bluuebunny/crossref_metadata_2025_split huggingface dataset:
2,6‐Dicyano‐1,5‐dimethyl‐4,8‐diphenylsemibullvalene. — Synthesis, Structure and the Reactions with Triplet Oxygen
Authors: Quast Helmut , Herkert Thomas , Witzel Alexander , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg 
Published: July 2007

AbstractAddition of trimethylsilyl cyanide to the diphenylbicyclo[3.3.0]octanedione 8c is catalyzed by the potassium cyanide/18‐crown‐6 complex and produces a mixture of the diastereomeric bis[O‐(trimethylsilyl)cyanohydrins] endo‐ and exo‐10c (3:2). The hydrogen fluoride—pyridine complex in phosphorus oxychloride as solvent and, subsequently, an excess of pyridine convert the mixture of diastereomers 10c into the unsaturated y,y′‐diphenyldinitrile 11. This is converted into the red semibullvalene 4 in a single step by treatment with hexachloroethane and concentrated aqueous sodium hydroxide in the presence of tetrabutylammonium hydroxide as phase‐transfer catalyst — Above 30°C, 4 isomerizes in solution to a mixture of the cyclooctatetraenes 12 and 13. While the red crystals of 4 are stable in the atmosphere, in the dark affording the endoperoxide 16 and the yellow 2H‐pyran derivative 17 (7:1) which result from parallel reactions. Only at temperatures as high s 110°C, 16 slowly rearranges to 17 which reacts further to yield well‐defined but still unknown products. The simultaneous formation of 16 and 17 at low temperatures is interpreted in terms of endo and exo attack, respectively, of triplet oxygen at the benzylic carbon atoms of the semibullvalene 4 or the isomeric bicyclic diradical 21. — The structures of the new compounds are based on spectroscopic evidence and X‐ray diffraction analyses of 4, endo‐10c, 11, 16, and 17. The semibullvalene 4 exists as a pair of rapidly rearranging degenerate valence tautomers in solution and in the crystal as well. In the solid state, 4 exhibits apparent C2 symmetry and equal atomic distances C2–C8 and C4–C6 (201.9 pm). Because true degeneracy is highly unlikely in the crystal, the equal distribution of two non‐equivalent valence tautomers at room termperature results from a fortuitous cancelling of the ΔH° and TΔS° terms governing the equilibrium. — The red colour of 4 in the crystal and in solution is due to a maximum at 444 nm which disappears on cooling. Thus, 4 not only belongs to the family of thermochromic semibullvalenes and barbaralanes devoid of a long wavelength chromophor like 1, 6 and 14, but also shows the most intensive maximum at the longest wavelength observed so far.
Photoenolization of 4‐Naphthoyl[2.2]paracyclophanes
Authors: Hopf Henning , Laue Thomas , Zander Maximilian 
Published: July 2007

AbstractWhen ethanolic solutions of 4‐(1‐naphthoyl)[2.2]paracyclophane (3) and 4‐(2‐naphthoyl)[2.2]paracyclophane (4) are subjected to UV irradiation at low temperature, 1,5‐hydrogen migration of the 2‐H bridge proton to the carbonyl group takes place, leading to the enol of type 2. In the context of mechanistic considerations the triplet spectroscopic properties of 3 and 4 are discussed.
Thermolabile Hydrocarbons, 33. Thermochemistry and Thermal Decomposition of 9,9′‐Bifluorenyl and 9,9′‐Dimethyl‐9,9′‐bifluorenyl – The Stabilization Energy of 9‐Fluorenyl Radicals
Authors: Rakus Klaus , Verevkin Sergej P. , Schätzer Jürgen , Beckhaus Hans‐Dieter , Rüchardt Christoph 
Published: July 2007

AbstractFrom thermochemical measurements the heats of formation ΔH0f(g) forfluorene (1), 9‐methylfluorene (2), 9,9′‐bifluorenyl (5), and 9,9′‐dimethyl‐9,9′‐bifluorenyl (6) were determined. The homolytic cleavage of the dimers 5 and 6 to 9‐fluorenyl (3) and 9‐methyl‐9‐fluorenyl radicals (4), respectively, was studied in mesitylene with thiophenol as trapping agent and found to follow first‐order kinetics. The activation parameters ΔH≠(5) = 212.6 (±2.1) kJ mol−1, ΔS≠(5) = 70.3 (±4.2) J mol−1 K−1 ΔH≠(6) = 164.9 (±0.7) kJ mol−1, and ΔS≠(6) = 88.2 (±1.9) J mol−1 K−1 were obtained. For 3 and 4 the radical stabilization energies RSE(3) = 67 (±7) kJ mol−1 (relative to isopropyl) and RSE(4) = 64 (±8) kJ mol−1 (relative to tert‐butyl) were determined by a comparison with the activation parameters of the thermolysis of alkanes possessing the same strain enthalpy. The heats of formation for 3 and 4 and the C–H bond dissociation energies for the C–H bond in the 9–position of 1 and 2 were determined to be ΔH0f(g,3) = 300 kJ mol−1, Δ0f(g,4) = 268 kJ mol−1, BDECH(1) = 343 and BDECH(2) = 338 kJ mol−1 (estimated errors correspond to those of the RSE values). A good correlation between the heats of vaporization of 37 aromatic hydrocarbons and their calculated solvent‐accessible surfaces was demonstrated. Hence, a new method to estimate heats of vaporization was established.
Characterization of Neutral and Ionic Sulfur—Nitrogen Cluster Molecules NS2 and NS3 in the Gas Phase
Authors: Iraqi Muhammad , Goldberg Norman , Schwarz Helmut 
Published: July 2007

AbstractCollision experiments on NS−x (x = 2, 3) clusters are reported. Evidence is presented for the gas‐phase existence of the corresponding NS.x and NS+x species. For x = 3, the mass spectra are very much in keeping with a connectivity SS‐NS (5) for all three charge states. For x = 2, the experimental data favor the presence of NSS (2); however, the cyclic C2v‐symmetric form 3 cannot be ruled out.
Konstitution und Farbe von Alizarin‐ und Purpurin‐Farblacken
Authors: Wunderlich Christian‐Heinrich , Bergerhoff Günter 
Published: July 2007

Constitution and Colour of Alizarin and Purpurin DyesThe colour of madder dyes used as pigment in antiquity and in the last centuries is produced mainly by metal complexes of alizarin (1) and purpurin (2). Single crystals of aluminium calcium alizarinate and purpurinate are obtained by two‐phase crystallization. X‐ray structure determinations show tetranuclear complex molecules with four alizarins which are different from formerly proposed structures. Solutions of 17 metal complexes of alizarin in DMF/Water exhibit UV‐Vis spectra the maxima of absorption of which strongly depend on the electronegativity of the metals. A classical explanation for this is given.
Radikalische Cyclisierung von Dienen, IX. Über die Stereoselektivität der radikalischen 4‐exo‐trig‐Cyclisierung von optisch aktiven (2E)‐6‐Oxohex‐2‐ensäureestern mit Samarium(II)‐iodid
Authors: Weinges Klaus , Schmidbauer Stefan B. , Schick Hartmut 
Published: July 2007

Radical‐Type Cyclization of Dienes, IX. ‐ On the Stereoselectivity of the Radical 4‐exo‐trig‐Cyclization of Optically Active Ethyl (2E)‐6‐Oxohex‐2‐enoates with Samarium(II) IodideEthyl (5R, 2E)‐5‐(benzyloxy)‐4,4‐dimethyl‐6‐oxohex‐2‐enoate (9) was prepared from (R)‐(‐)‐pantolactone (3) by a series of straightforward reactions. The reaction of 9 with samarium(II) iodide produces enantiomerically pure ethyl (1S,3R,4R)‐(‐)‐[3‐(benzyloxy)‐4‐hydroxy‐2,2‐dimethylcyclo‐butyl]acetate (10) in 60% yield. The absolute configuration at C‐1 and C‐3 was confirmed by the conversion of 10 to the crystalline 15a, whose absolute configuration is known from its synthesis from (1S,5S)‐( + )‐α‐pinene (12). The configuration of the hydroxy group at C‐4 in 10 was determined from NOE studies on the epimiric 17. The radical 4‐exo‐trig‐cyclization of optically active (2E)‐6‐oxohex‐2‐enoates with samarium(II) iodide opens a new pathway to enantiomerically pure cyclobutanol and cyclobutanone derivatives, which are of interest as building blocks in natural products synthesis.
Kohlenwasserstoffverbrückte Komplexe, XXX. Nucleophile Addition von Carbonylmetallaten an kationische Vinyl‐, Dien‐, Dienyl‐ und Trien‐Komplexe von Eisen, Ruthenium und Cobalt: Zwei‐, drei‐, vier‐ und fünfkernige Komplexe mit σ,σ‐ und σ,π‐Kohlenwasserstoffbrücken
Authors: Hüffer Stephan , Wieser Michael , Polborn Kurt , Sünkel Karlheinz , Beck Wolfgang 
Published: July 2007

Hydrocarbon‐Bridged Complexes, XXX. — Nucleophilic Addition of Carbonylmetallates to Cationic Vinyl, Diene, Dienyl and Triene Complexes of Iron, Ruthenium and Cobalt: Di‐, Tri‐, Tetra‐ and Pentametallic Complexes with σ,σ‐ and σ,π‐Hydrocarbon BridgesHerrn Professor Ekkehard Lindner zum 60. Geburtstag gewidmet.
The reactions of [Re(CO)5]−, [Ru(CO)2Cp]−, and [Os(CO)4]2− with [Cp2(OC)2Fe2(μ‐CO)(μ‐η1:η2‐CH=CH2)]+, [Cp*Ru(η2:η4‐1,3,7‐octatriene)]+, [(OC)Fe(η4‐diene)(η5‐cycloheptadienyl)]+, and [CpCo(η5‐cyclodienyl)]+ give the nucleophilic adducts whereas with [Mn(CO)5]−, [W(CO)3Cp]−, and [Fe(CO)2Cp]− formation of the corresponding C‐C coupling products and of the metal‐metal‐bonded dimers is observed. The structures of Cp*Ru(μ‐η1:η2:η3‐1,5‐octadienyl)Re(CO)5 (4), [Cp* Ru(μ‐η1:η2:η3‐1,5‐octadienyl)]2Os(CO)4 (6), and of (OC)‐Fe(η4‐1,3‐cyclohexadiene) (μ‐η1:η4‐1,3‐cycloheptadiene)Re(CO)5 (9) have been determined by X‐ray diffraction.
Über Metallalkyl‐ und ‐aryl‐Verbindungen, 53. Synthese und Struktur von [9,10‐Dihydroanthracenylnatrium(tmeda)]n und [9,10‐Dihydroanthracenylnatrium(pmdta)] (tmeda = Tetramethylethylendiamin, pmdta = Pentamethyldiethylentriamin)
Authors: Viebrock Heiko , Behrens Ulrich , Weiss Erwin 
Published: July 2007

On Alkyl‐ and Arylmetall Compounds, 53[11]. ‐ Synthesis and Structure of [9,10‐Dihydroanthracenylsodium(tmeda)]n and [9,10‐Dihydroanthracenylsodium(pmdta)] (tmeda = tetramethylethylenediamine, pmdta = pentamethyldiethylenetriamine)The metalation of 9,10‐dihydroanthracene with n‐butylsodium (nBuNa) in the presence of the N bases Me2‐NCH2CH2NMe2 (tmeda) and Me2NCH2CH2N(Me)CH2‐CH2NMe2 (pmdta) yields the solvated 9,10‐dihydroanthracenylsodium‐base adducts 1 and 2, respectively. According to X‐ray diffraction studies the tmeda adduct 1 is a linear polymer in the solid state whereas the pmdta adduct 2 is monomeric.
Stereoselektive Protonierung von Carbanionen, 3. 1,3‐Dioxolan‐4‐one und 1,3‐Oxazolidin‐4‐one: Synthesen und diastereoselektive Protonierung ihrer Anionen
Authors: Hünig Siegfried , Keita Yango , Peters Karl , von Schnering Hans‐Georg 
Published: July 2007

Stereoselective Protonation of Carbanions, 3. — 1,3‐Dioxolan‐4‐ones and 1,3‐Oxazolidine‐4‐ones: Syntheses and Diaste‐reoselective Protonation of their AnionsDioxolonanones 3 and oxazolidinones 4 are synthesized by different methods together with the silyl enol ether 3asi. The configuration of their diastereomers is determined by 1H‐NMR spectroscopy and relative retention times (vpc), backed by a crystal structure analysis of cis‐3d. Protonation of 3aLi and 4aLi by different OH and CH proton sources in THF at ‐78°C occurs by kinetic product control yielding always ca. 70–90% of the cis isomers. Exchange of the cation in 3Li by potassium or addition of several Lewis acids does not effect the cis/trans relations. Obviously, even the steric effect of a methyl group in 2‐position of 3Li and 4Li dominates so strongly that the effect of other parameters are suppressed.
Thermisch kontrollierte oxidative Lineartrimerisierung von Alkinylgruppen in (Trimethylphosphan)nickel‐Komplexen: Strukturen und die Rolle ligandreicher Vorstufen NiX(CCR)PMe3)n (n = 2–4)
Authors: Klein Hans‐Friedrich , Zwiener Monika , Petermann Andreas , Jung Thomas , Cordier Gerhard , Hammerschmitt Birgit , Flörke Ulrich , Haupt Hans‐Jürgen , Dartiguenave Yves 
Published: July 2007

AbstractOxidative Linear Trimerization of Alkynyl Groups in (Trimethylphosphane)nickel Complexes: Structures and the Role of Ligand‐Rich Precursors NiX(CCR)(PMe3)n (n = 2–4)Oxidative additions of 1‐halogenoalkynes XCCR; to Ni(PMe3)4 afford high yields of pentacoordinate ionic alkynylnickel compounds [Ni(CCR)(PMe3)4]+X− [R = SiMe3, X = I (1); R = CMe3, X = I (2), Br (3); R = SiEt3, X = I (6), Br (7); R = SiiPr3, X = I (10), Br (11), R = Ph, X = I (21), Br (22)] or complex molecules Ni(CCR)X(PMe3)3 [R = SiPh3, X = I (14), Br (15); R = Ph, X = I (19), Br (20)]. Dissociation of trimethylphosphane gives square planar trans‐Ni(CCR)X‐(PMe3)2 [R = CMe3, X = Br (4), Cl (5); R = SiEt3, X = Br (8), Cl (9); R = SiiPr3, X = Br (12), Cl (13); R = SiPh3, X = I (16), Br (17), Cl (18); R = Ph, X = I (23), Br (24), Cl (25)] but with R = SiR'3, X = I the title reaction dominates with formation of trans‐Ni[C(CCR)=CR(CCR)]I(PMe3)2 [R = CMe3 (26), SiEt3 (29), SiiPr3 (32)]. Thermal activation is necessary in order to obtain trans‐Ni[CCR)=CR(CCR)]X(PMe3)2 [R = CMe3, X = Br (27), Cl (28); R = SiEt3, X = Br (30), Cl (31); R = SiiPr3, X = Br (33), Cl (34)], while only thermal decomposition is observed with trans‐Ni(CCR)X(PMe3)2 (R = Ph, SiPh3). Examples for both types of reactivity including structural data are given: trans‐Ni(CCRSiMe3)Br(PMe3)2 and 25 crystallize in the space group P1. Pentacoordinate 19 (space group P21) adopts a trigonal pipyramid of ligand donor atoms with equatorial phenylethynyl and iodo ligands.
1,3,5‐Cyclohexatrien‐1,4‐diyl und 2,4‐Cyclohexadien‐1,4‐diyl
Authors: Roth Wolfgang R. , Hopf Henning , Horn Carina 
Published: July 2007

AbstractThe Energy Well of Diradicals, V[1]. — 1,3,5‐Cyclohexatriene‐1,4‐diyl and 2,4‐Cyclohexadiene‐1,4‐diylThe energy profile of the Bergman rearrangement of (Z)‐3‐hexene‐1,5‐diyne (4) has been established from the NO and oxygen dependance of the trapping rate of the intermediate diradical 1 which leads to a heat of formation for 1,4‐didehy‐drobenzene (1) of δHOf= 138.0 ± 1.0 kcal . morl−1. By the same technique the heat of formation of 1,2,4‐cyclohexatriene (2), generated by thermolysis of (Z)‐1,3‐hexadien‐5‐yne (10), gives δHOf = 105.1 ± 1.0 kcal . mol−1 which indicates a high diradical character for 2.
Palladium‐Catalyzed Coupling of Vinylferrocene with Aromatic Halides — A Highly Efficient Route to (Ferrocenylvinyl)arenes
Authors: König Burkhard , Zieg Harald , Bubenitschek Peter , Jones Peter G. 
Published: July 2007

Abstract(Ferrocenylvinyl)arenes 3, 5, and 7 are obtained from vinylferrocene (1) and substituted aromatic and heteroaromatic halides by palladium‐catalyzed Heck‐type reactions. Up to three ferrocene units are introduced in one step by the multi‐fold reaction of 1,2‐dibromo‐ (4) or 1,3,5‐tribromobenzene (6) with 1. The first crystal structure of a bis(ferrocenylvinyl)benzene chromophore (5) is reported.
Chirale Tripod‐Liganden: Ein neuer Syntheseweg zu chiralen, C1‐symmetrischen Neopentyltris(phosphan)‐Liganden H3CC[CH2P(Ra)2][CH2P(Rb)][CH2P(Rc)2]
Authors: Seitz Thomas , Muth Andreas , Huttner Gottfried 
Published: July 2007

Chiral Tripod Ligands: A New Synthetic Route to Chiral C1‐symmetrical Neopentyltris(phosphane) Ligands H3CC[CH2P(Ra)2][CH2P(Rb)2][CH2P(Rc)2]A novel synthesis of chiral tripod ligands H3CC[CH2P‐(Ra)2][CH2P(Rb)2][CH2P(Rc)2] (6) containing three different donor groups at their neopentyl backbone is described. The key intermediates H3CC[CH2P(Ra)2][CH2P(Rb)2](CH2OH) (3) are easily obtained starting from pentaglycerine, H3CC‐(CH2OH)3, via the oxetanes (2) following published procedures. The compounds 3, after protection of the phosphane functions by BH3 {formation of H3CC[CH2P(Ra)2BH3][CH2P(Rb)2BH3](CH20H) (4)} are transformed into the mesylates H3CC[CH2P(Ra)2BH3][CH2P‐(RB)2BH3](CH20Ms) (5), which upon reaction with KP(Rc)2 and deprotection with morpholine gives fair yields of racemic 6. The synthetic route described is thus a valuable and efficient alternative to a recently published procedure, based on H3CC(CH2CI)(CH2Br)(CH20S02CF3) as the key intermediate. The compounds 2–6 are obtained in analytically pure form and are fully characterised by spectroscopic data.
Darstellung und Charakterisierung tellurhaltiger Chalkogen‐Stickstoff‐Fünfringsysteme — Struktur von [ClTeNSNS+]2[Cl‐][AsF‐6]
Authors: Haas Alois , Pryka Michael , Schäfers Mike 
Published: July 2007

Preparation and Characterisation of Five‐Membered Tellurium‐Containing Chalcogen‐Nitrogen Ring Systems — Structure of [ClTeNSNS+]2[Cl‐][AsF‐6]The reaction of [(Me3Si)2N]2S with TeX4/SeCl4‐ or TeX4/SCl2 mixtures leads to the formation of covalent five‐membered and , respectively. Treatment of 2a and 2b with Ag+Y‐ (Y‐ = BF‐4, AsF‐6, SbF‐6) in liquid SO2 provides the cationic ring systems and 3d–f (X = Br). If the solvent is CH2Cl2 the double salts and 4d–f (X = Br) are obtained. The structure of has been determined by X‐ray crystallography. The selenium‐containing five‐membered ring systems are accessible by reaction of AgAsF6 with 1a and 1c, respectively.
Oxidationsreaktionen mit HOF sowie Addukte von HOF und HF mit Acetonitril
Authors: Dunkelberg Oliver , Haas Alois , Klapdor Martin Frank , Mootz Dietrich , Poll Wolfgang , Appelman Evan Hugh 
Published: July 2007

Oxidation Reactions with HOF and Adducts of HOF and HF with AcetonitrileIn acetonitrile solution HOF oxides CF3SSCF3 via CF3S(O)nSCF3 (n = 1, 2) to yield [CF3S(O)2]2O. Analogously, CF3Se(O)OH and CF3SeX (X = Cl, Br) are oxidized via CF3Se(VI) intermediates to provide finally [CF3Se(O)2]2O. With CH3CN at low temperatures HOF and HF form 1:1 adducts, whose structures have been elucidated by low‐temperature X‐ray structure analysis. Additional proof for the formation of CH3CN · HF in the liquid phase is provided.
Phosphanylsubstituierte 1,2‐Azaborole
Authors: Schmid Günter , Reschke Jürgen , Boese Roland 
Published: July 2007

1,2‐Azaborolyl Complexes, XXX[1]. — Phosphanyl‐Substituted 1,2‐Azaboroles1‐tert‐Butyl‐2‐methyl‐1,2‐azaborolyllithium (LiAb, 1) and TlCl equilibrate at ‐75°C in THF under action of light to TlAb (2) and LiCl. Compound 2 decomposes above ‐50°C with elimination of thallium and the neutral isomers 1‐tert‐butyl‐2,5‐dihydro‐2‐methyl‐1H‐1,2‐azaborole and 1‐tert‐bu‐tyl‐2,3‐dihydro‐2‐methyl‐1H‐1,2‐azaborole. Whilst 1 reacts with Ph2PCl in only very small amounts to give the expected Ph2P‐substituted azaborole ring 3, TlAb (2) forms this compound by reaction with Ph2PCl in high yields. The yellow oily 3 is characterized by 1H‐; 11B‐, 13C‐, and 31P‐NMR data. The Me3Si‐substituted derivative 1‐tert‐butyl‐3‐(diphenyl‐phosphanyl)‐2,3‐dihydro‐2‐methyl‐3‐(trimethylsilyl)‐1H‐1,2‐azaborole (5), available via 4, the Li salt of 3, and ClSiMe3, forms yellow crystals which could be used for an X‐ray structure analysis. As expected, the Ph2P and Me3Si groups substitute the boron neighboring C3 atom of the planar ring framework. The crystal structure of 5 shows the two expected enantiomers.
Enantioselektive Protonierung von γ‐Butyrolacton‐Enolaten
Authors: Gerlach Uwe , Haubenreich Thomas , Hünig Siegfried , Klaunzer Norman 
Published: July 2007

Stereoselective Protonation of Carbanions, 6[1]. — Enantioselective Protonation of γ‐Butyrolactone Enolates*The lithium enolates 3Li–7Li, produced from 3–7 by LDA or LiHMDS in THF, are protonated with eleven chiral proton sources at ‐78°C in THF which produced high enantioselectivities with 1Li and 2Li[5]. Although the enolates (3Li, 6Li, 7Li) are not deuterated quantitatively[1], 1H‐ and 13C‐NMR spectra in THF at ‐78°C reveal not only quantitative deprotonation (3Li, 6Li) but also aggregation (dimerisation) and hindered rotation of the phenyl group in 3Li. From comparison of the enantioselectivities produced by five chiral proton sources with 1Li–6Li (Tab. 4) definite structure/selectivity correlations can not be derived both for the enolates and the proton sources.
Ein neues, Deltaphan und bandförmige Cyclophane
Authors: Josten Wolfgang , Neumann Susanne , Vögtle Fritz , Nieger Martin , Hägele Klaus , Przybylski Michael , Beer Frank , Müllen Klaus 
Published: July 2007

A New Deltaphane and Ribbon‐Shaped CyclophanesThe reaction of the fourfold functionalized [3.3][3.3]metacyclophane 8 with tosylamide monosodium salt leads to a new deltaphane in quantitative yield. An X‐ray analysis confirms the belt‐shaped structure of 3. Moreover, a series 10–15 of well‐soluble belt‐shaped macrocycles with up to 21 interconnected benzene rings were detected. The intermediate [3.3][3.3]metacyclophane 4 shows remarkably short distances to enclosed toluene, one toluene molecule acting twice as a π acceptor and once as a π donor. Competition experiments with benzene demonstrate the dependence of conformational behaviour on the solvent.
Metallorganische Verbindungen der Lanthanoide, 91[1] Carben‐Addukte des zweiwertigen Samariums und Ytterbiums
Authors: Schumann Herbert , Glanz Mario , Winterfeld Jörn , Hemling Holger , Kuhn Norbert , Kratz Thomas 
Published: July 2007

Organometallic Compounds of the Lanthanides, 91[1]. ‐ Carbene Complexes of Divalent Samarium and Ytterbium(Imidazol‐2‐ylidene)lanthanide adducts (C5Me4Et)2Sm–CN‐(iPr)CMeCMeN(iPr) (5b), (C5Me5)2Yb–CN(Me)CMeCMeN(Me) (6a), (C5Me5)2Yb–CN(iPr)CMeCMeN(iPr) (6b), and (C5H3tBu2)2Yb–CN(Me)CMeCMeN(Me) (7a) are obtained from 1,3,4,5‐tetramethyl‐imidazol‐2‐ylidene (4a) or 1,4‐diisopropyl‐2,3‐dimethylimidazol‐2‐ylidene (4b) and (C5Me4Et)2Sm(THF) (1), (C5Me5)2Yb(THF) (2), or (C5H3‐tBu2)2Yb(THF) (3). The molecular structure of the ytterbium carbene complex 7a has been determined by X‐ray diffraction.
Substituierte N,N‐Chelat‐Liganden ‐ Anwendungen in der Molybdän‐katalysierten Olefin‐Epoxidation
Authors: Thiel Werner Richard , Angstl Michaela , Priermeier Thomas 
Published: July 2007

AbstractSubstituted N,N‐Chelate Ligands ‐ Applications in Molybdenum‐Catalyzed Epoxidation of Olefins*Oxodiperoxomolybdenum complexes 4 of substituted 2‐[3(5)‐pyrazolyl]pyridines (2a‐g) were synthesized in order to control the solubility of these complexes in organic solvents. Alkyl side chains (butyl, octyl, octadecyl) increase the solubility of the complexes and enable spectroscopic investigations in solution. Due to the symmetry of the ligands the peroxo complexes 4 appear in two isomeric forms, with the terminal oxo ligand in the trans position either to pyridine or to pyrazole. The latter isomer of (C5H4NC3H2N2CH2COOEt)MoO(O2)2 (4f) was characterized by an X‐ray structure analysis. The alkyl‐substituted peroxo complexes are active catalysts for the epoxidation of olefins with tert‐butyl hydroperoxide.
Pyrazolylborat‐Zinkkomplexe mit Medikament‐Liganden
Authors: Hartmann Uwe , Vahrenkamp Heinrich 
Published: July 2007

Pyrazolylborate‐Zinc Complexes with Drugs as LigandsThe model complexes for hydrolytic zinc enzymes L3Zn‐OH with L3a = tris(3‐tert‐butyl‐5‐methylpyrazolyl)borate and L3b = tris(3‐cumyl‐5‐methylpyrazolyl)borate (1a, b) were tested for their interaction with drugs. With acetazolamide (HAcm) the complex L3bZn‐Acm (2b) is obtained which according to a structure determination contains the Acm ligand chelating by one azole and the sulfonamide nitrogen atoms. Furosemide (HFur) forms the two complexes L3Zn‐Fur (3) which according to their spectra contain the furosemide anion as a monodentate carboxylate ligand. Aspirin (AcSalH) is saponified by both L3Zn‐OH complexes yielding L3Zn‐Sal (4). The structure determination of L3bZn‐Sal (4b) has shown the salicylic acid to be bound as a monodentate carboxylate as well.
Photochemische und thermische Erzeugung von Thiocarbonylyliden aus 2,5‐Dihydro‐1,3,4‐thiadiazolen
Authors: Mloston Grzegorz , Romanski Jaroslaw , Schmidt Christiane , Reisenauer Hans Peter , Maier Günther 
Published: July 2007

Photochemical and Thermal Generation of Thiocarbonyl Ylides from 2,5‐Dihydro‐1,3,4‐thiadiazoles[*]Thermolysis of thiadiazolines 2a‐c yields the corresponding thiiranes 5a‐c exclusively. In contrast matrix photolysis in an organic glass at 77 K or in solid Ar at 10 K allows the detection of the thiocarbonyl ylides 3a‐c, which are characterized by intense UV maxima at λ ≈ 350 nm. The thiocarbonyl ylides are formed in a stepwise manner and not directly from the thiadiazolines by a simple elimination of N2. In the first step a fragmentation into the thioketones 6a‐c and diazomethane occurs, followed by the generation of methylene (8) from diazomethane (7). Addition of methylene to the thioketones 6a‐c finally leads to the ylides 3a‐c.
(η3‐Allyl)(η5‐pentamethylcyclopentadienyl)cobalt ‐ ein selektiver Katalysator für die Pyridinsynthese
Authors: Nehl Hans 
Published: July 2007

(η3‐Allyl)(η5‐pentamethylcyclopentadienyl)cobalt – a Selective Catalyst for the Pyridine Synthesis(η3‐Allyl)(η5‐pentamethylcyclopentadienyl)cobalt (1) catalyses the synthesis of various pyridines from alkynes and nitriles under mild conditions. Only small amounts of benzenes are formed in this selective reaction.