Some applications of thermal analysis to the coordination chemistry

The behaviour of complexes of the type MeD2I2 (Me=Co,D = acetylacetone or benzoylacetone,I = imidazole and derivatives in the course of the stepwise thermal degradation is different. In the case ofD = acetylacetone in the first step acetylacetone is split off. At D = benzoylacetone the decomposition starts with the partial elimination of the heterocyclic ligands.In-position unsubstituted nickelacyclic complexes from type (bipy)Ni(CH₂CH₂CH₂COO) decompose by a reductive elimination and separating of CO₂ forming a (bipy)Ni-intermediate. A single reductive decoupling is hindered by blocking up the-position.Opposite to the high thermal stability of the trimesityl aluminium the intermediates Almes₂Cl and AlmesCl₂ show with decreasing amounts of mesityl groups and increasing content of halogene, respectively, a significant decreasing thermal stability.The thermal degradation of nickelchelates of alkylsubstituted chinolin-8-ol starts with the dehydration followed by a different separation of the ligands as a function of the chain-length and the position of the substituents of the ligands.

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Zusammenfassung Das Zersetzung Verhalten der Komplexverbindungen vom Typ C0D2I2 (P = acetylaceton, Benzoylaceton;I = Imidazol oder Derivate) erfolgt stufenweise. Im Falle vonD = Acetylaceton erfolgt zuerst eine Eliminierung von Acetylaceton wärend beiD = Benzoylaceton zuerst ein Heteroligand eine Abspaltung erfährt.Bei einer unsubstituierten-Position von Nickelacyclen des Typs (bipy)Ni(CH₂CH₂CH₂COO) erfolgt eine thermisch induzierte-Hydrideliminierung unter Ringspaltung und Freisetzung von CO₂.Im Gegensatz zur hohen thermischen Stabilität des Trimesityl Aluminium erfahren die Zwischenverbindungen Almes₂Cl und AlmesCl₂ mit abnehmenden Mesityl- bzw. zunehmenden Chlorgehalt einen wessentlich früheren thermischen Zerfall. Bei zunehmenden Kovalenzgrad ist hier ein Einfluss der veränderten Polarisation anzunehmen.Der thermische Abbau der prinzipiell wasserhaltig kristallisierenden Nickelchelate von alkylsubstituierten Chinolin-8-ol beginnt jeweils mit der Dehydratisierung. In Abhängigkeit von der Kettenlänge und der Position der Substitution am Chinolin schliesst sich der thermische Abbau der Chelatliganden ein- bzw. mehrstufig an.

     

Influence of conjugated nitrogenous bases on the spectra and structure of mixed-ligand nickel(II) chelates containing β-diones

The infrared and electronic excitation spectra of a series of new nickel(II) chelates containing an-diimine (or nitrogenous base, enR) and the anion of a-dione (1,3-ketoenol or 1,3-ketoester,H) were obtained in the solid state and in solution. The composition and the overall structure of the new chelates in the solid state depends on ligand concentration, the substituents within the-dionato moiety and the counterion present. The IR and electronic excitation spectra of [Ni(enR)₂ ]NO₃ and [Ni(enR)(O₂NO)] indicate, in conjunction with other physicochemical measurements, bidentate coordination of the ligands, while the spectral shifts reveal replacement of the (O,O)nitrato group by basic solvents. The existence of the nickel(II) in an octahedral environment is confirmed by an X-ray structure analysis of [Ni(dpamH)₂acac]NO₃ · CH₃OH (monoclinic, space groupP2_l/n, a=17.296(1),b=7.462(1),c=21.604(3) å,=95.65(1),Z=4, R=0.0534,Rw=0.0600), where dpamH denotes the 2,2-dipyridylamine.     

Synthesis, Crystal Structure, and Magnetic Properties of the Two-Dimensional Nickel(II) Complex via Covalent and Hydrogen Bonds: [Ni(L)(H2O)2][Ni2(L)(NTA)2]ċ6H2O (L = 3,14-di-methyl-2,6,13,17-tetra- azatricyclo[14,4,01.18,07.12]docosane, NTA = Nitrillotriacetate)

A new compound [Ni(L)(H₂O)₂][Ni₂(L)(NTA)₂]6H₂O (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]- docosane, NTA = nitrillotriacetate) was prepared and its structure was determined by the X-ray diffraction method. Complex 1 crystallizes in the monoclinic space group P2_1/c with a = 11.217(2) , b = 18.048(5) , c = 15.393(3) , = 90.78(2)°, V = 3115.9(12) ³, and Z= 2, Each nickel atom in complex 1 has a distorted octahedral coordination geometry with an inversion center. Magnetic susceptibility measurement showed a weak intramolecular antiferromagnetic interaction between two Ni(1) and Ni(2) centers with a J value of -0.93(1) cm^–1. The intermolecular hydrogen-bonding interaction gives rise to a two-dimensional network.     

On the thermal decomposition of NiSO4.nH2O (n=7,6,4,1) and of their deuterated analogs

The DTA method has been used in studying the thermal dehydration and decomposition of NiSO₄.nH₂O, accordingly of NiSO₄.nD₂O, (atn=7, 6, 4, 1) in a temperature interval of 20 to 900°C, at a heating rate of 10 deg/min. The endoeffects observed show in all cases partial dehydration to monohydrate and evolution of the last molecule of hydrate water at a high temperature T _max -360°C for the hydrates and T _max 360-335°C for the deuterates. At NiSO₄.6H₂O (6D₂O) and NiSO₄.4D₂O there occurs stepwise dehydration before the monohydrate as well. Decomposition of the anhydrous NiSO₄ takes place at higher temperature which depends on whether it had been obtained from the respective deuterate ordinary hydrate. The one obtained from the deuterate undergoes decomposition at relatively lower temperature.

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Zusammenfassung Mittels DTA wurde im Temperaturbereich von 20 bis 900°C die thermische Dehydratation und Zersetzung von NiSO₄.nH₂O sowie NiSO₄ nD₂O (mitn=7,6,4,1) bei einer Aufheizgeschwindigkeit von 10 deg/min untersucht. Ende-Effekte weisen in allen Fällen auf eine teilweise Dehydratation zum Monohydrat hin. Das letzte Molekül Kristallwasser wird bei einer höheren Temperatur, im Falle der Hydrate beiT _max 360°C, im Falle der Deuterate beiT _max 360-335°C abgegeben. Bei den Verbindungen NiSO₄6H₂O (6D₂O) sowie NiSO₄.4D₂O verläuft auch eine stufenweise Dehydratation vor Erreichen der Monohydratstufe. Die Zersetzung von wasserfreiem NiSO₄ verläuft bei höheren Temperaturen, deren Wert davon abhängt, ob die Verbindung aus Deuterat oder Hydrat entstand. Das aus Deuteraten erhaltene zersetzt sich schon bei relativ geringeren Temperaturen.

     

Zur Kenntnis von funktionellen Si-Heterocyclen

Zusammenfassung -Sila-äthylamine mit zwei Funktionen am Siliciumatom wurden in Form von 2-Sila-2-alkoxy-morpholinen dargestellt. Bei der Hydrolyse gehen sie unter Spaltung der Si-O-C-Bindungen am und im Ring und teilweise auch unter Spaltung der Si-C-Bindung im Ring in wenig definierte Polysiloxane über. Quaternäre-Sila-äthylamine mit zwei Funktionen am Siliciumatom gehen mit Wasser unter Erhaltung der Si-C-Bindungen in kurzkettige Polysiloxandiole über.

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Summary -Sila-ethylamines with two functional groups on silicon have been synthesized as 2-sila-2-alkoxymorpholines. Hydrolysis of these cyclics leads to cleavage of Si-O-C-bonds on and within the ring, partly to cleavage of Si-C-bonds within the ring, resulting in ill-defined polysiloxanes. Analogous quaternary derivatives retain their Si-C-bonds in aqueous medium and form low molecular polysiloxanediols.

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Herrn Prof. Dr.W. Noll zum 60. Geburtstag gewidmet.     

Conformational studies of basic poly (α-amino acid)s in reversed micelles

The conformation of various basic poly (-amino acid)s was investigated by CD measurements in aqueous solutions containing bis (2-ethylhexyl)sodium sulfosuccinate (AOT) as well as in the AOT reversed micelles. The addition of AOT into an aqueous solution of poly(L-lysine) induces the conformational transition from coil to ordered structure, followed by aggregation. On the other hand, poly(L-lysine) assumes-structure in the reversed micelles at low w_ovalue (w_o=[H₂O]/[AOT]). Similarly to poly(L-lysine), poly(L-ornithine) takes an ordered structure in the aqueous solution containing AOT and-structure in the reversed micelles. In this case, however, these ordered structures are not so stable, compared with that of poly(L-lysine). Poly(L-arginine) undergoes the conformational transition from coil to helix by addition of AOT into the aqueous solution. Further addition of AOT allows transformation into-structure. Copoly(L-lysyl-L-leucine) with 63% leucine residue was shown to take a stable helical conformation even in pure water. In the reversed micelles, however, this ordered structure is significantly changed probably because the hydrophobic interaction among the leucyl residues is lowered in the reversed micelles.     

MO-LCAO-Berechnungen an schwefelhaltigen π-Elektronensystemen

Zusammenfassung Mercaptobenzol wird als ein 8-Elektronensystem mit sieben Basisorbitalen nach einem SCF-CI-Verfahren in Pariser-Parr-Pople-NÄherung behandelt. Alle Einzentrenabsto\ungsintegrale werden gleichgesetzt ( _CC=_SS=10,84 eV) und die Zweizentrenabsto\ungsintegrale nach der Mataga-Nishimoto-Beziehung ermittelt. An Hand des UV-Absorptionsspektrums von Mercaptobenzol zwischen 155 und 300 m werden für U _S=21 eV und _CS=0,5 _CC empirisch abgeleitet. Die Berechnungen an Mercapto- und Methylmercaptobenzol erlauben neben einer Interpretation der UV-Spektren Aussagen über Ionisationseigenschaften und die Ladungsverteilungen, die in guter übereinstimmung mit dem Experiment stehen. Die Brauchbarkeit der vorgeschlagenen Parameter wird durch Berechnungen an 1,2-, 1,3- und 1,4-Dimercaptobenzol, 1- und 2-Mercaptonaphthalin und 9-Mercaptoanthracen nachgewiesen.

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Mercaptobenzene is treated as an 8-electron-system with seven basis orbitals according to an SCE-CI-method in the Pariser-Parr-Pople approximation. All of the one-center repulsion integrals were assumed to be the same ( _CC=_SS=10.84 eV) and the two-center repulsion integrals were determined according to the Mataga-Nishimoto-relation. Values of U _s =21 eV and _CS=0.5 _CC were derived empirically from the UV-absorption spectrum of mercaptobenzene in the region 155–300 m. The calculations on mercapto- and methylmercaptobenzene, besides allowing an interpretation of the UV-spectra, give predictions of ionization properties and charge distributions showing good agreement with experiment. The usefulness of the suggested parameters is shown with calculations on 1,2-, 1,3- and 1,4-dimercaptobenzene, 1- and 2-mercaptonaphthalene and 9-mercaptoanthracene.

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Résumé Mercaptobenzène est traité comme un système de 8 électrons avec sept orbitales de base dans une méthode SCF-CI en approximation PPP. Les valeurs de U _S=21 eV et _CS=0,5 _CC sont obtenues à l'aide du spectre d'absorption U.V. Les calculs en Mercapto- et Méthylmercaptobenzene permettent aussi bien une interprétation des spectres U.V. comme des indications sur la ionisation et la distrubation de charge qui sont en bonne relation avec les experimentaux. Avec les paramètres proposés en recoit aussi pour 1,2,1,3-, 1,4- Dimercaptobenzène, 1- et 2-Mercaptonaphtaline et Mercaptoanthracène des résultats valables.

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X. Mitteilung: Fabian, J.: Wiss. Z. Techn. Univ. Dresden 1967. (Im Druck.)

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Herrn Dr. R. Zahradník (SAV Prag), der diese Arbeit ma\geblich gefördert hat, danken wir für die Durchsicht des Manuskriptes. Für die überlassung der Dimercaptobenzole sind wir Herrn Dr. J. Morgenstern (TU Dresden) sehr verbunden.     

Quinolinic acid as a reagent for the gravimetric and volumetric estimation of palladium

Summary Like -amino-picolinic acid, quinolinic acid behaves as a highly selective reagent for palladium with which it forms a complex of composition Pd(C₇H₄O₄N)₂. The complex being very stable is precipitated from solutions with an acidity of 0.25 N to a maximum p_H of 2.1 and thus is separated from all the common ions and other platinum metals except copper which, however, can be kept in solution in presence of EDTA. The palladium complex is either weighed after drying or dissolved in a standard potassium cyanide solution which is later back titrated with silver nitrate solution.     

C–H· π Interaction and N·H–O Hydrogen Bonding in the Chair-like p-tert-Butylcalix[8]arene Complex Including Four Pyridine Molecules

Crystal structure analysis shows that the p-tert-butylcalix[8]arene host and its four pyridine guests sit around an inversion center in the P2₁/c crystal lattice. The monoclinic cell parameters and its volume are: a = 19.617(4), b = 9.912(2), c = 25.178(5) , = 101.03(3)°, V =4805.27(17) ³. For Z = 2 and Mw = 1614.18, the calculated density Dcalc = 1.116 g/cm³. A host calixarene molecule includes four pyridine guests in two different ways: by hydrogen bonding and by possible C–H· interaction between the molecules. The hydrogen bonding drives the host macrocycle into a chair-like conformation.     

Synthesis of pyrylium salts by condensation of Β-chlorocinnamaldehydes with carbonyl compounds

A method is proposed for the synthesis of unsymmetrical unsubstituted pyrylium salts by condensation of -chlorocinnamaldehydes with methyl and methylene ketones and -dicarbonyl compounds in the presence of HClO₄ or Lewis acids. The probable scheme of the reaction is examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1031–1035, August, 1974.     

Hydrate inclusion compounds

There are three general classes of hydrate inclusion compounds: the gas hydrates, the per-alkyl onium salt hydrates, and the alkylamine hydrates. The first are clathrates, the second are ionic inclusion compounds, the third are semi-clathrates. Crystallization occurs because the H₂O molecules, like SiO₂, can form three-dimensional four-connected nets. With water alone, these are the ices. In the inclusion hydrates, nets with larger voids are stabilized by including other guest molecules. Anions and hydrogen-bonding functional groups can replace water molecules in these nets, in which case the guest species are cations or hydrophobic moieties of organic molecules. The guest must satisfy two criteria. One is dimensional, to ensure a comfortable fit within the voids. The other is functional. The guest molecules cannot have either a single strong hydrogen-bonding group, such as an amide or a carboxylate, or a number of moderately strong hydrogen-bonding groups, as in a polyol or a carbohydrate.The common topological feature of these nets is the pentagonal dodecahedra: i.e., 5¹²-hedron. These are combined with 5¹²6²-hedra, 5¹²6³-hedra, 5¹²6⁴-hedra and combinations of these polyhedra, to from five known nets. Two of these are the well-known 12 and 17 Å cubic gas hydrate structures,Pm3n, Fd3m; one is tetragonal,P4 ₂/mnm, and two are hexagonal,P6 ₃/mmc andP6/mmm. The clathrate hydrates provide examples of the two cubic and the tetragonal structures. The alkyl onium salt hydrates have distorted versions of thePm3n cubic, the tetragonal, and one of the hexagonal structures. The alkylamine hydrate structures hitherto determined provide examples of distorted versions of the two hexagonal structures.There are also three hydrate inclusion structures, represented by single examples, which do not involve the 5¹²-hedra. These are 4(CH₃)₃CHNH₂·39H₂O which is a clathrate; HPF₆·6H₂O and (CH₃)₄NOH·5H₂O which are ionic-water inclusion hydrates. In the monoclinic 6(CH₃CH₂CH₂NH₂)·105H₂O and the orthorhombic 3(CH₂CH₂)₂NH·26H₂O, the water structure is more complex. The idealization of these nets in terms of the close-packing of semi-regular polyhedra becomes difficult and artificial. There is an approach towards the complexity of the water salt structures found in the crystals of proteins.     

π-Interaction in metal Β-ketoenolates

The available data (supplemented where necessary) on the electronic, nuclear magnetic resonance and vibrational spectra of metal -ketoenolates has been analysed to assess the relative contributions of donor and acceptor metal-ligand -bonding in the first transition period metal (III) -ketoenolates. The effects of the metal ion and the ligand substituent on the -interaction in the -ketoenolate ring are discussed in terms of established theoretical concepts.

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Zusammenfassung Die bekannten Daten (ergÄnzt, falls notwendig) der elektronischen und kernmagnetischen Resonanz sowie der Schwingungsspektren von Metall--ketoenolaten wurden analysiert, um die relativen BeitrÄge von Donor- und Akzeptor (Metall-Ligand) -Bindung in Metall(III)ketoenoIaten der ersten übergangsperiode zu ermitteln. Die Einwirkung des Metallions und des Ligandsubstituenten auf die -Bindung im -Ketoenolatring werden diskutiert auf der Grundlage von bekannten theoretischen Prinzipien.

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Résumé L'examen des résultats antérieurement publiés (supplementés ou nécessaire) des spectres électroniques, résonance nucléaire magnétiques et vibrationnel nous a amenés à préciser les contributions relatifs de liaison- donneur et accepteur entre métal et ligand de la première période transitionelle métal(III) -kétoénolates. Les effects de l'ion métallique et du ligand substituent exercés sur l'interaction- dans le noyau -kétoénolate sont discutés selon les idées théoriques déjà établies.

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This work was supported by University of Cape Town and C.S.I.R. Research Grants. We thank the National Institute for Metallurgy for a bursary (to R.D.H.).     

Synthesis of 2-functionally substituted oxazolines and oxazolidines from methyl bromopropiolate and Β-amino alcohols

The reaction of methyl bromopropiolate with -amino alcohols containing a primary amino group generally results in the formation of 2-(methoxycarbonylmethyl)-²-1,3-oxazolines, while in the reaction with N-methyl- and N,N-dimethyl-substituted -aminoalcohols, 2-(methoxycarbonylmethylene)-1,3-oxazolidines, or their salts are formed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 406–409, March, 1991.     

Formation of ultra-thin films consisting of proteins or polysaccharides and syndiotactic-rich poly-vinyl alcohol mixtures adsorbed at air-solution interface

Ultra-thin films of syndiotactic-rich poly-vinyl alcohol (s-PVA) with several proteins and polysaccharides were prepared by the bubble and frame methods using a mixed dilute aqueous solution (1.5g/dL).The mixed amount of-cyclodextrin (-CD) was the largest among these proteins and polysaccharides giving a weight ratio (-CD/s-PVA) of 1. The ratios of silk fibroin(SF), lysozyme, pepsin, and pectin tos- PVA were 0.58, 0.40, 0.35, and 0.35, respectively. For the-CD/s-PVA and SF/s-PVA blend thin films, the phase separation was observed.     

Carbolines

4-Substituted 3, 4-dihydro--carbolines (X–XVI) were obtained by the Beckman rearrangement of oximes of -(indolyl-3)ketones (I–IV, IX) under the action of phosphorus pentachloride in nitrobenzene. 3, 4-Dihydro--carbolines were converted into -carbolines (XV–XVII) on heating with Brown's palladium catalyst in ethylene glycol. Oximes containing the aryl group react on treatment with p-toluene sulfochloride in pyridine with the formation of the arilides of -(indolyl-3)propionic acids.For preliminary report, see [18].     

Investigation of the influence of a sulfur atom on the mobility of the hydrogen atoms in a methylene group of some heterocyclic compounds

The action of dicyclohexylcaibodiimide on 2-benzimidazolylthioacetic,-(2-benzimidazolylthio)propionic,-(2-benzimidazolyl)propionic and 2-benzimidazolylacetic acids has given the anhydro derivatives of these acids. It has been shown that the hydrogen atoms in the methylene group of anhydro-2-benzimidazolylthioacetic acid have the highest mobility.     

π-Electron correlation in alternant hydrocarbons: Bondorder-bondlength relation,force constants and the spectroscopic,vibrational and thermochemical Β-values

The applicability of empirical relations between bondorders and bondlengths is shown to be subject to some restrictions which are of considerable importance in the calculation of force constants from MO-theories. The consequent application of a suggested correction leads to a new (r)-relation from which correct predictions of both UV-spectra and vibrational force constants may be obtained. Force constant calculations from thermochemical parameters are shown to be unreliable; a discussion of the thermochemical evaluation of suggests a number a possible causes of the limitations of its applicability.

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Zusammenfassung Es wird gezeigt, da\ der theoretische Bewcis für die Existenz einer Beziehung zwischen P und r in konjugierten Kohlenwasserstoffen nicht ohne weiteres als Begründung für empirische P(r)-Funktionen verwendet werden soll. Aus der Verfeinerung der Theorie folgt eine neue empirische Beziehung zwischen und r, die in Gegensatz zu Älteren Funktionen solcher Art bei Berechnungen, nicht nur von UV-Spektren, sondern auch von Kraftkonstanten erfolgreich ist. Dahingegen können die bisher vorgeschlagenen thermochemischen -Werte nicht zur Berechnung der Kraftkonstanten verwendet werden. Eine Diskussion des thermochemischen Rechenverfahrens ergibt einige mögliche Ursachen der beschrÄnkten Anwendbarkeit der auf diesem Wege gefundenen -Werte.

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Résumé Une revision critique de la preuve de l'existence d'une relation entre P et r dans les hydrocarbures conjugués conduit à la conclusion que cette preuve est valable seulement pour une courbe théorique qui peut différer assez fortement d'une courbe empirique. En introduisant les corrections nécessaires nous arrivons à une nouvelle relation entre et r, qui peut Être appliquée avec succès dans les calculations des spectres UV aussi bien que des constantes de force. Par contre une évaluation correcte des constantes de force est impossible si l'on emploie les valeurs thermochimiques de proposées jusqu'à présent; il apparait que ce résultat négatif doit probablement Être attribué à quelques simplifications qui font part de la méthode thermochimique.

     

Investigation of conjugation in the Si-O-C-C-N system by nuclear magnetic resonance

The proton-magnetic-resonance spectra were investigated for 19 -aminoethoxysilanes in the R_4-nSi(OCH₂CH₂NR₂)_n and R_3-m(CH₂CH₂OR)_m series, where R=CH₃, C₂H₅, or C₆H₅; R=H, CH₃, C₂H₅, or Si(CH₃)₃; and the values of n and m are 1–4 and 1–3, respectively. In the Si-O-C-C-N system the effect of substituents at the nitrogen or silicon atoms is transmitted either by conjugation in the chain or, when the conjugation is broken, by an induction mechanism.     

EPR spectra and characteristics of metal-ligand bond in complexes of divalent copper with some amino acids

Electron paramagnetic resonance spectra were obtained in low-temperature glasses for a series of copper complexes with amino acids: glycine, - and -alanine, valine, leucine, histidine, serine. The ionicity coefficients ² and ₁ ² of the metal-ligand bond were calculated from the spin Hamiltonian constants and from optical data. The results are compared with the stability of the investigated complexes.     

Synthesis of methylamides of O-(2-acetamido-2-desoxy-Β-D-glucopyranosyl)-N-acetylserine and O-(2-acetamido-2-desoxy-Β-D-glucopyranosyl)-N-acetylthreonine

Conclusions The oxazoline method was used to synthesize the methylamides of O-(2-acetamido-2-desoxy--D-glucopyranosyl)-N-acetylserine and O-(2-acetamido-2-desoxy--D-glucopyranosyl)-N-acetylthreonine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 697–699, March, 1975.