bluuebunny/crossref_metadata_2025 huggingface dataset:
From Azole—Borane Adducts to Azaboles — Molecular Structure of an Imidazabole
Authors: Padilla‐Martinez Itzia I. , Rosalez‐Hoz Maria De Jesus , Contreras Rosalinda , Kerschl Susanna , Wrackmeyer Bernd
Published: July 2007

Elimination of H2 from the imidazole—borane adduct 1 leads to a mixture of the imidazaboles 2 and 2′. The symmetrical isomer 2 (two H2BNC fragments) is isolated in pure state and characterized by an X‐ray structure analysis (monoclinic, space group P21). 2‐(Trimethylstannyl)thiazole (3a) and 1‐methyl‐5‐(trimethylstannyl)‐1,2,4‐triazole (3b) react with triethylborane to form adducts 4 from which, in the presence of an excess of Et3B, tetraalkyltin is elimated to give the thiazabole 5a and the triazabole 5b, respectively. Multinuclear 1H‐, 11B‐, 13C‐, 14N‐, and 119Sn‐NMR spectroscopy serve for following the reactions (compounds 3 to 5) and to characterize all final products.
Stereoelektronische Effekte und chirale Erkennung, I. Diastereoselektive Etherbildungen aus Alkylarylcarbinolen
Authors: Noe Christian R. , Knollmüller Max , Dungler Karin , Miculka Christian
Published: July 2007

Stereoelectronic Effects and Chiral Recognition, I. — Diastereoselective Formation of Ethers from Alkylarylcarbinols

Acid‐catalysed etherification of various alkylarylcarbinols 1 leads to a mixture of diastereomeric products 2 and 3. As found in the closely related formation of diastereomeric acetals, the ratio 2/3 is shown to be time‐dependent. Preferred formation of the meso‐diastereomer 3 under kinetic condition and preferred formation of the racemic diastereomer 2 under thermodynamic conditions is observed. A reaction path based on π‐π interactions and stereoelectronic effects is presented to explain experimental results.
Synthesis and Characterization of Soluble Oligo(9,10‐anthrylene)s
Authors: Müller Uwe , Adam Martin , Müllen Klaus
Published: July 2007

A homologous series of oligo(9,10‐anthrylene)s up to the heptamer have been synthesized by reductive coupling of quinones with lithioanthrylenes, followed by reductive aromatization of the intermediate hydroxy species. The method used allows the introduction of different alkyl substituents, which ensure sufficient solubility of the newly synthesized anthrylene systems in common organic solvents. The solid‐state conformations of trimers4and5have been established by X‐ray structure analysis; UV/Vis‐spectroscopic investigations in solution reveal the anthracene moieties in 9,10‐anthrylenes to exist as electronically independent electrophores. The trianthrylenes can be subjected to electrophilic substitution which regioselectively provides e.g. 10‐bromo‐ and 10,10″‐dibromo derivatives. These bromides can easily be converted into the corresponding cyano compounds. Under the influence of potassium hydroxide in quinoline the trimer5partially cyclizes to helianthrene compounds.
Synthese und Koordinationschemie hemilabiler P,N‐Hybridliganden mit terminalen 2‐Pyridyl‐Donorgruppierungen
Authors: Heßler Antonella , Fischer Jörg , Kucken Stefan , Stelzer Othmar
Published: July 2007

Synthesis and Coordination Chemistry of Hemilabile P,N‐Hybride Ligands with Terminal 2‐Pyridyl Donor Groups*

P,N‐hybride ligands 1–7 containing terminal 2‐pyridyl donor groups have been obtained by base‐catalyzed addition of diphenylvinylphosphane or 2‐vinylpyridine to primary or secondary phosphanes [2‐Py‐(CH2)2‐PR′H (R′ = H, Ph), HMeP‐(CH2)3‐PMeH] or by alkylation of organolithium phosphides, R2P‐(CH2)3‐PMeLi or 2‐Py‐(CH2)2‐PR′Li (R = Ph, iPr; R′ = H, Ph), with 2‐(2‐chloroethyl)pyridine or di‐tert‐butylphosphetanium bromide. Upon reaction with NiBr2 3 H2O or K2MCl4 (M = Pd, Pt) the phosphanes (L) of type 2‐Py‐(CH2)2‐P(R′)‐(CH2)m‐PR2 (1, 3, 6) form square planar Ni(II), Pd(II), and Pt(II) complexes of composition MX2(L) (10–14). With NiBr2 and K2MX4 the tripod type phosphane 2 forms square pyramidal complexes [MX(2)]X (M = Ni, Pd; X = Cl, Br; 15, 16). An X‐ray structural analysis of [NiBr(2)]+Br− (15) reveals a distorted square pyramidal coordination geometry at Ni(II), the 2‐Py donor being in apical position with a long NiN bond [2.270(15) Å]. The tetradentate ligand 7 forms Ni(II), Pd(II), and Pt(II) complexes MX2(7) which for M = Pd, Pt show dynamic behaviour by exchange of the terminal Py donor groups. With [RhCl(COD)]2 the tridentate ligands L (1 and 3) yield complexes of composition RhCl(L) (20, 21). The structure of 20 has been determinated by X‐ray diffraction. The ligand 3, acting in a tridentate manner, is coordinated to Rh(I) in a distorted square‐planar arrangement with a normal RhN distance [2.145(3) Å].
Photolyse von Naphth[2,3‐d]‐1,2,3‐oxadiazol — Ein Beitrag zum Oxiren‐Problem
Authors: Blocher Achim , Zeller Klaus‐Peter
Published: July 2007

Photolysis of Naphth[2,3‐d]‐1,2,3‐oxadiazole — A Contribution to the Oxirene Problem

The photolysis of [9a‐13C]naphth[2,3‐d]‐1,2,3‐oxadiazole ([9a‐13C]14) in methanol, water, and cyclohexane is studied. In the protic solvents, the Wolff rearrangement products 2‐(methoxycarbonyl)indene ([13CO]16) and 2‐indenecarboxylic acid ([13CO]23) exclusively labelled at the carbonyl carbon are obtained. Furthermore, the photolysis of [9a‐13C]14 in methanol yields [2‐13C]‐2‐naphthol (19) as hydrogen abstraction product. The photolytic decomposition of 14 in cyclohexane affords 2‐(2‐naphthoxycarbonyl)indene (25) and 1‐cyclohexyl‐2‐(2‐naphthoxycarbonyl)indene (26). The formation of 25 is explained by nucleophilic addition of 2‐naphthol (19) to the intermediate ketene 21. 2‐Naphthol (19) is generated in situ by hydrogen abstraction from cyclohexane. The cyclohexyl radicals, thereby obtained, convert 25 to 26. Similar photolysis of [9a‐13C]14 affords [13CO13CO]25 and [13CO13CO]26 labelled at the carbonyl carbon and C‐2 of the naphthalene ring. Thus, independent of the nature of the solvent (methanol, water, cyclohexane), no labelling distribution is found in the photolysis products of [9a‐13C]14. This excludes the participation of naphth‐[2,3‐b]oxirene (17) as reactive intermediate.
Synthesen und Reaktionen acyclischer fluororganischer Thiocarbenium‐Ionen
Authors: Boese Roland , Haas Alois , Krüger Carl , Möller Guido , Waterfeld Alfred
Published: July 2007

Syntheses and Reactions of Fluoroorganic Acyclic Thiocarbenium Ions

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

Arsenic pentafluoride oxidizes (F3CS)4C (1) but not (F3CS)2C = C(SCF3)2 (2) to yield the stable salt (F3CS)3C+AsF‐6 (3). It reacts with halide ions to form (F3CS)3CX (3a–c, X = F, Cl, Br). Iodide is oxidized to iodine with formation of (F3CS)3CC(SCF3)3 (4) which reacts with nitrogen dioxide to give (F3CS)3CNO2 (3e). ‐ (F3CS)3C+AsF‐6 (3) removes from (F)‐SCF3 (5a) a ring‐bound fluorine atom to afford (F3CS)3CF and magnified image‐SCF3]+AsF−6 (5). When (F3CS)3CCl (3b) is treated with AsF5, 3 and [(F3CS)2‐CCl]+AsF−6 (6) are formed in a 2:1 molar ratio. The latter reacts with F− or Cl− to give (F3CS)2CClX (6a,b; X = F, Cl). AsF5 is capable of abstracting a fluoride ion from (F3CS)3 ‐ n Cln,CF only if n = 0 or 1. For n = 2 no similar reaction takes place, but with AlCl3 in BCl3 halogen exchange to F3CSCCl3 (7b) is observed. ‐ Alkylation of (F3CS)2CS (8) with H3CF/AsF5 yields [(F3CS)2CSCH3]+AsF−6 (9), which adds a fluoride ion to give (F3CS)2(H3CS)CF (9a). The molecular structures of (F3CS)2C = C(SCF3)2 (2) and (F3CS)3CC(SCF3)3 (4) have been determined by X‐ray diffraction methods.
Diastereoselective Radical Bromination of 5,6‐Dihydro‐4H‐1,2‐oxazines and Subsequent Substitution Reactions with Nitrogen Nucleophiles
Authors: Paulini Klaus , Reißig Hans‐Ulrich
Published: July 2007

5,6‐Dihydro‐4H‐1,2‐oxazines 1a‐b, 2, and 3 are easily brominated at C‐4 with N‐bromosuccinimide/dibenzoyl peroxide in tetrachloromethane. The bromo substituent is incorporated with surprisingly high diastereoselectivity trans to the substituent at C‐6. 4‐Bromo‐5,6‐dihydro‐4H‐1,2‐oxazines are useful reagents for substitution reactions with N‐nucleophiles such as primary amines and azide ions. Inversion of configuration at C‐4 provides derivatives of 4‐amino‐1,2‐oxazines with uniform relative configuration. As a minor byproduct the dibromo adduct 7 is obtained by bromination of 3. The dehydrohalogenation of this compound allows the synthesis of the 4‐bromo‐6H‐1,2‐oxazine 12. The presented reaction sequence thus constitutes an “umpolung” reaction that allows the introduction of nucleophiles into a position of the oxazine ring that so far was accessible only for electrophiles. The diastereoselectivity of the bromination reaction is discussed.
Substituenteneffekte auf die CC‐Bindungsstärke, 14. Kinetische und thermodynamische Stabilität von 2,3‐Bis(dialkylamino)‐1,4‐diketonen — Stabilisierungsenergie capto‐dativ substituierter a‐Dialkylamino‐a‐Carbonylalkyl‐Radikale
Authors: Welle Frank , Verevkin Sergej P. , Keller Manfred , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

Substituent Effects on the Strength of CC Bonds, 14[1]. — Kinetic and Thermodynamic Stability of 2,3‐Bis(dialkylamino)‐1,4‐diketones — Energy of Stabilization of α‐Dialkylamino α‐Carbonylalkyl Radicals with Capto‐dative Substituents

Prof. Dr. H.‐G. Viehe zum 65. Geburtstag gewidmet.

The equilibrium constants and rate constants for the dissociation of the 2,3‐bis(dialkylamino)‐1,4‐diketone diastereomers meso‐ and DL‐7a and 7b were measured over a temperature range of 40°C. From the enthalpies of dissociation ΔHDiss and enthalpies of activation ΔH≠ and the strain enthalpies of 7 the bond dissociation enthalpies BDE(CC) of 7 were determined. By comparison with the dissociation enthalpies of Ct‐Ct alkanes[21] the change of these BDEs(CC) by the cap‐to‐dative substitution was determined to be 85.4 kJ mol−1 (20.4 kcal mol−1). The heats of formation ΔH (g) of a series of amino ketones 8 were determined from their heats of combustion and their heats of evaporation. From the ΔH(g) values in combination with MM2 calculations of their strain enthalpies strain‐free increments CHn[N, CO, C2 ‐ n] with n With n = 0, 1, 2 were derived and geminal interaction enthalpies in the ground states were obtained thereof. The radical stabilization enthalpy RSE of 6 was deduced from the ΔBDE(CC) values and the ground state effect to be 73.6 kJ mol−1 (17.6 kcal mol−1). From these data and the radical stabilization enthalpies RSE of α‐aminoalkyl radicals (4.2 kJ mol−1) and α‐carbonyl radicals (28.9 kJ mol−1) a synergetic radical stabilization enthalpy of 40.5 kJ mol−1 (9.7 kcal mol−1) is deduced. This number combines “extra” resonance stabilization and general inductive or anomeric geminal substituent interaction in the radicals. The crystal structure of meso‐7a has been determined by X‐ray diffraction methods.
Organische Synthesen mit Übergangsmetallkomplexen, 70. [2‐(Galactopyranosylamino)ethenyl]carben‐ und 3‐(Galactopyranosylamino)‐1,2‐propadienyliden‐Komplexe durch 3‐Addition von 2,3,4,6‐Tetra‐O‐pivaloyl‐β‐D‐galactopyranosylamin an Alkinylcarben‐Komplexe (M = Cr, W). — Atropisomere Galactopyranosyl‐Pyrrole durch Reaktion von [2‐(Galactopyranosylamino)ethenyl]carben‐Komplexen mit Isocyaniden
Authors: Aumann Rudolf
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 70[1]. — [2‐(Galactopyranosylamino)ethenyl]carbene and 3‐(Galactopyranosylamino)‐1,2‐propadienylidene Complexes on 3‐Addition of 2,3,4,6‐Tetra‐O‐pivaloyl‐β‐D‐galactopyranosylamine to Alkynylcarbene Complexes (M = Cr, W). — Atropisomeric Galactopyranosyl Pyrroles by Reaction of [2‐(Galactopyranosyl‐amino)ethenyl]carbene Complexes with Isocyanides

Enantiomeric pure (2‐aminoethenyl)carbene complexes LnMC(OEt)CHC(Ph)NHR* (Z)‐3 and 3‐amino‐1,2‐propadienylidene complexes LnMCCC(Ph)NHR* 4 [R* = 2,3,4,6‐tetra‐O‐pivaloyl‐β‐D‐galactopyranosyl] are obtained by the addition of galactopyranosylamine R*‐NH2 2 to the corresponding alkynylcarbene complexes LnMC(OEt)CCPh 1 [LnM = (CO)5Cr, (CO)5W]. Treatment of (Z)‐3 with two equivalents of tert‐butyl isocyanide (5) affords isocyanide complexes 6 and ketene imines 7. The latter cyclize spontaneously to give galactopyranosylpyrroles 8 which form stable atropisomers 8A and 8B.
Photoreaktionen mit Fulleren‐C60 [3 + 2]‐Photocycloaddition von 2,3‐Diphenyl‐2H‐azirin
Authors: Averdung Johannes , Albrecht Evelyn , Lauterwein Jürgen , Luftmann Heinrich , Mattay Jochen , Mohn Holger , Müller Wolfgang H. , Meer Hans‐Ulrich Ter
Published: July 2007

Photoreactions with C60‐Fullerene. [3 + 2] Photocycloaddition of 2,3‐Diphenyl‐2H‐azirine

Upon irradiation 2,3‐Diphenyl‐2H‐azirine (2) is added to C60 1 with formation of mono and oligo adducts. 1,9‐(3,4‐Dihydro‐2,5‐diphenyl‐2H‐pyrrolo)fulleren‐60 (3) has been isolated and identified by standard spectroscopic methods. Mechanistic studies revealed two reaction paths leading to 3, i.e. the classic 1,3‐dipolar cycloaddition via the nitrile ylide 4 (direct irradiation) or a route via 2‐azaallenyl radical cations 5 (sensitization by photoinduced electron transfer).
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

Addition 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

When 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

From 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

Collision 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 Dyes

The 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.
N,N‐Bis(trimethylsilyl)ynamines: Cycloaddition Reactions with Dimethyl Acetylenedicarboxylate and Ketenes
Authors: Schulte Norbert , Möller Manfred H. , Rodewald U. , Würthwein Ernst‐Ulrich
Published: July 2007

N,N‐Bis(trimethylsilyl)ynamines 1 react with dimethyl acetylenedicarboxylate (2) in a molar ratio of 1:2 to afford 3‐cyclopropenylfurans 3. Configuration and conformation of 3a are confirmed by X‐ray crystallography. Addition of a further mol of 1 furnishes the fumarates 4. With ketenes 5 (5c, d are prepared in situ) a competition between the formation of cyclic butenone derivatives 6 and allenic imidates 7 is observed, depending on the substitution pattern of 1. After hydrolytic workup, the corresponding amides 10 or the vinylogous amides 9 are obtained in good yield. These experiments indicate that the silylated ynamines 1 show a completely different, more selective reactivity towards dimethyl acetylenedicarboxylate compared to N,N‐dialkyl‐substituted ynamines, yielding furan derivatives instead of anilines. Towards ketenes, however, a similar cycloaddition reactivity as for N,N‐dialkylynamines is observed.
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) Iodide

Ethyl (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.
A Synthetic Pathway to 1,3‐Bis(trisilylmethyl)disiloxane [(H3Si)3CSiH2]2O — the Octasila Analogue of Dineopentyl Ether [(H3C)3CCH2]2O
Authors: Bommers Sebastian , Schmidbaur Hubert
Published: July 2007

A synthetic route to partly silylated tetra(silyl)methanes (ArH2Si)nC(SiH3)4 — n′ to their precursors (TfH2Si)nC‐(SiH2Ar)4 — n (Ar = p‐tolyl, phenyl; Tf = CF3SO3; n = 3, 2, 1), and to 1,3‐bis(trisilylmethyl)disiloxane [(H3Si)3CSiH2]2O (9) is reported. Starting from symmetrical tetrakis(arylsilyl)‐methanes (aryl = p‐tolyl, phenyl), we have obtained the selectively dearylated (arylsilyl)silylmethanes (ArH2Si)nC(SiH3)4 — n (Ar = p‐tolyl, phenyl; n = 3, 2, 1) by Si—Ar cleavage with equivalent quantities of trifluoromethanesulfonic acid (triflic acid) and hydrogenation of the corresponding silyl triflates (TfH2Si)nC(SiH2Ar)4 — n (n = 3, 2, 1) with LiAlH4. The synthesis of 9 has been accomplished by treating trisilyl(p‐tolylsilyl)methane p‐TolH2SiC(SiH3)3 (7) with stoichiometric amounts of triflic acid to give (trisilylmethyl)silyl triflate TfH2SiC(SiH3)3 (8) and hydrolysing the latter with water.
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 Bridges

Herrn 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 Anions

Dioxolonanones 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.
Synthesis of a Novel Annulated C1‐Bridged ansa‐Metallocene System
Authors: Erker Gerhard , Psiorz Christian , Krüger Carl , Nolte Matthias
Published: July 2007

2,5‐Hexanedione (1) was converted into the bis(fulvene) 2, which was then treated with 2 molar equiv. of ethereal meth‐yllithium to give the novel annulated C1‐bridged dilithium bis(cyclopentadienide) 5. Reagent 5 was treated with MCl4 (M = Ti, Zr) to yield the annulated C1‐bridged ansa‐metallo‐cene dichlorides 6a and 6b, respectively. The homogeneous 6a, 6b/methylalumoxane Ziegler‐type systems were employed in propene polymerization reactions.
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

Oxidative 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

The Energy Well of Diradicals, V[1]. — 1,3,5‐Cyclohexatriene‐1,4‐diyl and 2,4‐Cyclohexadiene‐1,4‐diyl

The 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

(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 Acetonitrile

In 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.
Stannylalkynes as Starting Materials for the Synthesis of Vinylidene Rhodium Complexes and of Heterodimetallic Compounds Containing a Rh—Hg or Rh—Sn Bond
Authors: Baum Matthias , Mahr Norbert , Werner Helmut
Published: July 2007

Reaction of [RhCl(PiPr3)2]n (1) with stannylalkynes RCCSnPh3 [R = H, Me, Ph, CH2OH, CH2OMe, CMe2OH, CH(Me)OH, CH(Ph)OH, SiMe3, SnPh3] gives the vinylidenerhodium(I) complexes trans‐[RhCl(=C=C(SnPh3)R)(PiPr3)2] (2a–j) in good to excellent yields. These compounds react with protic acids to give trans‐[RhCl(CCHR)(PiPr3)2] and, for R = CH(Ph)OH, to give the allenylidene complex trans‐[RhCl(CCCHPh)‐(PiPr3)2] (5). On treatment of 2b–j with PhHgCl, the heterodimetallic compounds [Rh(CC̊)(HgPh)Cl(PiPr3)2] (6a–i) are formed. The bis(alkynyl)rhodium(III) complexes [RhH(CCSi‐Me3)(CCSnPh3)(py)(PiPr3)2] (9) and [Rh(CCSiMe3)(CCCH2OMe)(SnPh3)(PiPr3)2] (10) are prepared from trans‐[Rh‐(CCSiMe3)(L)(PiPr3)2] (7, 8, L = py, C2H4) and HCCSnPh3 or Ph3SnCCCH2OMe, respectively. The crystal and molecular structures of trans‐[RhCl(CC(SnPh3)CH2OMe)(PiPr3)2] (2e) and [Rh(CCCH2OMe)(HgPh)Cl(PiPr3)2] (6d) have been determined.
Phosphanylsubstituierte 1,2‐Azaborole
Authors: Schmid Günter , Reschke Jürgen , Boese Roland
Published: July 2007

1,2‐Azaborolyl Complexes, XXX[1]. — Phosphanyl‐Substituted 1,2‐Azaboroles

1‐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.
Hetero‐ansa‐Bridged Main Group Metallocenes — a Structural and NMR Study
Authors: Littger Ralf , Metzler Nils , Nöth Heinrich , Wagner Matthias
Published: July 2007

1,2‐Bis(dimethylamino)‐1,2‐di‐9‐fluorenyldiborane(4) (1) is doubly metallated with group 1 and 2 metals to yield metal 1,2‐bis(dimethylamino)‐1,2‐di‐9‐fluorenyldiborate(4) 2‐Li to 2‐Ba. The conformations of these compounds in solution are investigated by NMR spectroscopy, and the solid‐state structures of 2‐Li · 5 THF, 2‐K · 4 THF, 2‐K · 2 DME, and 2‐Ca · 2 THF are determined by X‐ray diffraction. All four structures can be described as main group metallocenes. The potassium derivatives form contact ion pairs, leading to polymeric chain‐like structures. In contrast, 2‐Li · 5 THF exhibits the rare combination of a contact ion pair with a solventseparated ion pair, giving the monomeric structure [Li(THF)4][(fl2B2(NMe2)2)Li · THF]. 2‐Ca · 2 THF, which is also monomeric, adapts a severely distorted geometry.
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.
Thermische Stabilität von 9,9′‐Bixanthen und 9,9′,10,10′‐Tetrahydro‐ 10,10,10′,10′‐tetramethyl‐9,9′‐bianthracen Stabilisierungsenergie planarer Benzhydryl‐Radikale[2]
Authors: Herberg Clemens , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

The thermal cleavage of the central CC bonds in the title compounds was investigated. The activation parameters were obtained from kinetics and the equilibrium enthalpies and entropies from the temperature dependence of the equilibrium radical concentrations, determined by quantitative ESR. ΔH≠ and ΔHDiss are nearly identical but not ΔS≠ and ΔSDiss, as expected. The radical stabilisation enthalpies RSE obtained from these data (RSE: 7a = 17.9 ± 1.3; 7b = 15.6 ± 1.4 kcal/mol) correspond closely to twice the RSE of α‐phenylethyl radicals (8.0 ± 1.5 kcal/mol) determined previously. The smaller RSE of the benzhydryl radical (12.9 ± 0.9 kcal/ mol), therefore, must be due to its nonplanarity.
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 Cyclophanes

The 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

Substituted 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 Ligands

The 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.
Tripodal Triamidostannates as Building Blocks in the Generation of Sn—M‐Bonded Heterobimetallics (M  Fe, Ru)
Authors: Hellmann Konrad W. , Friedrich Stefan , Gade Lutz H. , Li Wan‐Sheung , McPartlin Mary
Published: July 2007

By in situ lithiation of the trifunctional amines H3CC(CH2NHSiMe3)3, PhC(CH2NHSiMe3)3, and HC{SiMe2NH(p‐Tolyl)}3 and subsequent reaction with SnCl2 the corresponding triamidostannates were obtained. These were coupled with CpM(CO)2Cl (M  Fe, Ru) to yield the M—Sn‐bonded heterobimetallics 9–14 of which H3CC(CH2NSiMe3)3SnFe(CO)2Cp (9) was characterized by a single‐crystal X‐ray structure analysis. Of the in situ‐generated amidostannates only [HC{SiMe2N(p‐Tolyl)}3Sn][Li(THF)3] (8) could be isolated as a uniform product and characterized analytically and spectroscopically.
Synthese und Komplexchemie funktionalisierter Tripod‐Liganden RC(CH2PPh2)3
Authors: Janssen Bernd C. , Sernau Volker , Huttner Grottfried , Asam Alexander , Walter Olaf , Büchner Michael , Zsolnai Laszlo
Published: July 2007

Synthesis and Complex Chemistry of Functionalised Tripod Ligands RC(CH2PPh2)3Malonic ester 1 is alkylated and converted into the triols RC(CH2OH)3 (5). These are easily converted into the corresponding functionalised tripodal ligands RC(CH2PPh2)3 (7) with R  Bzl (a), n‐C12H25 (b), (CH3)2CH(CH2)2 (c). Crystals suitable for X‐ray crystallography have been obtained of the ligand 7a. In addition, the tripod ligands 7a and 7c have been further characterized by the syntheses and X‐ray analyses of the nickel complex [(7a)NiCl] (8a), the iron complex [(7c)Fe(NCCH3)3](BF4)2 [9 · (BF4)2], and the cobalt complex [(7c)Co{O(O)CCH3}](BPh4) (10 · BF4).
Hypercoordinate Carbon in Trigoldbis(silyl)methanium Cations
Authors: Bommers Sebastian , Beruda Holger , Dufour Nathalie , Paul Martin , Schier Annette , Schmidbaur Hubert
Published: July 2007

The reactions of organolithium compounds of the type (R3Si)2CHLi (R3 = Me3 or Me2Ph) with the gold(I) complex Ph3PAuCl afford the monoaurated bis(silyl)methanes (R3Si)2‐ CHAuPPh3 (1a, b) in high yield. These compounds are converted into complex salts with hypercoordinate methanium cations {(R3Si)2C[Au(PPh3)]3}+BF−4 (3a, b) by treatment with {[(Ph3P)Au]3O}+ BF−4. In the reaction mixtures small amounts of the neutral dinuclear intermediates {(R3Si)2C[Au(PPh3)]2} (2a, b) have been detected and characterized by their spectroscopic data. Compounds 1a, b and 3a, b have been studied by single crystal X‐ray diffraction analyses. While the mononuclear molecules 1a, b have conventional structures with parameters representing classical types of bonding, the novel trinuclear complexes 3a, b feature cations with a pentacoordinate carbon atom in a distorted trigonal‐bipyramidal environment of two silicon atoms and one gold atom in equatorial positions and the remaining two gold atoms at the axial vertices of the polyhedra. The main axis of the bipyramid is strongly bent at the central carbon atoms. This distortion leads to short axial/equatorial Au…Au distances indicating peripheral metal‐metal bonding.
Synthese von Carben‐Carbonyl‐Isonitril‐Komplexen von Chrom und deren Anellierungsreaktion mit Alkinen
Authors: Dötz Karl Heinz , Christoffers Carmen
Published: July 2007

Reactions of Complex Ligands, LXII[1]. – Synthesis of Carbene Carbonyl Isonitrile Complexes of Chromium and Their Annulation Reaction with Alkynes

1,1,3,3‐Tetramethylbutyl isocyanide (3a) and 2,6‐dimethylphenyl isocyanide (3b) react with the tetracarbonyl chelate carbene complex 2 to give the tetracarbonyl isocyanide carbene complexes 4a and 4b. Thermal decarbonylation leads to the tricarbonyl isocyanide chelate carbene complexes 5a and 5b. Upon reaction with 3‐hexyne they undergo an annulation to give the dicarbonyl indene complexes 6a and 6b.
Zwei Extreme in der Zinnchemie: Ein nichtbindender Sn–Sn‐Abstand von 285 pm und eine 119Sn‐NMR‐Verschiebung δ = 3301 in metallorganischen Derivaten von Sn(0)
Authors: Schiemenz Berthold , Huttner Gottfried , Zsolnai Laszlo , Kircher Peter , Diercks Tammo
Published: July 2007

Two Extremes in Tin Chemistry: A Non‐bonding Sn–Sn Distance of 285 pm and a 119Sn‐NMR Shift δ = 3301 in Organome‐tallic Derivatives of Sn(0)

The reaction of Na[{Cp'(CO)2Mn}2H] with SnCl2, which produces the inidene compound [Cp'(CO)2Mn\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ {\rm C}\ddot - {\rm C} $\end{document}Sn(Cl)\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ {\rm C}\ddot - {\rm C} $\end{document}Mn‐(CO)2Cp']− under standard workup procedures, results in the formation of [{Cp'(CO)2MnSn}2{μ2‐Mn(CO)2Cp'}2{μ2‐Cl}]− (1) when quenched with unpolar solvents. While, formally, 1 contains tin in its oxidation state zero, it may be conceived as composed of an Sn2−2 entity, which is linearly end‐on coordinated to two Cp'(CO)2Mn 16‐electron species; in addition the tin centers are bridged by two μ2‐Mn(CO)2Cp' moieties and a μ2‐Cl function. The resulting connectivity Sn2{μ2‐Mn(CO)2Cp'}2{μ2‐Cl} thus corresponds to a [1.1.1]propellane scaffolding. While there is no obvious need for a tin‐tin bond in this propellane‐type cage, a short Sn–Sn contact of only 285 pm is observed. While the 119Sn‐NMR signal of 1 could not be recorded, the peculiar bonding in this type of compounds is generally mirrored in their unconventional 119Sn‐NMR shift whereever signals can be observed: it is found that [{Cp*(CO)2Mn}3(μ3‐Sn)], which contains trigonally planar‐coordinated μ3‐Sn as a naked ligand atom, has its 119Sn‐NMR resonance at δ = 3301 well beyond the known range of 119Sn‐NMR shifts. This finding is interpreted in terms of a relatively week Snpπ‐Mndπ π bonding which leads to low‐energy unoccupied molecular orbitals as the prerequisit for a large paramagnetic contribution to the NMR shift.