⁻; the charge transfer between Cd²⁺ and bpp.     

一种新的结构参数用于卤化物的QSPR研究

基于邻接矩阵和原子特征值（ｔｉ）建立一种新的结构参数（＾１Ｑ），它对无机分子具有良好的区分能力，并且计算简单，＾１Ｑ用于ＡＸｋ（ｋ＝１，２，３，４）型卤化物的标准生成焓、晶格能、反应截面等物理化学性质的相关性研究，获得了优于文献方法的结果。     

Transition metal complexes with pyrazole-based ligands. Part 28. Synthesis,structural, DFT and thermal studies of cadmium(II) halides and zinc(II) chloride complexes with 3,5-dimethylpyrazole-1-carboxamidine

The complex formation of 3,5-dimethylpyrazole-1-carboxamidinium nitrate, HL·HNO₃ with ammine complexes of cadmium(II) halides (Cl, Br, I) and zinc(II) chloride has been investigated under self-controlled reaction conditions. The complexes have been characterized by X-ray diffraction, FT-IR spectroscopy, thermal analysis and quantum chemical calculations. In the case of cadmium bromide and iodide salts, isostructural complexes with composition of [CdX₂(HL)₂] were formed. With CdCl₂ a binuclear octahedral [Cd₂(HL)₄(μ-Cl)₂](NO₃)₂ complex is obtained. Zinc(II) chloride with HL·HNO₃ gives [Zn(HL)₂Cl]NO₃, the zinc center exhibiting severely distorted five-coordinate stereochemistry, intermediate between an ideal trigonal bipyramid and a square pyramid. The course of complex formation as well as the thermal properties of the compounds has been explained using the HSAB principle. The assignment of the FT-IR spectra was supported by DFT computations.     

Chemistry and key structural features of oxyhydroxy-fluorides: relationships with the acidic character, thermal stability and surface area

The stability of Al, Cr and Fe hydroxy-fluorides MF_3−x(OH)_x which adopt the hexagonal-tungsten-bronze (HTB)-type structure has been discussed by considering the lability of water coordinated to metals from a kinetic point of view. Thus, in the case of Al or Fe compounds, the easy departure of water contributes to the stabilization of fluoride ions as well as isolated hydroxyl groups around the metal, leading to the formation of the HTB structure. The stabilization of the HTB structure with respect to another structural type, the pyrochlore, with a lower density, is governed by this kinetic feature as well as the ability of fluorinated salts used as precursors to attract hydroxyls. Al(III) and Fe(III) represent the strongest acidic cations and the associated HTB-type structure containing isolated OH groups can easily be stabilized. In the case of Cr, a mixture of pyrochlore and HTB-type structure is generally obtained. We have succeeded in preparing, using supercritical medium, new (Fe, Cr) oxyhydroxy-fluorides which exhibit edge-shared octahedra and large 1D tunnels. These compounds can be considered as potential candidates for acid catalysts.     

Bisthiourea: thermal and structural investigation

Bisthiourea derivatives 1,1′-(ethane-1,2-diyl)bis(3-phenylthiourea), 1,1′-(propane-1,3-diyl)bis(3-phenylthiourea), and 1,1′-(butane-1,4-diyl)bis(3-phenylthiourea) have been synthesized and characterized by IR, ¹H NMR, and ¹³C NMR. Suitable crystals of 1,1′-(propane-1,3-diyl)bis(3-phenylthiourea) were grown for single-crystal X-ray analysis and from the data it was observed that they organize into the P-1 space group. The thermal decomposition of these compounds has been studied by TG–DSC.     

Some novel hexa-coordinated cadmium Schiff base complexes: X-ray structure,Hirshfeld surface analysis,antimicrobial and thermal analysis

A series of cadmium (II) complexes with the general formula of CdLX₂, where X = Cl⁻, Br⁻, I⁻, SCN⁻ and N₃⁻ and L is a tetradentate N₄-donor Schiff base ligand; were synthesized by a sonochemical process as a simple, cost effective and environmentally friendly method. The organic ligand was obtained by condensation reaction of triethylenetetraamine (trien) and cinnamaldehyde. The characterization of coordination compounds was carried out by FT-IR, ¹HNMR, ¹³CNMR, UV–visible spectroscopies and then conductivity measurements. The crystal structure of the cadmium azide complex was determined by single crystal X-ray diffraction. This complex crystallizes in the monoclinic space group of C2/c. The cadmium ion is hexa-coordinated by four nitrogen atoms from the tetradendate Schiff base ligand and two terminal azide nitrogen atoms. The crystal packing and Hirshfeld surface analysis of the CdL(N₃)₂ complex indicates the essential role of intermolecular interactions related to azido groups in the formation of supramolecular structure. The thermal behavior of complexes was studied by TG/DTG analysis. Moreover, an antibacterial bioassay of the cadmium complexes has been performed in vitro against two gram-positive (Staphylococcus aureus and Bacillus subtilis) and two gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains. Furthermore antifungal activities of the compounds against two fungal strains of Aspergilus niger and Candida albicans were also investigated.     

A study of equilibrium between cadmium cyanide and alkali halides and thiocyanate by solubility measurements

Summary A study of the Cd(CN)₂ +x X^– [Cd(CN)₂X _x ] ^x– equilibrium (where X = Cl, Br or CNS) has been carried out at 18° and 38° by measuring the solubility of cadmium cyanide in potassium chloride, bromide and thiocyanate at various concentrations, and at a high ionic strength (6 M) maintained with sodium perchlorate to minimise the effect of activity coefficients. Equilibrium constants forx = 1 and 2 have been calculated and clearly favour the situation wherex = 1. H values for the dissociation of [Cd(CN)₂X]^– have also been calculated.