bluuebunny/crossref_metadata_2025 huggingface dataset:
Übergangsmetallketen-Verbindungen, XIX [1]. Umwandlung von η2 -Ketenyl-in η2 -Alkinkomplexe mit Lewis-Säuren / Compounds of Transition Metal Ketenes, XIX [1]. Conversion of η2 -Ketenyl-into η2 -Alkyne Complexes Using Lewis Acids
Authors: Kreißl Fritz R. , Sieber Werner J. , Wolfgruber Mathias
Published: February 2015

Carbonyl(η5 -cyclopentadienyl)(η2 -ketenyl)trimethylphosphine tungsten complexes add Lewis acids to the ketene oxygen atom with concomitant conversion of the η2 -ketenyl into an η2 -alkyne ligand.
Gehinderte Ligandbewegungen in Übergangsmetall-Komplexen, XXI [1]. Isomeric und Dynamik von cis-Dicarbonyl-bis(η4 -2-methyl-1.3-butadien)wolfram(0) / Hindered Ligand Movements in Transitionmetal Complexes, XXI [1]. Isomerism and Dynamics of cis-Dicarbonyl-bis(η4 -2-methyl-1,3-butadiene)tungsten(0)
Authors: Kreiter Cornelius G. , Özkar Saim
Published: February 2015

cis-Dicarbonyl-bis(2-methyl-1,3-butadiene)molybdenum(0) (1) and -tungsten(0) (2) were prepared photochemically from tricarbonylmesitylene-molybdenum(0) and aceto-nitrile-pentacarbonyl-tungsten(0), respectively, as thermolabile yellow oils. 2 is obtained as a mixture of two diastereomeric pairs of enantiomers 2a (2a') and 2c (2c'). From 1H and 13C NMR spectroscopic data 2 a (2a') is shown to have C2 symmetry, whereas 2 c (2c') is asymmetric. The NMR signals of 2 c (2 c') are temperature dependent due to an intramolecular 2c⇄2c'-isomerization (⊿G≠250 = 47 kJ · mol-1). A trigonal prismatic transi-tion state with Cs symmetry explains the D-NMR spectroscopic results. The NMR signals of 2 a (2a') are temperature dependent, too. This is taken as evidence for a ligand movement which brings 2a (2a') on the way to a third diastereomeric form 2b' (2b), with no detectable population. The molybdenum complex 1 forms only the isomers la (la') with C2 symmetry.
Über das [C7H7Fe2(CO)5]--Anion (C7H7 = Cycloheptatrienyl) / About the [C7H7Fe2(CO)5]--Anion (C7H7 = Cycloheptatrienyl)
Authors: Moll Matthias , Behrens Helmut , Popp Werner , Liehr Günther , Fehlhammer Wolf Peter
Published: February 2015

The extremely unstable anionic complex [C7H7Fe2(CO)6]- (C7H7 = cycloheptatrienyl) which decomposes in polar solvents under CO elimination to give [C7H7Fe2(CO)5]- can be prepared by deprotonation of C7H8Fe2(CO)6 (C7H8 = cycloheptatriene) with NaN(SiMe3)2 in C6H6.The NMR spectra of [C7H7Fe2(CO)5]- show the highly fluctional character of this anion in solution. The X-ray structural parameters of Ph4As[C7H7Fe2(CO)5] (space group P21/n) can be interpreted in terms of a rotation of the tub shaped C7H7 ring against the CO bridged Fe2(CO)5 fragment in the solid state. Consequently, each iron atom is alternatingly η3 -or η4-coordinated to the allyl anion and the diene part, respectively, of the anionic 8π system of the cycloheptatrienyl ring.
Beiträge zur Chemie des Bors, 137 [1]. Über eine einfache Synthese eines Amino-imino-borans und seiner Addukte mit Bortrichlorid und Bortribromid / Contribution to the Chemistry of Boron, 137 [1]. A Convenient Synthesis of an Amino-Imino-Borane and its Adducts with Boron Trichloride and Boron Tribromide
Authors: Nöth Heinrich , Weber Siegfried
Published: February 2015

The amino-imino-borane (1) has been synthesized in high yield by a three step reaction. Pure 1 dimerizes fairly rapidly but can be stored as a monomer in solution for several weeks. It adds BCl3 and BBr3 with haloboration. The resulting diborylamines, 6 and 7, form a four membered cyclic internal coordination compound. The structure of the corresponding bromo derivative has been determined by X-ray crystallography. Its B2N2- ring is planar and contains four significantly different BN bonds. One of these is the shortest BN bond length yet observed for tricoordinated boron and nitrogen atoms (134 pm). Considering bond lengths the adduct can be looked upon as a coordination compound of an aminoborane with an iminoborane.
Metallorganische Lewis-Säuren, XIV [1]. Ethylen-verbrückte Mangan- und Rheniumcarbonyle; Tieftemperatur-Röntgenstrukturanalyse von (OC)5ReCH2CH2Re(CO)5 / Organometallic Lewis Acids, XIV [1]. Ethylene Bridged Manganese and Rhenium Carbonyls; Low Temperature X-Ray Structure of (OC)5ReCH2CH2Re(CO)5
Authors: Raab Klaus , Nagel Ulrich , Beck Wolfgang
Published: February 2015

The tetrafluoroborato complexes (OC)5MFBF3 (M = Mn, Re) which are obtained by methyl abstraction from (OC)5MCH3 using Ph3CBF4 react with ethylene or propene at room temperature and 1 bar to give [(OC)5M(alkene)]+ BF4-. By nucleophilic addition of the carbonylmetalates [M(CO)s] -(M = Mn, Re) to the coordinated alkene in these cationic complexes [(OC)5M(alkene)]+ the alkene bridged complexes (OC)5MCH2CH(R)M(CO)5 (M = Mn, Re; R = H, Me) are formed. Also the mixed-metal complex (OC)5MnCH2CH2Re(CO)5 has been isolated. According to an X-ray structure at low temperature (OC)5ReCH2CH2Re(CO)5 can be considered as a dimetal substituted ethane with a carbon-carbon distance of 152 pm.
Überführung von Triazaphospholen in Diazaphosphole durch Acetylenaddition/Nitrileliminierung [1] / Conversion of Triazaphospholes into Diazaphospholes by Acetylene Addition/Nitrile Elimination [1]
Authors: Schmidpeter Alfred , Klehr Hubert
Published: February 2015

Acetylene di-and (less easily) monocarboxylic esters replace nitriles from the 4,5-position of 1,2,4,3-triazaphosphole rings to give carboxyl derivatives of 1,2,3-diazaphospholes, presumably by a cycloaddition/cycloreversion mechanism. In cases with a mobile N-substituent alternatively the loss of N2 seemed feasible, but was normally not observed.
Hydrido-Silyl-Komplexe, IV [1]. Strukturelle Änderungen in Hydrido-Silyl-Komplexen infolge Si-H-Wechselwirkung; Strukturvergleich von (π-CH3C5H4)(CO)2Mn(H)SiCl3 und trans-(π-CH3C5H4)(CO)2Mn(SiCl3)2 / Hydrido Silyl Complexes, IV [1]. Structural Changes in Hydrido Silyl Complexes Due to Si-H Interaction; Comparison of the Structures of (π-CH3C5H4)(CO)2Mn(H)SiCl3 and trans-(π-CH3C5H4)(CO)2Mn(SiCl3)2
Authors: Schubert Ulrich , Ackermann Klaus , Kraft Gertraud
Published: February 2015

The main difference between the structures of MeCp(CO)2Mn(H)SiCl3 (1) and MeCp(CO)2Mn(SiCl3)2 (2) is that in 1 the SiCl3 ligand is tilted relative to the Mn-Si vector, due to Mn-H-Si three-center two-electron bonding. Mn-Si: 225.4(1) in 1, 232.0(2) pm in 2. Comparison of the structures of MeCp(CO)2Mn(H)SiR3 complexes shows that the Mn-Si distance and the tilt angle of the SiR3 group increases as Si-H interaction increases. A stereochemical pathway of the oxidative addition of HSiR3 to the CpMn(CO)3 fragment is suggested.
Fünffach koordinierte Zirkonium(IV)-Komplexe mit der (η-C5H5)2ZrIV-Baueinheit. Die Struktur von (η-C5H5)2Zr(CF3SO3)2(THF) / Five Coordinate Zirconium(IV) Complexes with the (η-C5H5)2ZrIV Unit. The Structure of (η-C5H5)2Zr(CF3SO3)2(THF)
Authors: Thewalt Ulf , Lasser Wiltraud
Published: February 2015

Bis(η-cyclopentadienyl)tetrahydrofuran-bis(trifluoromethanesulfonato)zirconium(IV), (η-C5H5)2Zr(CF3SO3)2(THF), has been prepared by reaction of (η-C5H5)2ZrCl2 with AgCF3SO3 in tetrahydrofuran. Crystal data: Orthorhombic, Pnma, a = 15.890(5), b = 13.319(4), c = 10.376(3) Å, Z = 4. An X-ray analysis shows that the complex has a five-coordinate bent metallocene structure. The geometry of the (η-C5H5)2Zr moiety (length of the vectors between Zr and the C5 ring centroids: 2.203 and 2.214 Å, angle between these vectors: 128.1°, angle between C5 ring normals: 127.8°) agrees with that of four-coordinate (η-C5H5)2ZrX2 compounds. The metal bonded O atoms of the three additional ligands lie nearly in a plane bisecting the plane of the C5H5 ligands, the THF group being symmetrically flanked by CF3SO3 ligands.
Photochemistry of Osmium-Carbyne Complexes
Authors: Vogler Arnd , Kisslinger Josef , Roper Warren R.
Published: February 2015

Upon charge transfer (Os to carbyne) excitation the carbyne complexes Os(CPh)(CO)(PPh3)2Cl and [Os(CPh)(CO)2(PPh3)2]+ with Ph = C6H5 are converted to the carbene complex Os(CHPh)(CO)(PPh3)2Cl2 in solutions containing HCl. It is suggested that the relaxed CT state can be described as square-pyramidal Os(II) complex containing a bent carbyne ligand which carries a lone pair at the coordinating carbon atom. Product formation occurs by the addition of a proton to the carbyne ligand and by attaching a chloride to the osmium completing an octahedral coordination. The cationic carbene complex thus formed is apparently not stable but undergoes a substitut ion of a CO ligand by chloride.
Die Reduktion von Bleidioxid-Synthese-Anoden / Reduction of Lead Dioxide Synthesis Anodes
Authors: Wabner Dietrich , Tillmetz Werner
Published: February 2015

Abstract The electrochemical and chemical reduction of α-and β-lead dioxide synthesis anodes in sulfuric or nitric acid, resp., are investigated. The processes are elucidated by scanning electron microscope pictures. For the reduction of lead dioxide to lead sulfate a solution-precipitation mechanism is confirmed. This result fits very well with present day battery research. Reduction as well as re-oxidation result in an enlargement of active surface. Therefore temporary reduction has a decisive influence on the potential characteristics of lead dioxide anodes. Conclusions are given for their application in electrochemical syntheses.
RS-verbrückte Carbonyl-Wolfram-Komplexe / RS-Bridged Carbonyl Tungsten Complexes
Authors: Winter Andreas , Scheidsteger Olaf , Huttner Gottfried
Published: February 2015

Photochemical reaction of thiols RSH or disulfides RSSR with W(CO)6 gives dinuclear complexes [W(CO)4(μ2-SR)2]2 and trinuclear open chain compounds (CO)4(μ2-SR)2W(CO)2(μ2-SR)2W(CO)4. Syntheses and properties, including solid state structures as determined by X-ray methods are described.
Die Kristallstruktur von [Na(H2O)3]2TeBr6, ein Hydrat mit Ketten aus flächenkondensierten Na(H2O)6-Oktaedern / The Crystal Structure of [Na(H2O)3]2TeBr6, a Hydrate with Chains of Face-Sharing Na(H2O)6 Octahedra
Authors: Abriel Walter
Published: February 2015

Using 293 K diffractometer intensity data the structure of [Na(H2O)3]2TeBr6 has been determined by single crystal X-ray technique and refined to a final Rw of 0.048. The crystals are monoclinic (space group C2/m) with a = 13.039(4) Å, b = 10.899(8) Å, c = 6.838(3) Å, β = 115.89(2)° and Z = 2. The structure contains infinite chains parallel [001] built up by face-sharing Na(H2O)6-octahedra. Isolated TeBr6
2- octahedra between these chains represent the anion part of the structure, which can be regarded as a packing of layers based on a 33.42.-net consisting of oxygen and bromine atoms
X-Ray Structural Analyses of Cyclodecasulfur (S10) and of a Cyclohexasulfur-Cyclodecasulfur Molecular Addition Compound (S6 · S10) [1]
Authors: Steudel Ralf , Steidel Jürgen , Reinhardt Richard
Published: February 2015

Low temperature X-ray structural analyses of monoclinic single crystals of S10 and S6 · Si10 (prepared from the components) show that the cyclic S10 molecule exhibits the same D2 conformation in both compounds with bond distances between 203.3 and 208.0 pm, bond angles (α) between 103 and 111°, and torsional angles (τ) between 73 and 124°. The S6 molecule (site symmetry Ci) in S6 · S10 is very similar to the one in pure S6 (dSS = 206.2 pm, α= 103°, τ = 74°). All intermolecular interactions are of van-der-Waals type. The Raman spectrum of S6 · S10 can be explained by a superposition of the S6 and S10 spectra
Synthese von Silicium-Phosphor-Ringen - Struktur eines cis-2.2.4.4-Tetrakis(silylamino)-1.3-diphospha-2.4-disilacyclobutans / Synthesis of Silicon-Phosphorus-Rings - Structure of a cis-2,2,4,4-Tetrakis(silylamino)-1,3-diphospha-2,4-disilacyclobutane
Authors: Klingebiel Uwe , Vater Norbert , Clegg William , Haase Martin , Sheldrick George M.
Published: February 2015

Fluorosilylphosphanes of the type R2SiFPHR′ (R = CHMe2, CMe3, NMeSiMe3; R′ = H, C6H5; 1-4) are obtained in the reaction of difluorosilanes with lithiated phosphanes in a molar ratio 1:1. Diphosphasilanes (5, 6) and a difluorosilylphosphane (7) are isolated as by-products. 1-4 react with n-C4H9Li to give cyclic silylphosphanes, LiF, and C4H10 (8-11). Dilithiated 5 reacts with F2PN(CMe3)SiMe3 to form of a four-membered SiP3-ring 12. The 31P NMR spectra of 9 and 11 show signal coalescence for the cis-and trans-isomers at room temperature. The crystal structure of the cis-isomer of 11 has been determined. The substituted ring 13 is prepared in the reaction of lithiated 9 and Me2SiF2
Tetraschwefel-pentastickstoff-fluorid / Tetrasulfur-pentanitrogen Fluoride
Authors: Isenberg Wilhelm , Mews Rüdiger , Sheldrick George M.
Published: February 2015

The preparation of S4N5F by fluoride ion addition to the S4N5
+-cation in liquid SO2 is described. The structure of the fluoride was determined from single crystal data. The mechanism for the formation of S4N5F and the stability of possible isomers is discussed on the basis of MNDO/1 calculations
Kristallstruktur und Schwingungsspektren des Thalliumhexathiometadiphosphates Tl2P2S6 / Crystal Structure and Vibrational Spectra of Tl2P2S6
Authors: Wibbelmann Claus , Brockner Wolfgang , Eisenmann Brigitte , Schäfer Herbert
Published: February 2015

Tl2P2S6 crystallizes in the orthorhombic system, space group Immm, Z = 2 with the lattice constants

a = 793.2(4) pm, b = 689.2(4) pm, c = 901.9(5) pm.

In the structure there are discrete P2S6
2- -anions. The P2S6
2- -ion was found to be a hexa-thiometadiphosphate group where the two P atoms are linked by two S bridges.

Far infrared, infrared and Raman spectra of this compound have been recorded. The observed frequencies are assigned on the basis of P2S6
2- units with D2h symmetry in analogy to the isoelectronic Al2Cl6
Ba4Ga4S10, eine neue Verbindung mit einem Ga4S10
8- -Adamantankäfig / Ba4Ga4S10, a New Compound with an Adamantane Like Ga4S10
8- Cage
Authors: Eisenmann Brigitte , Jakowski Mareike , Schäfer Herbert
Published: February 2015

The new compound Ba4Ga4S10 crystallizes in the monoclinic system, space group C2/c with the lattice constants: a = 1529.4(7) pm, b = 1479.3(7) pm, c = 858.0(5) pm, β = 106.04(5)°. In the structure there are adamantanelike Ga4S10
8- anions, isosteric to the neutral P4S10 molecules. The Ba2+ ions are coordinated by 7 S atoms
A Convenient Preparation of Anhydrous Alkali Metal Thiocarboxylates
Authors: Kato Shinzi , Oguri Motohiro , Ishida Masaru
Published: February 2015

A series of alkali metal thiocarboxylates (1-5) were found to be readily obtained in high yields by the reaction of thiocarboxylic acids with metal hydrides (LiH, NaH, KH), and rubidium or caesium acetates, respectively. Their physical properties were disclosed
Verteilung und Valenz der Kationen in Spinellsystemen mit Eisen und Vanadium, IV. Rontgenographische und Mößbauer-spektroskopische Untersuchung des Spinellsystems FeV2O4-ZnV2O4 / Distribution and Valence of the Cations in Spinel Systems with Iron and Vanadium, IV X-Ray and Mössbauer Investigation of the Spinel System FeV2O4-ZnV2O4
Authors: Riedel Erwin , Anik Hümeyra
Published: February 2015

In the spinel system FeV2O4-ZnV2O4 pure Fe(II)-spinels could not be prepared. Mössbauer spectra show that the solid solution has the composition Fex
2+ Zn1-x:[Fey
3+ V2-y]O4, y depending on the partial pressure of oxygen during preparation. The reaction of 1/3 Fe + 1/3 Fe2O3 + V2O3 in a closed tube was also studied by X-ray and Mössbauer investigation
On the Walk Rearrangement of Cyclopentadienylphosphanes and Related Compounds - A Molecular Orbital Study
Authors: Schoeller Wolfgang W.
Published: February 2015

The walk rearrangement of cyclopentadienylphosphanes and related compounds is analyzed on the basis of a quantum chemical study. Although according to orbital symmetry considerations the reaction takes place with retention of configuration (at the migrating atom), inversion of configuration is also feasible. Low energy barriers for the walk reaction are expected if (a) radical stabilizing groups are attached to the cyclopentadienyl unit, (b) the fragment MR2 (migrating group) exerts strong radical stabilizing ability and (c) possesses energetically high lying frontier orbitals. The final goal, the device of a molecular structure which freezes in the transition state structure is discussed
Derivatives of NPCl2(NSOCl)2 and (NPCl2)2NSOCl, Part XXIII [1]. Reactivity in Aminolysis Reactions by NH3
Authors: Winter Herman , Grampel Johan C. van de
Published: February 2015

Reactions of the cyclic systems (NPCl2)2NSOX and NPCl2(NSOX)2 (X = F, Cl, Ph) with NH3 in diethyl ether or acetonitrile at low temperature provide convincing evidence that the P-bonded chlorine atoms are replaced by NH2 groups along a geminal pathway. No disruption of the S-F and S-Ph bonds occurs. Aminolysis of NPCl2(NSOCl)2 proceeds to NP(NH2)2(NSOCl)2, followed by decomposition, (NPCl2)2NSOCl can be transformed to NPClNH2NP(NH2)2NSOCl without cleavage of the ring skeleton
Ultraviolet Photoelectron Spectra of Square Planar Complexes of Nickel Triad Metals, I.He(I) and He(II) Spectra of [M{C6H3(CH2NMe2)2o,o′}X], (M = Ni, Pt; X = Cl, Br, I. M = Pd; X = Br)
Authors: Louwen Jaap N. , Grove David M. , Ubbels Henk J. C. , Stufkens Derk J. , Oskam Ad
Published: February 2015

UV photoelectron spectra of the title compounds are reported. Assignments based on He(I)/He(II) intensity differences, shift effects, and comparison with related molecules allow an assignment of the upper valence bands. Electronic differences between nickel and both platinum and palladium are reflected in the spectra, especially with respect to bands due to ionization of electrons from the metal.

Strong evidence is found for π interaction of the ligand phenyl system with metal orbitals
Flüssig-kristalline Verbindungen aus der Thiophenreihe 1. Flüssig-kristalline Thiophencarbonsäureester / Liquid Crystalline Compounds in the Thiophene Series 1. Liquid Crystalline Thiophene Carboxylic Esters
Authors: Koßmehl Gerhard , Budwill Detlev
Published: February 2015

Carboxylic esters have been prepared from 5-alkyl-2-thiophenecarboxylic acid and hydrochinone, biphenol, respectively cholesterol as well as one ester from 2,5-thiophene dicarboxylic acid and p-ethylphenol. Only the esters from biphenol respectively cholesterol have liquid crystalline phases
Über Arthropodenabwehrstoffe, LXV. Die Chemische Ökologie des Grundschwimmers Laccophilus minutus / On Arthropode Defensive Compounds, LXV. The Chemical Ecology of the Water Beetle Laccophilus minutus
Authors: Schildknecht H. , Weber B. , Dettner K.
Published: February 2015

According to a GC-MS analysis of methylated extracts the abdominal tips of the water beetle Laccophilus minutus (Dytiscidae) contain four β-hydroxyalkanoic acids. On the basis of MS and GC data another compound was assigned the structure of 6-octenoic acid.

The same β-hydroxyalkanoic acids, and in addition, traces of β-hydroxyheptanoic acids were identified in dissected pygidial defensive glands after trimethylsilylation. Methyl 3,4-dihydroxyphenylacetate was recognized as a further main component in the pygidial gland secretion from the mass spectrum of its TMSi ether.

The Laccophilinae occupy unique position among all the dytiscide subfamilies because they are the only water beetles which store β-hydroxyalkanoic acids in their pygidial glands. On the other hand the dytiscides appear to form a monophyletic group which is supported by the occurrence of methyl 3,4-dihydroxyphenylacetate. This class of compound is also commonly encountered in the other dytiscide subfamilies
A New Approach for the Synthesis of Some Pyridine and Pyridone Derivatives
Authors: Hishmat O. H. , Zohair M. M. Y. , Miky J. A. A.
Published: February 2015

Both visnaginone and khellinone react with malononitrile, ethyl cyanoacetate or cyanoacetamide in presence of ammonium acetate to give substituted furobenzopyrans or furobenzopyridones.

However, the reaction of visnaginone and khellinone with aldehydes, and malononitrile in presence of ammonium acetate leads to the formation of the corresponding 2-amino-4,6-disubstituted pyridine 3-carbonitriles. The latter compounds are also obtained by treating the respective chalcones with malononitrile and ammonium acetate.

3-Substituted 1,3-diketobutyrates form with malononitrile or with cyanoacetamide and ammonium acetate the 2-amino-4,6-disubstituted pyridine-3-carbonitriles or the 4,6-di-substituted cyanopyridones, respectively
Heterogene Katalyse, VII. Gasphasenhydrogenolyse von Polyhalogenverbindungen. Eine Möglichkeit zur Beseitigung chemischer Gift- und Abfallstoffe [1] / Heterogeneous Catalysis, VII. Gas Phase Hydrogenolysis of Polyhalogenated Compounds. Possible Decontamination of Poisonous Wastes [1]
Authors: Roth Wolfgang , Ragué Schleyer Paul von
Published: February 2015

Different catalysts were investigated with respect to their C-Cl-hydrogenolysis activity in perchloro compounds. C-Cl-hydrogenolysis to the parent hydrocarbon proceeds in the gas phase with a Pd/SiO2 catalyst in the presence of H2 at a temperature of 330 °C
Darstellung,11B-NMR- und Schwingungsspektren isomerenreiner Halogenohydrodecaborate XnB10H10- n
2-; X = Cl, Br, I; n = 1, 2 / Preparation, 11B NMR and Vibrational Spectra of Pure Isomeric Halohydrodecaborates XnB10H10- n
2-; X = Cl, Br, I; n = 1, 2
Authors: Preetz W. , Srebny H .-G . , Marsmann H. C.
Published: February 2015

Pure isomers of XnB10H10-n
2-; X = Cl, Br, I; n = 1, 2; are isolated by ion exchange chromatography on diethylaminoethylcellulose. Their structures are determined by11B and 11B {1H }NMR spectroscopy. There are characteristic chemical shifts due to apical and equatorial substituents, respectively. The highest field signals are explained by the antipodal effect. In contrast to theoretical predictions the experimental investigations show, that the successive electrophilic substitution preferably occurs on equatorial and not on apical B atoms. IR and Ram an spectra of the 2-XB10H9
2-species are very similar in the ν(BH) and in the B10- cage absorption region. In the far infrared there are two characteristic bands, shifting to lower frequencies in the series Cl, Br, I, which are therefore assigned to (B10) - X stretching and (B10) - X deformation modes.
Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen, XXIV. Elektronenmikroskopische Untersuchung der Hybridphasen Nb59O147F und Nb65O161F3 / Contributions to the Study of Inorganic Non-Stoichiometric Compounds, XXIV. Electronmicroscopical Investigation of the Hybrid Phases Nb59O147F and Nb65O161F3
Authors: Roß Ronald , Gruehn Reginald
Published: February 2015

The hybrid phases Nb59O147F and Nb65O161F3 were prepared at high temperature and investi­gated by high resolution transmission electron microscopy. Both phases have block structures. The sample of the phase Nb59O147F is very well ordered, whereas the phase Nb65O161F3 shows some defects. In a sample of Nb65O161F3 microdomains of a new 2:1 hybrid phase Nb96O238F4 were found. Structural differences of the systems Nb2O5/NbO2F and Nb2O5/WO3 are discussed.
Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe, IX [1]. Die Molekül- und Kristallstruktur von Tri-tert-butylcyclotriphosphanpentacarbonyl- chrom(O), [(t-BuP)3Cr(CO)5] / Structural Chemistry of Phosphorus-Containing Chains and Rings, IX [1]. The Molecular and Crystal Structure of Tri-tert-butylcydotriphosphane-pentacarbonyl-chromium (0), [(t-BuP)3Cr(CO)5]
Authors: Tebbe Karl-Friedrich , Fehér Magda
Published: February 2015

The structure of [(t-BuP)3Cr(CO)5], C17CrH27O5P3, has been determined by single crystal X-ray techniques, solved by ‘direct methods', and refined to R = 0.048, wR = 0.050 for 3657 reflections by blocked least squares. The compound crystallizes in the space group P 21/c with a = 1664.9 pm, b = 916.5 pm , c = 3089.8 pm, β= 91.45° and Z = 8 formula units.

The structure consists of two crystallographically independent but structurally nearly identical mononuclear [(t-BuP)3Cr(CO)5] complexes with the three-membered ring (t-BuP)3 as an unidentate σ-donor ligand. Compared to the free molecule (t-BuP)3 the cyclophosphane ligand is slightly distorted on account of its coordination to the Cr(CO)5-group.
Sandwich-Komplexe des Palladiums und Platins [1] / Sandwich Complexes of Palladium and Platinum [1]
Authors: Wadepohl Hubert , Siebert Walter
Published: February 2015

1,3,4,5-Tetraethyl-2-methyl-1,3-diborolene (1) reacts with MX2 (M = Pd, Pt) and Na(C5H5) to give orange-red cyclopentadienyl(1,3-diborolenyl)palladium 3 and the yellow platinum complex 4, respectively. Bis(1,3,4,5-tetraethyl-2-methyl-1,3-diborolenyl)platinum (5) is obtained in low yield from 1, Na(HBEt3) and PtCl2 or from 1 and [(C2H4)PtCl2]2. 1H, 11B, and 13C NMR data of 3, 4, and 5 are in agreement with a sandwich structure. The 16e complex 5 is reduced by potassium to its mono- and dianion.
Reaktion der Alkoxo-oxovanadium(V)-chloride mit Lithium-alkyl-trimethylsilylamid / Reaction of Alkoxo Oxovanadium(V) Chlorides with Lithium Alkyl Trimethylsilylamide
Authors: Preuss Fritz , Fuchslocher Edith , Towae Willi
Published: February 2015

The aminovanadium(V) compounds VO(OR)2[NR'(SiMe3)] and VO(OR)[NR'(SiMe3)]2 have been prepared by reaction of LiNR'(SiMe3) with VO(OR)2Cl and VO(OR)Cl2, respectively; their spectroscopical data (1H NMR, IR, MS) are reported. All compounds are monomeric in solution. In some cases 1.3 migration of SiMe3 groups from nitrogen to oxygen is observed on heating. Kinetic measurements indicate the rearrangement reaction to be irreversible and intramolecular. The reaction of VO(OR)Cl2 with HNR'(SiMe3) leads to iminovanadium(V) compounds such as R'N = V(OSiMe3)3, R'N = V(OSiMe3)2(OR) and R'N = V(OR)2Cl.
1H-DNMR-Untersuchungen zur inter- und intramolekularen Ligandenmobilität im System Co(II)/[18]Krone-6 / 1H DNMR Studies on the Inter- and Intramolecular Ligand Mobility in the System Co(II)/[18]crown-6
Authors: Dickert Franz L. , Gumbrecht Walter
Published: February 2015

The crown ether exchange could be studied in non-coordinating solvents by using the hy­drophobic complex [Co([18]crown-6)] + + . Appreciable outer-sphere association between complex and ligand (K°(50 °C) = 12 ± 0.5 M-1) occurs. This changes the second order rate law to first order (kmono(50 °C) = 7900 ± 500 s_1) with increasing ligand concentration. In the complex mer-[Co([18]crown-6)(CH3OH)3]+ + the stereochemical rearrangement of the uncoordinated part of the crown ether follows an intramolecular pathway via the complex [Co([18]crown-6)]++ as an intermediate product.
Bis-Phosphino-Derivate des Cyclooctatetraens / Bis-Phosphino-Derivatives of Cyclooctatetraene
Authors: Benn Reinhard , Mynott Richard , Richter Wolf Jurgen
Published: February 2015

Magnesium-COT reacts with diorganochlorophosphines to yield 1,2-diphosphino-substituted cyclooctatrienes. While the methyl compound leads to ring-concentration, larger substituents at phosphorus give rise to 1,8-diphosphino-octatetraenes (E, Z, Z, E) via retro-electrocyclization. The compounds are fully characterized by NMR.
Synthesis of 1-(2,4-DinitrophenyI)-3-methyl-4-substituted HeterocycIes-2-pyrazolin-5-one
Authors: Youssef Mohamed Salah Kamel
Published: February 2015

4-Bromo-1-(2,4-dinitrophenyl)-3-methyl-2-pyrazolin-5-one was reacted with the sodium salt of some reactive methylene compounds and then condensed with hydrazine hydrate, phenyl hydrazine, hydroxylamine hydrochloride, urea and thiourea to obtain the 4-substituted heterocy- cles-5-pyrazolones.
Eine RingÖffnungsreaktion von Hydroperoxiden cyclischer Ether / A Ring Opening Reaction of Hydroperoxides of Cyclic Ethers
Authors: Ockels W. , Stein J. , Budzikiewicz H.
Published: February 2015

2-Hydroperoxides of cyclic esters react with pyridine-2,6-di(monothiocarboxylic acid) in form of its iron complex by attack of the thiocarboxylate anion at C-3, opening of the ether ring and formation of a thioester carrying a acyloxy group in the alcohol portion. A typical example is the formation of pyridine-2,6-di(monothiocarboxylic acid)-di-S-(3-formoxypropyl)ester from tetra- hydrofuran-2-hydroperoxide.
Synthese von 1-Aryl-4-carboxymethyl-2-azetidinonen / Synthesis of 1-Aryl-4-carboxymethyl-2-azetidinones
Authors: Ongania Karl-Hans , Pawlowski Renata
Published: February 2015

The photochemically induced rearrangement of the 4-diazoacetyl-2-azetidinones 2a-d in wa- ter/acetonitrile leads exclusively to the title compounds 3 a-d provided that certain reaction conditions are fulfilled. This is in contrast to the thermal, silveroxide catalysed Wolff-rearrange- ment of 2a in alcohols which always gives a mixture of 4, 5 and 6. The mechanism of the 1,4-ringopening of 2a to 5 and 6 is discussed.
Prevention of Tryptophan Oxidation During Iodination of Tyrosyl Residues in Peptides
Authors: Mourier G. , Moroder L. , Previero A.
Published: February 2015

Studies on model systems clearly revealed oxidative degradation of tryptophan under the usual conditions of iodination of tyrosine residues in peptides, whereby the rate of former reaction was found to be faster than the iodination itself. Nin-formylation of tryptophan brings about an efficient indole protection against this oxidative degradation.
Die Kristallstruktur von PPh3Me[NbOCl4(CH3CN)] / The Crystal Structure of PPh3Me[NbOCl4(CH3CN)]
Authors: Hiller W. , Strähle J. , Prinz H. , Dehnicke K.
Published: February 2015

The X-ray structure of PPh3Me[NbOCl4(CH3CN)] at 210 K was solved (space group P1̄, two formula units per unit cell, a = 1173.5(5), b = 1130.1(4), c = 946.8(3) pm, α = 97.70(4), β = 93.57(3), γ = 78.62(3)°, 3688 inde­pendent reflexions, R = 0.025).

The material consists of cations [P(C6H5)3CH3]⊕ and anions [NbOCl4(CH3CN)]⊖. The nitrogen atom of the acetonitrile solvate molecule is coordinated to the niobium centre in the trans-position to the oxo ligand; the NbO bond length of 169 pm corresponds to a double bond.
Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, XXXVI [1]. Neuartige Phosphanliganden mit asymmetrischen Phosphor-oder Kohlenstoffatomen / Preparation and Properties of, and Reactions with, Metal-Containing Heterocycles, XXXVI [1]. Novel Phosphane Ligands Containing Asymmetric Phosphorus or Carbon Atoms
Authors: Lindner Ekkehard , Küster Ernst Ulrich
Published: February 2015

The functionalized ligands (H3C)PhP-(CH2)n-Cl (1, 2) [n = 2 (1), 3 (2)] and Ph2P-CH2-OMen (3) with asymmetric phosphorus or carbon atoms which are suitable for the synthesis of diastereomeric metallacycles, are obtained in THF/ether by reaction of (H3C)PhPLi and Ph2PLi with Cl - (CH2)n-Cl and Cl-CH2-OMen, respec­tively. The structures of 1-3 are discussed on the basis of their mass and NMR spectra.
The Crystal Structure of Sodium Nickel Arsenate, NaNiAsO4
Authors: Range Klaus-Jürgen , Meister Helmut
Published: February 2015

The unit cell of NaNiAsO4 is rhombohedral, space group R 3, with a = 4.955(5) Å, c = 26.47(3) Å and Z - 6. The crystal structure com­prises three-layer units consisting of one “octahe­dral" layer, built up from Ni06-octahedra, and two “tetrahedral" layers, built up from AsO4-tetrahe- dra. Sodium ions are situated between these layers, having a distorted (4+3) coordination.
Bildung von Diammoniumdihydrogendiphosphat durch spontane Kondensation der Amidophosphorsaure in waBriger Losung / Formation of Diphosphate from Amidophosphoric Acid in Aqueous Solution
Authors: Seel Fritz , Klein Norbert
Published: February 2015

A nearly saturated solution of amidophosphoric acid in water hydrolyses to yield diammonium diphosphate. This reaction provides a diphosphate synthesis in water starting with a solution of N- methylcarbamoylphosphate which is readily ob­tained through the action of methylisocyanate upon the aqueous solution of a hydrogenphosphate.
Metallomethane, XI [1]. Einfache Darstellung von Tetrakis(halogenoquecksilber)methanen C(HgX)4 (X = F, Cl, Br und I) / Metallomethanes, XI [1]. Simple Preparation of Tetrakis(halomercuri)methanes C(HgX)4 (X = F, Cl, Br and I)
Authors: Breitinger Dietrich K. , Neufert Ronald , Nowak Manfred
Published: February 2015

A simple procedure for the preparation of tetra- kis(halomercuri)methanes C(HgX)4 (X = F, Cl, Br and I) from Hofmann’s base (“oxymercarbide”) and aqueous hydrohalic acids is described. Under the reaction conditions used, degradation of the CHg4 moieties present in Hofmann’s base also occurs, in­creasing in the series HF ≈ HC1 < HBr < HI.
Neue Synthese von 6-Formyl-trans- 5.6-methanohexansäuremethylester / Novel Synthesis of Methyl 6 -Formyl-trans- 5.6-methanohexanoate
Authors: Spur Bernd , Crea Attilio , Peters Wilfried
Published: February 2015

Methyl 7-oxo-5-trans-heptenoate reacts with diazomethane in the presence of Pd(CH3COO)2 in high yield to the cyclopropane aldehyde 1, an im­portant intermediate in the 5,6-methanoleukotriene synthesis.
The Isolation and Structure of “ Papilicine” — a New Alkaloid from Buxus papilosa
Authors: Atta-ur-Rahman  , Nisa Mehrun , Zamir Talat
Published: February 2015

A new alkaloid, “papilicine”, has been isolated from the leaves of Buxus papilosa to which structure (1) has been assigned on the basis of spectroscopic studies.
Oxidative Addition Reactions of P(CN)3, P(NCO)3 and P(NCS)3 to (η5-C5Me5)Co(CO)2
Authors: Delgado S. , Macazaga J. , Masaguer J. R.
Published: February 2015

The phosphorus pseudohalogens P(CN)3, P(NCO)3 and P(NCS)3 react with (η5-C5Me5)Co(CO)2 to give the complexes (η5-C5Me5)Co(CO)XPX2 (X = CN, NCO, NCS). All the compounds are characterized by elemental analysis, IR. electronic and 1H NMR spectra
Synthese und Strukturuntersuchungen von Iodocupraten(I), III. Iodocuprate(I) mit isolierten Ketten 1
∞[Cu2I3]– bzw. 1
∞[Cu3I4]– [1] / Synthese und Strukturuntersuchungen von Iodocupraten(I), III. Iodocuprate(I) mit isolierten Ketten 1
∞[Cu2I3]– bzw. 1
∞[Cu3I4]–
Authors: Hartl Hans , Mahdjour-Hassan-Abadi Farbod
Published: February 2015

N-Methylpyridinium-triiododicuprate(I), C6H8NCu2I3, methyltriphenylphosphonium-tetraiodotricuprate( I), (C6H5)3CH3PCu3I4 and tetrapropylammonium-tetraiodotricuprate(I), (C3H7)4NCu3I4 were obtained by reacting Cu with I2 and C6H8NI, (C6H5)3CH3PI or (C3H7)4NI in acetone. The crystal structures of these compounds are built up by the cations and isolated chains of edge or face sharing Cul4-tetrahedra: [C6H8N ]+
1
∞[(CuI2/2I2/4)-, [(C6H5)3CH3P]+
1
∞[(CuI1/2I2/3I1/4)2 (CuI2/3I2/4)]- and [(C3H7)4N]+
1
∞[(CuI3/3I1/2)2 (CuI3/3)]-. There are very short Cu···Cu distances of 246.1(5) and 250.3(5) pm in (C3H7)4NCu3I4 produced by face sharing of Cul4-tetrahedra
Impedance of an Oxygen Reducing Gas-Diffusion Electrode
Authors: Wabner Dietrich , Holze Rudolf , Schmittinger Peter
Published: February 2015

The impedance of teflon bonded electrodes was measured in the frequency domain. These electrodes based on activated carbon as electrocatalyst were developed for fuel cell applications. When feeding the electrode with air or oxygen the impedance spectra could be explained by two Nernst diffusion processes and a small charge transfer process.

Two methods for separating the measured impedance into partial impedances related to different steps of the electrode reaction are presented. A least square fit procedure is described which has been applied successfully to the impedance analysis of porous electrodes
Ringöffnungsreaktionen eines Benzodithiazolium-chlonds und die Röntgenstrukturanalyse von 3.3' .5.5'-Tetrakis-tert-butyl- 2.2'-bissulfinyIamino-1.1'-diphenyl-disulfid / Ring Cleavage of a Benzodithiazolium-chloride and the X-Ray Structure Analysis of 3,3' ,5,5 '-Tetrakis-terr-butyl-2,2'-bissulfinylam ino-1, 1'-diphenyl-disulfide
Authors: Roesky Herbert W. , Weber Karl-Ludwig , Noltemeyer Mathias , Sheldrick George M.
Published: February 2015

4,6-Di-tert-butyl-1,2,3-benzodithiazolium-chloride (1) reacts with Ph3P=NSi(CH3)3 (2) or Na[N(Si(CH3)3)2] (3) in the presence of oxygen to yield 3,3',5,5'-tetrakis-tert-butyl-2,2'-bissulfinyl- amino-1,1'-diphenyl-disulfide (4), which was characterized by X-ray structure determination. Crystals of 4 are triclinic, space group P1, with a = 1043.6(4), b = 1088.8(7), c - 1451.5(7) pm, a - 76.69(5), β = 80.67(3) and γ = 77.91(4)°
Diazadiene als Steuerliganden in der Homogenen Katalyse, VIII [1] Katalytische Trimerisierung substituierter Acetylencarbonsäureester und Isolierung eines Acetylendicarbonsäureester-Diazadien-Nickel(0)-Addukts / Diazadienes as Controlling Ligands in Homogeneous Catalysis, VIII [1] Catalytic Trimerization of Substituted Acetylene Carbonic Acid Esters and Isolation of an Acetylene Dicarbonic Acid Ester Diazadiene Nickel(0) Adduct
Authors: Diercks Rainer , tom Dieck Heindirk
Published: February 2015

Nickel(0) complexes of diazadienes (dad = RN = CR' - CR ' = NR ) catalyse the trimerization of esters of 2-butynoic acid, phenylpropynoic acid and butynedioic acid to give hexasubstituted benzenes with the unsymmetrical esters 2 as the main products. A primary adduct 7 of acetylene dicarboxylic acid dimethyl ester of the type (dad)Ni(alkyne) could be isolated and characterized by 1H NMR, IR and UV spectroscopy. According to their characteristic CT absorption. 7 and its analogues are shown to persist during catalysis as an active species
Darstellung und Charakterisierung von Berlinerblau-Analoga des Typs Ti[MB(CN)6] / Preparation and Characterization of Prussian Blue Analogs of the Type Ti[MB(CN)6]
Authors: Inoue Hidenari , Fluck Ekkehard
Published: February 2015

Three compounds of the type Ti[MB(CN)6] (MB = Co, Rh, and Ir) have been synthesized and characterized by means of their X-ray diffraction powder patterns, magnetic measurements, infrared, electronic, and X-ray photoelectron spectra. All compounds crystallize in the facecentered cubic system and form a three-dimensional framework of two octahedral coordination units MBC6 and TiN6. Upon the formation of Ti[MB(CN)6] from the corresponding potassium salt, the π back-donation in the [MB(CN)6]3- moiety is enhanced by the bridge formation through the cyanide ligand
Structure of the Linear-Chain Mixed Valence Compound Bis(l,3-diaminopropane)platinum(II)bis(l,3-diaminopropane)- diiodoplatinum(IV)tetraperchlorate
Authors: Cannas Mario , Marongiu Giaime , Keller Heimo J. , Müller Barbara , Martin Reinhold
Published: February 2015

The title compound C12H49Cl4I2N8O 16Pt2, Mr 1314.1, is monoclinic P 21 (from structural analysis), a = 8.74(1), b = 11.36(1), c = 8.63(1), β = 107.6(5), V = 817 Å3, Z = 1, Dm (flotation) = 2.65 g cm-3, Dc = 2.66 g cm-3, MoKɑ λ = 0.71069, μ = 110.7 cm-1, R = 0.063 for 1068 observed reflections. Rotation photographs show diffuse patterns corresponding to odd values of k together with weak Bragg reflections. Refinement of diffractometer data was carried out in space groups Pm, P21/m and P21; both refinement in Pm and P21 give satisfactory agreement and lead to very similar crystal structures
Die Kristallstruktur des elpasolith-verwandten Cyanokomplexes [N(CH3)4]2NaFe(CN)6 • H2O / The Crystal Structure of the Elpasolite-Related Cyano Complex [N(CH3)4]2NaFe(CN)6 • H2O
Authors: Witzei M. , Babel D.
Published: February 2015

The compound [N(CH3)4]2NaFe(CN)6 • H2O crystallizes in the orthorhombic space group Pnma, Z = 4, a - 1863.9(2), b = 861.7(1), c - 1317.2(2) pm. The X-ray single crystal structure determination (2515 reflections, R - 0.04) revealed an elpasolite-related framework of slightly deformed Fe(CN)6
3- octahedra, the mean distances in which are Fe-C = 194.0 and C-N = 113.9 pm. The strongly distorted octahedral N6 cavities formed by six Fe(CN)6
3- units are occupied by monohydrated sodium ions, exhibiting a very short distance Na-O = 221.8(3) pm. By approach to one of the octahedral faces within their N6 environment the sodium ions obtain a distorted tetrahedral NaON3 coordination, Na-N = 2 x 238.0(3) and 241.3(3) pm. One of the compound’s two tetramethylammonium ions, which are centered at mirror planes, is orientationally disordered. The reason for this is discussed
Methylperoxyl Radicals: A Study of the γ-Radiolysis of Methane in Oxygenated Aqueous Solutions
Authors: Schuchmann Heinz-Peter , Sonntag Clemens von
Published: February 2015

A product study has been made of the γ-radiolysis of aqueous methane solutions that also contained nitrous oxide and oxygen. Formaldehyde (G = 2.8), hydrogen peroxide (G = 2.1), methanol (G = 1.5), methylhydroperoxide (G = 0.8), formic acid (G = 0.3), and dimethylperoxide (G = 0.1) were found. In alkaline solutions (pH 8, 10-3 M phosphate buffer), the formaldehyde yield rises to G = 3.2, while the formic acid yield falls to almost zero (G = 0.05). The initial precursor of the carbon-containing products is the methylperoxyl radical. The methylperoxyl radicals decay through a short-lived tetroxide along various pathways. The most prominent one leads to formaldehyde, methanol and oxygen. Methoxyl radicals (and oxygen) are also formed and, after rearrangement into hydroxymethyl radicals and their conversion into hydroxymethylperoxyl radicals, eventually yield formic acid and probably further formaldehyde. A route to formaldehyd and hydrogen peroxide is also envisaged. Methylhydroperoxide is formed in the reaction of methylperoxyl radicals with HO2 /O2·̄ radicals (from radiolytic H atoms and the unimolecular decay of the hydroxymethylperoxyl radical)
Metallkomplexe mit Tetrapyrrol-Liganden, XXXIII [1] Darstellung von Azidochrom(III)-, Azidomangan(III)- und Azidoeisen(III)-Porphyrinen und deren Photolyse zu terminalen oder verbrückten Nitridometallporphyrinen / Metal Complexes with Tetrapyrrole Ligands XXXIII [1] Preparation of Azidochromium(III)-, Azidomanganese(III)-, and Azidoiron(III) Porphyrins and their Photolysis to Terminal or Bridged Nitridometal Porphyrins
Authors: Buchler Johann Walter , Dreher Christine
Published: February 2015

Azidometal(III) porphyrins, e.g. M(TTP)N3 1 Aa-1 Ca (M = Cr, Mn, Fe), are transformed into nitrido complexes on irradiation with ultraviolet light. Thus, CrIII or MnIII complexes, e.g. Cr(TTP)N3 or Mn(TTP)N3, yield Crv and Mnv complexes with terminal nitride ligands, e.g. Cr(TTP)N (1Ab) or Mn(TTP)N (1Bb) with concomitant liberation of 1 mol of N2. However, the FeIII complex Fe(TTP)N3 produces the mixed-valence ,μ-nitrido-bis[iron(III,IV)] complex, [Fe(TTP)]2N (1Cg) and about 1.2 mol of N2 per mol of Fe. The azidometal(III) porphyrins are prepared from the corresponding hydroxo- or μ-oxo-metal(III) porphyrins and hydrazoic acid in benzene
Fluorescence Properties of Hydroxy- and Methoxyflavones and the Effect of Shift Reagents
Authors: Wolfbeis Otto S. , Begum Monowara , Geiger Hans
Published: February 2015

The fluorescence spectra of 42 hydroxy- and methoxyflavones in methanol solution have been investigated. The following findings are considered to be useful in structure elucidation and identification of flavonoids: (a) The maxima of the absorption and fluorescence bands give, in most cases, a unique combination; (b) flavones exhibit exceptionally large Stokes’ shifts (6,800 to 10,000 cm-1); (c) most flavones fluoresce blue, but flavonols fluoresce yellow or green; the fluorescence of flavonols consists frequently of two bands; (d) fluorescence is zero or very weak for 5-hydroxyflavones; (e) 5-hydroxyflavones become increasingly fluorescent with in increasing number of oxygen functions being present in the molecule; a 3-hydroxy group has a particular beneficial effect; (f) hydroxyflavones fluoresce less intense than the corresponding m ethoxyflavones; (g) fluorescence intensity is distinctly higher in polar protic than in apolar solvents.

The effects of three groups of shift reagents on the spectra has also been investigated. The first group involves water, 10% and 50% sulphuric acid. The second group consists of basic reagents (sodium acetate, sodium hydrogen carbonate and sodium carbonate), and the third group of com plexing reagents such as aluminum trichloride, borax and magnesium sulphate. The following generalisations may be made: (a) Water causes a bathochromic shift in emission with 7-hydroxyflavones, but a hypsochromic shift with flavonols; (b) 50% sulphuric acid is able to protonate (and thus to longware-shift the em ission maximum) of all flavones except for the 3-, 5-, and 8-hydroxy isomers; (c) sodium acetate and hydrogen carbonate cause characteristic shifts with 7-hydroxyflavones and, occasionally, with 4 '-hydroxyflavones lacking a 7-hydroxy group; (d) aluminum trichloride produces a longware shift and an enorm ous increae in fluorescence intensity with flavonols; (e) borax can be used to detect sensitively the presence o f a 3 ',4 '-dihydroxy group
The Absorption and Fluorescence of Isoflavones and the Effect of Shift Reagents
Authors: Wolfbeis Otto S. , Fiirlinger Eva , Jha Hem Chandra , Zilliken Fritz
Published: February 2015

The absorption and fluorescence maxima of 20 isoflavones have been determined in methanol solution and the effect of addition of water, 50% sulfuric acid, aluminium trichloride, borax, sodium acetate, ammonia and sodium hydroxide has been studied. The following findings may be useful in the structure elucidation of naturally occurring isoflavones: (a) 5-Hydroxyisoflavones have band I absorption maxima around 335 nm. 6-hydroxyisoflavones between 310 and 330 nm, and others below 310 nm. (b) Addition of water produces practically no shift in the absorption spectra, but - unlike other hydroxyisoflavones - can give distinctly longwave shifted new fluorescence bands with 7-hydroxyisoflavones. (c) Addition of sodium acetate gives rise to anion absorption of 7-hydroxyisoflavones and to partial anion absorption of 6-hydroxyisoflavones; the spectral maxima of 5-hydroxyisoflavones remain practically unchanged, (d) Ammonia gives rise to anion absorption of both 6- and 7-hydroxyisoflavones, but not of the 5-hydroxy isomers, (e) Sodium borate is a useful reagent to identify 6,7-dihydroxyisoflavones by virtue of its ability to form a chelate complex with an absorption maximum that is different from the anion absorption, (f) Aluminium trichloride forms complexes with both 5-hydroxy- and 6,7-dihydroxyisoflavones with distinct absorption maxima, (g) 5,7-D ihydroxyisoflavones may be recognized by addition of ammonia, which does not result in a longwave shift, but rather in an intensification of the longwave absorption band, (h) 6-H ydroxyisoflavones can be differentiated from the 7-hydroxy isomers by their longwave shifts (4 0-60 nm) following addition of ammonia. The respective shifts of the 7-hydroxy isomers are smaller, (i) 5-H ydroxyisoflavones are practically non-fluorescent. while others have fairly strong fluorescences, (j) The absorption and fluorescence maxima of isoflavones give unique combinations which may be useful in their identification, (k) Addition of aluminium chloride makes the non-fluorescent 5-hydroxyisoflavones fluorescent. (1) As in the case of absorption, 6,7-dihydroxyisoflavones form complexes with borate possessing fluorescence bands with maxima different from those of the anion bands
Dimere Naphthochinone, X* Ein neuartiger Syntheseweg zu Desapogossypolon-tetraethylether / Dimeric Naphthoquinones, X* A Convenient Synthesis of Desapogossypolone Tetraethyl Ether
Authors: Laatsch Hartmut
Published: February 2015

Desapogossypolone tetraethyl (2b), a degradation product of gossypol (1), was obtained in a simple way by oxidative coupling of 6,7-diethoxy-4-methoxy-1-naphthol (7c) and C-methylation with diazomethane
Biosynthesis of Riboflavin Preparation of Phosphorylated Pyrimidine Intermediates
Authors: Bacher Adelbert
Published: February 2015

2-Amino-5-nitro-6-(1'-D -ribityl)amino-4(3H)-pyrim idinone (6a) was converted to the dimethoxytrityl derivative, which was subsequently acetylated. The trityl residue was then removed, and the com pound was phosphorylated by the cyanoethyl method. Removal of the protecting groups yielded 2-am ino-5-nitro-6-(1'-D -ribityl) aminopyrimidinone 5'-phosphate (11a). Catalytic hydrogenation yielded the labile 2,5-diam ino-6-(T -D -ribityl) amino-4(3H )-pyrimidinone 5'-phosphate (3a) which is the substrate for a deaminase from yeast. 5-Amino-6-(1'-D -ribityl) amino- 2,4(1 H ,3H )-pyrim idinedione 5'-phosphate (3b) was prepared by an analogous sequence of reactions. It was further converted to 6,7-dimethyl-8-(1'-D -ribityl) lumazine 5'-phosphate (12b). The phosphoric acid esters prepared by the present procedures contained about 20% of an undesired isomer as a consequence of insufficient selectivity of the tritylation reaction