bluuebunny/crossref_metadata_2025 huggingface dataset:
Organometall‐Imide – höhervalente Derivate der d‐Metall‐Säuren, 3. Synthese und Reaktionen von (Pentamethylcyclopentadienyl)(imido)‐Komplexen des Molybdäns und Wolframs und eine effiziente Strategie zur Synthese der Organometallate NBu4[Cp*MO3] (M = Mo, W)
Authors: Sundermeyer Jörg , Radius Udo , Burschka Christian
Published: July 2007

Organometallic Imido Complexes – Highervalent Derivatives of the d‐Metal Acids, 3[4b]. – Synthesis and Reactions of Pentamethylcyclopentadienyl Imido Complexes of Molybdenum and Tungsten and an Efficient Strategy for the Synthesis of the Organometallates NBu4[Cp*MO3] (M = Mo, W)

A convenient and new entry into the chemistry of highvalent pentamethylcyclopentadienyl halfsandwich complexes of molybdenum and tungsten is described. The reaction of Mo‐(NtBu)2Cl2 or W(NtBu)2Cl2(py)2 with Cp*Li (Cp* = η5‐C5Me5) provides a high‐yield route to new complexes Cp*Mo‐(NtBu)2Cl (1a) and Cp*W(NtBu)2Cl (1b) which are converted into a variety of diimido, monoimido, and oxo derivatives. Treatment of 1a,b with MeLi yields the highly volatile methyl derivatives Cp*Mo(NtBu)2Me (2a) and Cp*W(NtBu)2Me (2b), while protolysis of 1a,b with an excess of HCl gas leads to selective cleavage of only one imido function with formation of Cp*Mo(NtBu)Cl3 (3a) and Cp*W(NtBu)Cl3 (3b). In contrast, protolysis of 1a,b with aqueous HCl provides a high‐yield route to the well‐known organometallic oxides [Cp*MoO2]‐(μ‐O) (4a) and [Cp*WO2](μ‐O) (4b). These two key compounds are easily converted into the organomolybdate and organotungstate salts NBu4[Cp*MoO3] (5a) and NBu4[Cp*WO3] (5b) by cleavage of the M–O–M bridge with NBu4[OH]. The X‐ray structure of 3a is reported.
Trägerfixierte Organometallkomplexe, III. Polysiloxan‐gebundene (Ether‐phosphan)ruthenium(II)‐Komplexe und ihre CP‐MAS‐NMR‐spektroskopische Charakterisierung
Authors: Lindner Ekkehard , Kemmler Martin , Mayer Hermann August
Published: July 2007

Carrier‐Bound Organometallic Complexes, III[1]. – Polysiloxane‐Bound (Ether‐phosphane)ruthenium(II) Complexes and Their CP‐MAS NMR‐Spectroscopic Characterization

The reaction of the functionalized ether‐phosphane ligand CH3O(CH2)2P(Ph)(CH2)3Si(OMe)3 (1c) with Cl2Ru(PPh3)3 (2) and HRuCl(CO)(PPh3)3 (3) results in the formation of the mono‐chelated (ether‐phosphane)ruthenium(II) complex Cl2Ru(P∼O)2(P∼O) (4c) and the hydride HRuCl(CO)(P∼O)3 (5c) (P∼O: η1‐P‐coordinated; P∼O: η2‐O∼P‐coordinated). Compounds 4c and 5c are polycondensated to the corresponding polysiloxane‐bound complexes 4c′ and 5c′. 31P‐chemical shifts of the immobilized species 4c′ and 5c′ in the solid‐state CP‐MAS NMR spectra are compared with those of the 31P{1H}‐NMR spectra of monomeric complexes 4b, c and 5b, c with the ligands CH3O(CH2)2P(Ph)(CH2)3SiMe3 (1b) and 1c in solution. No change in the structure between the monomeric and polymeric species could be observed. According to 29Si CP‐MAS NMR‐spectroscopic investigations the polysiloxane chains are connected by ruthenium complexes to a network with favourable properties. The chelated polysiloxane‐bound red complex 4c′ adds CO in the solid state to give quantitatively yellow all‐trans‐Cl2Ru(CO)2(P∼O)2 (6c′). In the presence of carbon monoxide there is an equilibrium between 5c′ and HRuCl(CO)2(P∼O)2 (7c′) which was also found in solution for 5b, c and 7b, c. The reactions indicate that the chemistry of polysiloxane‐bound ether‐phosphane complexes can well be compared with the chemistry in solution. 31P CP‐MAS NMR spectra of the complexes 4c′ and 5c′ are strongly dominated by a chemical shift anisotropy which shows a fingerprint pattern both for monomeric crystalline complexes 4a, 5a [containing ligand Ph2P(CH2)2OCH3 (1a)] and polysiloxane‐bound phosphane complexes 4c′ and 5c′.
Transition‐Metal‐Catalyzed Oxidations, 5. Oxygenation of ortho‐Alkylated α‐ and ß‐Naphthols to α‐Ketols
Authors: Krohn Karsten , Brüggmann Kai , Döring Detlev , Jones Peter G.
Published: July 2007

The α‐ and ß‐naphthols 7a–7d, 8a and 8b are converted into the corresponding α‐ketols 9a–9c, 10a, 10b and 10d with concomitant dearomatization of ring A and partial shift of the alkyl group by reaction with tert‐butyl hydroperoxide in the presence of Ti(OiPr)4, Zr(acac)2 or [MoO(O2)2] py HMPT.
Base‐Induced Chemiluminescence of Acetoxy‐Substituted Benzofuran Dioxetanes by an Intramolecular Electron Transfer (CIEEL) Mechanism
Authors: Adam Waldemar , Schulz Manfred H.
Published: July 2007

Tetraphenylporphine‐sensitized photooxygenation of acetoxy‐substituted benzofuran derivatives 2 afforded the corresponding benzofuran dioxetanes 3. The base‐induced decomposition of these dioxetanes was studied and shown to involve an intramolecular CIEEL emission. The CIEEL chemiluminescence quantum yields were measured. The dioxetane 3e, in which the electron donor is located meta to the dioxetane site, exhibits the highest chemiluminescence of all derivatives investigated.
Photochemistry of N‐Phthaloyl α‐Amino Acid Esters: A New Approach to β,γ‐Unsaturated α‐Amino Acid, Dihydrobenzazepinedione, and Pyrrolizidinone Derivatives
Authors: Griesbeck Axel G. , Mauder Harald , Müller Ingrid
Published: July 2007

The N‐phthaloyl‐α‐amino acid methyl esters of 2‐aminobutyric acid (2a), valine (2b), norvaline (2c), tert‐leucine (2d), isoleucine (2e), allo‐isoleucine (2f), leucine (2g), methionine (2h), alanine (2i), and phenylalanine (2k) were synthesized in enantiomerically pure form via the N‐phthaloyl‐α‐amino acids (1a–k), and their photochemistry was studied. Except 2i and 2k, which proved to be photostable, all compounds were converted into three types of products, depending on the substitution pattern: a) isomerization products (derivatives of β,γ‐unsaturated α‐amino acids) 3a, b, c, and e, b) ring expansion products (benzazepinedione esters) 4a and c, and c) cyclization products (5d from the tert‐leucine derivative 2d). High diastereoselectivities (d.r. > 95:5) were observed for all reactions except the transformations of the 2‐aminobutyric acid derivative 2a. The absolute configuration of the α‐stereogenic center was retained during photolysis, as proven for the isode‐hydrovaline (type a product) 3b. PCC oxidation (to give 7b) and hydrogenation afforded 2b with an optical rotation comparable to the starting material. Treatment of 3b with an acid or a base led to epimerization (3b′) or isomerization of the C = C bond (6b), respectively. The diastereomeric dihydrobenz‐azepinedione esters 4a, b were formed with d.r. = 33:67 (cis: trans) and in 60% yield during photolysis of 2a. The isoleucine derivative 2e, however, was converted into the cis isomer 4a with high diastereoselectivity (d.r. >95:5), whereas the corresponding allo substrate 2f was only converted into the trans‐isomer 4b. Ethylene was extruded during irradiation of the latter substrates and during irradiation of the norvaline derivative 2c, whereas propene extrusion from the leucine derivative 2g led to the formation of the unsubstituted type b product 4c. The methionine derivative 1h was the only N‐phthaloylamino acid which did not show photodecarboxylation, instead two ζ‐hydrogen abstraction products were formed: the hydroxy acid 9h and the tetracyclic lactone 10h. The methionine ester 2h was only converted into the ring expansion products 11h, h′ presumably by a photo electron transfer step. The chronology of the double hydrogen transfer reaction (γ‐ followed by δ‐H abstraction, leading to type a products) was determined by using the deuterium labeled compound (±)[3–D1]‐2b.
Substituenteneffekte auf die Struktur von Spiropentan
Authors: Irngartinger Hermann , Gries Stefan , Klaus Philip , Gleiter Rolf
Published: July 2007

Substituent Effects on the Structure of Spiropentane

In order to investigate the influence of substituents on the bond lengths of the spiropentane framework, the molecular structures of the spiropentane derivates 1–7 have been determined by X‐ray analysis. The π acceptor substituents (CO, CO2R, Ph) shorten the distal bond of the substituted three‐membered ring by δ = ‐0.02 Å. The vicinal bonds are lengthened by δ/2. The π donor‐s̀ acceptor groups have the opposite effect [δ(Cl2) = 0.019, δ(F2) = 0.056 Å]. The influence of several substituents is additive. The longer peripheral bond [1.530(14) Å] is varied to the same degree as the shorter central bond [1.482(9) Å]. The second three‐membered ring of the spiropentane system is not affected. These results are explained qualitatively by considering the valence MO′s of a distorted spiropentane. Quantum chemical calculations using a 3–21 G basis set confirm this picture.
Substituenteneinflüsse auf die Struktur von 1‐Azaspiropent‐1‐en
Authors: Irngartinger Hermann , Gries Stefan
Published: July 2007

Substituent Effects on the Structure of 1‐Azaspiropent‐1‐ene

Low‐temperature (199 K) X‐ray structure analyses of the azaspiropentene 1 and its dimer 2 have been undertaken. The peripheral bonds of 1 (C–C 1.544, C=N 1.278 Å) are elongated because of steric strain and conjugation with the phenyl ring (for C=N). The distal bond (C–C 1.485 Å) in the three‐membered ring of 2 is shortened by the substituent effects of the N=C and C=N groups.
Verklammerte Tolane
Authors: Bauer Martin , Nieger Martin , Vögtle Fritz
Published: July 2007

The tolanophanes 1, 2 and 3 are prepared by Wittig cyclization reactions. The corresponding “stilbenophanes” 21 and 13 are also isolated. The X‐ray structure analysis of 1 revealed a bending of the acetylene triple bond by 11 degrees. Attempts to aim at the “superphane” 23 by reaction with transition metal complex catalysts were unsuccessful; reaction with phenyl‐carbene lead to the cyclopropenyl cation 22.
Synthesis of 1‐Substituted 1,2,3,4‐Tetrahydroisoquinolines from Enamino Ketones
Authors: Tietze Lutz F. , Schimpf Ralph , Wichmann Jürgen
Published: July 2007

The reaction of the N‐acylated enamino ketones 4a–d with trifluoroacetic acid, TMS triflate, or Lewis acids leads to the 6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinolines 5a–d in 84 to 94% yield. The enamino ketones 4f–i can only be cyclized with trifluoromethanesulfonic acid to the 1,2,3,4‐tetrahydroisoquinolines 5f–i in 75–84% yield. For the synthesis of 5e from the enamino ketone 4e carrying the benzyloxycarbonyl group TMS triflate is the best mediator (93%). The trichloromethylcarbonyl group in 5 can easily be transformed into a methoxycarbonyl group by treatment with K2CO3 in methanol to give 6 in 83–90% yield.
Darstellung und Photochemie eines (Anthrylvinyl)thiophenfulgids
Authors: Effenberger Franz , Wonner Johann
Published: July 2007

Preparation and Photochemistry of an Anthrylvinyl Thiophene Fulgide

The base‐catalyzed reaction of isopropylidenesuccinate 2 with phenylthienylpropenone 1a does not give a Stobbe condensation to 3a but results in an 1,4‐addition to 7 which under the basic conditions reacts further to 8 by an intramolecular condensation. The (anthrylvinyl)thiophene fulgide 4c is obtained, however, from 3‐glyoxyloyl‐2,5‐dimethylthiophene hydrate (11) via the 2H‐pyran 14: Wittig olefination of 14 with the phosphonium salt 16 leads to the diester 3c which easily is converted to Z,E‐4c. – Irradiation of Z,E‐4c gives a mixture of all four possible E,Z isomers of 4c and the ring‐closed valence tautomers Z‐ and E‐17. All isomers could be separated and characterized. Compound 18, formed irreversibly in a thermally‐induced reaction, is enriched during irradiation.
Photolyse von 3‐Methyl‐5,5‐diphenyl‐3,5‐dihydro‐4H‐1,2,3‐triazol‐4‐on
Authors: Quast Helmut , Hergenröther Thomas
Published: July 2007

Photolysis of 3‐Methyl‐5,5‐diphenyl‐3,5‐dihydro‐4H‐1,2,3‐triazol‐4‐one[1]

Irradiation (λ, ≥ 280 nm) of a degassed solution in deuterated benzene of the dihydro‐1,2,3‐triazolone 5 yields the dihydroindolone 7, the imine 9, and its photoreduction product 10, besides molecular nitrogen.
Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, LXXIX. Synthese eines Diphosphamanganacyclopentens durch Alkin–Insertion in die Mn–P–Bindung eines Diphosphamanganacyclopropans
Authors: Lindner Ekkehard , Darmuth Monika , Fawzi Riad , Steimann Manfred
Published: July 2007

Metal–Containing Heterocycles: Preparation, Properties and Reactions, LXXIX[1a]. – Synthesis of a Diphosphamangana–cyclopentene by Alkyne Insertion into the Mn–P Bond of a Diphosphamanganacyclopropane

Insertion of the alkyne ZCCZ with ZCO2Me into the Mn–P bond of the diphosphamanganacyclopropane results in the formation of the thermally and kinetically stable diphosphamanganacyclopentene (2). According to an X–ray structural analysis 2 crystallizes in the orthorhombic space group P212121 with Z  4.
Retro [1,4]‐Brook Rearrangements of Nonconjugated Secondary α‐Lithio Ethers: Proof of Stereospecificity and of Retention of Configuration at the Carbanion Center
Authors: Hoffmann Rolf , Brückner Reinhard
Published: July 2007

The syntheses of two pairs of diastereomeric γ‐(trialkylsilyloxy) α‐(tributylstannyl) ethers (syn‐ and anti‐6b, syn‐ and anti‐9) are described. Treatment of each of these compounds with nBuLi in THF at −78°C furnished α‐lithiated ethers which underwent retro [1,4]‐Brook rearrangements at that temperature within 15–30 min. After aqueous workup, the α‐silyl ethers syn‐14, anti‐14, syn‐11, and anti‐11, respectively, were isolated isomerically pure in 78–93% yield. Comparison of the stereochemistry of starting materials and products shows that these rearrangements proceed stereospecifically and with retention of configuration at the carbanion center. In a cross–over experiment under similar conditions, a 1:1 mixture of the (tributylstannyl) ethers syn‐9 and syn‐6b gave, via the intermediacy of a 1:1 mixture of the α‐lithiated ethers syn‐13 and syn‐10, the α‐silyl ethers syn‐11 and syn‐14 exclusively. They represent the outcome of intramolecular rearrangements rather than intermolecular processes.
Thermolyse von 1,2,3,4,6,7,8–Heptaazaspiro[4.4]nona–2,7–dienen, [3 + 2]‐Cycloaddukten von Aziden an 5–Alkyliden–4,5–dihydro–1H‐tetrazole
Authors: Quast Helmut , Balthasar Jürgen , Hergenröther Thomas , Regnat Dieter
Published: July 2007

Thermolysis of 1,2,3,4,6,7,8–Heptaazaspiro[4.4]nona–2,7–dienes, [3 + 2] Cycloadducts of Azides and 5–Alkylidene–4,5–dihydro–1H‐tetrazoles

On thermolysis of the title compounds at 20–150°C, three modes of ring cleavage are observed, viz. [3 + 2] cycloreversion of the triazole (path A) or the tetrazole ring (path B) to azide 2 and the corresponding dipolarophile, or extrusion of molecular nitrogen from the triazole ring with concomitant 1,2 shift of a nitrogen atom of afford an iminotetrahydrotetrazine 31 (path C). An equilibrium between [3 + 2] cycloaddition and cycloreversion (path A) is established starting from the heptaazaspiro[4.4]nonadienes 4. Irreversible [3 + 2] cycloreversion of the tetrazole ring (path B) is observed on thermolysis of 6, yielding azide 2 and iminodihydrotriazoles 7. Path A and B compete in the thermolysis of 6e affording, besides methyl azide (2a), 5c and 7e. Because path A is reversible, the former disappears again while the latter extrudes molecular nitrogen to yield the iminoaziridines (E)‐ and (Z)‐12 which decompose to the imine 13 and methyl isocyanide (14). Competition between path A and B is also observed on thermolysis of 15 and, probably, the diphenyl compound 21 as well. The latter affords a complex mixture comprising the iminodihydrotriazole 16, the iminoaziridines 18 and 23, the [2 + 1] cycloreversion products 14 and 19 of 18, and the 2–aminoindole 26 which is formed by isomerization of 18 and/or 23. None of the [3 + 2] cycloreversion reactions, but only extrusion of molecular nitrogen and formation of 31 (path C) are observed on thermolysis of the nitrophenyl spirocycles 29. The course of the thermolyses is mainly governed by the size and the electronic character of the substituent that stems from the azide used in the formation of the title compounds.
Organische Synthesen mit Übergangsmetall–Komplexen, 61[1] Pyridine und Pyridinium–Salze aus (β‐Aminovinyl)carben–Komplexen (MCr, W) und Alkinen über 4(1H)‐Pyridinyliden–Komplexe
Authors: Aumann Rudolf , Hinterding Peter
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 61[1]. – Pyridines and Pyridinium Salts from (β‐Aminovinyl)carbene Complexes (MCr, W) and Alkynes via 4(1H)‐Pyridinylidene Complexes

Pyridines and pyridinium salts were obtained in good yields by the condensation of (β‐aminovinyl)carbene complexes with alkynes. The reaction of [(Z)‐β‐(monoalkylamino)vinyl]carbene complexes [ 4‐(monoalkylamino)‐1–metalla–1,3–dienes)] LnMC(OEt)CHCRNHR1 (Z)‐6a–f (R, R1Ph, Me, iPr, nBu, CH2Ph, CH2OMe) with alkynes R2CCH 7a–c (R2  nBu, Ph, CH2OMe) involves the highly regioselective formation of 4(1H)‐pyridinylidene complexes . Protonation of 8 with HBF4 leads to pyridinium salts 13 by the regiospecific substitution of the metal moiety LnM by a proton. The reaction may conveniently be performed in a one–pot procedure. {[(Z)‐β‐(H2‐Amino)vinyl]carbene}chromium complexes, e.g. 14, react with alkynes to give pyridines, e.g. 15. The thermal decomposition of 6 yields enol ethers 11. A regiospecific formation of (E)‐11 is observed in the thermolysis of 6 in the presence of pyridine.
Organische Synthesen mit Übergangsmetall–Komplexen, 62. Erste Carbenkomplexe (MCr, W) mit Kohlenhydrat–Substituenten
Authors: Aumann Rudolf
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 62. – First Carbene Complexes (MCr, W) with Carbohydrate Substituents

The first examples of transition metal carbene complexes of carbohydrate derivatives are described: 1,2:5,6–Di‐O‐isopropyliden‐α‐D–glucofuranose (2a), 1,2:5,6–di‐O‐isopropylidene‐α‐D–allofuranose (2b), and 2,3:5,6–di‐O‐isopropyliden‐α‐D–mannofuranose (2c) add regiospecifically at C–3 of alkynylcarbene complexes LnMC(OEt)–CCPh 1 [LnMCr(CO)5 (a), W(CO)5 (b)] to give vinylcarbene complexes LnMC(OEt)–CHC(Ph)–O(sugar) (E/Z)‐3a–g in good to excellent yields. As a minor side reaction the alkynyl carbene complex (CO)5WC(OEt)–CCPh (1b) isomerises to give the 1,2–propadienylidene complex (CO)5WCCC(OEt)C6H5 (4b).
Synthesis of 9,10–Dihydro–9,10–propanoanthracen–12–ones Substituted at the Bridgehead
Authors: Martin H. , Hoffmann R. , Karama Usama
Published: July 2007

A variety of 9,10–dihydro–9,10–propanoanthracen–12–ones 1–11 has been prepared from anthracenes 15–23, α,α′‐dibromo ketones 12–14 and zinc/copper couple by using dioxane as solvent and ultrasonication at 15–20°C. 2,2,4,4–Tetrabromoacetone (12) afforded cycloadducts, in which the two bromine atoms at C–11 and C–13 are introduced stereoselectively cis and adopt a syndiaxial instead of a cis‐diequatorial position (5 examples). Even the cis‐configurated methyl groups in adducts 8, 9 and cis‐11 adopt syndiaxial positions preferentially.
Mehrfachbindungen zwischen Hauptgruppenelementen und übergangsmetallen, CVIII. Stöchiometrische und katalytische Oxidation elektronenarmer Olefine mit Osmiumtetraoxid: Eine neue Oxidationsmethode für Fluorolefine
Authors: Herrmann Wolfgang A. , Eder Stefan J.
Published: July 2007

Multiple Bonds between Atoms of Main Group Elements and Transition Metals, CVIII. — Stoichiometric and Catalytic Oxidation of Electron‐poor Olefins with Osmium Tetraoxide: A Novel Oxidation Method for Fluoroolefins

In contrast to current opinion, osmium tetraoxide reacts even with very electron‐poor olefins. For example, both partially and fully fluorinated osmate(VI) esters 2 are thus formed from fluoroolefins 1 by cycloaddition. Hydrolysis of the osmate(VI) esters leads to the corresponding 1,2‐diols 3 and, eventually, consecutive fluoroorganic products by HF elimination. A catalytic version of this route opens a new, general, and efficient entry to oxidation products in fluoroolefin chemistry. Tetrahalide ethylene derivatives of formula py2O2Os(OCX2CX2O) (X = Cl, F) split off oxalyl halide upon thermal treatment with the complexes py2O2OsX2 thus being formed in good yields.
Notizen / Notes [Li2(THF)4DAD] und [DAD — H][ZrCl5(THF)]: Neue Strukturvarianten phenylsubstituierter 1,4‐Diaza‐1,3‐dien‐Liganden
Authors: Scholz Joachim , Richter Bodo , Goddard Richard , Krüger Carl
Published: July 2007

[Li2(THF)4DAD] and [DAD — H][ZrCl5(THF)]: New Types of Phenyl‐;Substituted 1,4‐Diaza‐1,3‐diene Ligands

Two extreme situations in 1,4‐diaza‐1,3‐diene (DAD) chemistry are described. Reaction of phenyl‐substituted DAD 1a — c with lithium in the molecular ratio of 1:2 affords in high yield the extremely air‐sensitive complexes [Li2(THF)4DAD] (2a — c). The structure of 2b has been determined by X‐ray diffraction. Each of the Li+ ions is coordinated by the two terminal N atoms of the s‐cis‐configurated DAD dianion and by two molecules of THF. Protonation of ZrCl4 · DAD (3a) by HCl in THF gives the ionic complex [ZrCl5(THF)][DAD — H] (4), which contains a protonated [DAD — H]+ cation. The structure of the sterically crowded N = C — C = N skeleton of the [DAD — H]+ cation is not influenced by the positive charge and adopts the unusual Z‐gauche‐Z conformation.
Reaktive E = C(p‐p)π‐Systeme, XXXIII. Side‐on‐Koordination des Phosphaalkins P ≡ C — N(iPr)2 im 16e‐Nickel(0)‐Komplex Ni(CO)PCy3[PCN(iPr)2]
Authors: Grobe Joseph , Van Duc Le , Hegemann Marianne , Krebs Bernt , Läge Mechtild
Published: July 2007

Reactive E = C(p‐p)π Systems, XXXIII. — Side‐on Coordination of the Phosphaalkyne P ≡ C — N(iPr)2 in the 16e Nickel(0) Complex Ni(CO)PCy3[PCN(iPr)2]

The reaction of (diisopropylamino)phosphaethyne P ≡ C — N(iPr)2 with the nickel complex [Ni(CO)3PCy3] – in contrast to the analogous reactions with Ni(CO)4 or Ni(CO)3PR3 (R = Me, Ph) – leads to the novel 16e nickel(0) system [Ni{η2‐P ≡ C — N(iPr2)}(CO)PCy3] with a planar geometry of all skeleton atoms besides the methyl and cyclohexyl groups. Side‐on coordination of the P ≡ C triple bond results in an increase of the PC distance to 1.665 Ȧ typical for phosphaalkenes.
Struktur eines Silaethen‐Aminaddukts
Authors: Wiberg Nils , Joo Kwang‐;Suk , Polborn Kurt
Published: July 2007

Structure of a Silaethene Amine Adduct

The reaction of Me2SiBr‐CBr(SiMe2Ph)2 with PhLi in the presence of NEtMe2 leads to EtMe2N…︁SiMe2…︁C(SiMe2Ph)2 (3). NEtMe2 is coordinated to the central silicon. The SiN distance is comparably long (1.988 Ȧ). The bond distance between the central (distorted tetrahedra) silicon and the central (planar) carbon (1.761 Ȧ) is longer than the SiC distances in silaethenes (1.70 Ȧ) and shorter than the SiC distances in silaethanes (1.87 Ȧ). From a comparison of structures of D…︁SiMe2 \documentclass{article}\pagestyle{empty}\begin{document}$ \underline \cdots $\end{document} C(SiR3)2 it is concluded that increasing Lewis basicity of D (THF < NEtMe2 < F¯) leads to a SiC bond lengthening and to more regularity in the geometry of the distorted tetrahedral silicon.
Zur Tautomerie von 5,5‐Diphenyldihydro‐4H‐1,2,3‐triazol‐4‐on und 5‐Amino‐4,4‐diphenyl‐4H‐1,2,3‐triazolen
Authors: Quast Helmut , Hergenrüther Thomas , Banert Klaus , Peters Eva‐;Marie , Peters Karl , Schnering Hans Georg Von
Published: July 2007

Tautomerism of 5,5‐Diphenyldihydro‐4H‐1,2,3‐triazol‐4‐one and 5‐Amino‐4,4‐diphenyl‐4H‐1,2,3‐triazoles

Methylation of the 5‐amino‐4H‐1,2,3‐triazole 5 affords the N‐methyl‐ (12) and the N,N‐dimethylaminotriazole 13. X‐ray diffraction analyses show that the tautomer 5b exists in the crystal and that 5b and 13 possess similar structures and atomic distances. Both compounds exhibit restricted rotation of the amino groups in solution. The comparison of UV, carbon‐13 and nitrogen‐15 spectra of the tautomeric triazoles 2 and 5 with those of the N‐methyl compounds 3 and 13 demonstrates that the tautomers 2a and 5b are strongly favoured also in solution.
3‐Azabicyclische Ketone durch Reaktionen von 1,3‐Diethoxy‐2‐azapropenylium‐Salzen mit Enaminen cyclischer Ketone
Authors: Schleimer Richard , Hornig Knut , Würthwein Ernst‐;Ulrich , Müller Manfred H.
Published: July 2007

3‐Azabicyclic Ketones from 1,3‐Dialkoxy‐2‐azapropenylium Salts and Enamines of Cyclic Ketones

1,3‐Diethoxy‐2‐azapropenylium salts 1 are powerful biselectrophiles and react diastereoselectively with enamines of five‐membered ring ketones 2 to yield novel 3‐azabicyclo[3.2.1]oct‐2‐en‐8‐one 5 after hydrolysis of the intermediate iminium salts 3, 4. Some of the iminium salts 3 can be hydrolyzed further to provide the diketo imines 6. With enamines of six‐membered ring ketones 7 the 3‐azabicyclo[3.3.1]non‐2‐en‐9‐ones 10, 11 are obtained after hydrolytic workup. Mixtures of diastereomers 10/11 are found in the case of 7a, b, whereas with 7g — j the endo‐phenyl derivatives 10 are formed exclusively. With the unsymmetrical enamine 7b only one regioisomer is observed. The decalone enamine 12 reacts with 1a to yield the tricyclic iminium salt 13. — The configuration of the bicyclic products has been determined by using NMR spectroscopic techniques (COSY, polarisation transfer by long range couplings); an X‐;Ray analysis of compound 10a is used as basis for the NMR assignments. General rules for the determination of the stereochemistry of these azabicyclic systems by 1H‐NMR shift arguments are derived.
Highly Unsaturated Oligomeric Hydrocarbons: α‐(Phenylethynyl)‐ω‐phenylpoly[1,2‐phenylene(2,1‐ethynediyl)]
Authors: Grubbs Robert H. , Kratz Detlef
Published: July 2007

A new set of conjugated oligomers C6H5C…︁C–(1,2‐C6H4C…︁C)n – C6H5 (10; n = 3–7) comprised of acetylene and phenyl units linked together at the 1,2 positions of the aromatic ring is introduced. The facile synthesis of these compounds is achieved through the Pd‐mediated coupling reaction of diiodo‐ and dibromobenzene with the appropriate ethynyl component. Spectroscopic data of the new compounds are discussed in light of electronic conjugation of the extended π system. Thermolysis of oligomers 10 indicates that rearrangement of the triple bonds occurs to form higher conjugated oligo(acenes). The topology of two members (10; n = 2, 3) is confirmed by X‐ray analysis and reveals a propensity for intramolecular π‐stacking of the phenyl rings leading to a helical arrangement.
Trimethylsilylcyanid als Umpolungsreagens, XXI. Regioselektivität der Reaktionen von substituierten α‐Siloxy‐α‐cyanallyl‐Anionen mit α,β‐ungesättigten Ketonen
Authors: Hünig Siegfried , Schäfer Matthias , Schweeberg Walter
Published: July 2007

Trimethylsilyl Cyanide — A Reagent for Umpolung, XXI. — Regioselectivity of the Reaction between Substituted α‐Siloxy‐α‐cyanoallylic Anions and α,β‐Unsaturated Ketones

Ambident allylic anions A and ambident α,β‐unsaturated ketones B combine to the four isomeric products D — G (Scheme 1). Systematic variation of substituents in A, obtained by deprotonation of 1a — c with LDA, and in B (→ 2a — d) as well as variation of the reaction medium and temperature reveals the following results: In diethyl ether (DE) at –78°C the kinetic products 3 (1,2/α) prevail, except with 2d. On warming rearrangement occurs to the thermodynamic products 4 (1,4/α) and/or 6 (1,4/γ) depending strongly on the substituents in both 1 and 2 (Tables 1 – 3). Adducts 6 (1,4/γ) are supposed to be formed by anionic oxy‐Cope rearrangement, since the isolated products 4 rearrange thermally to 6 in rates which reflect the yields of 6 isolated (Table 7). Substitution of DE by THF (and addition of HMPT) strongly favours adducts 4 and 6 (Table 4). With 1a + 2c a series of Lewis acids was also tested (Table 5). With MgBr2 the so far missing 1,2/γ product 5ac becomes the major one. In contrast, ClTi(NEt2)3 preserves the kinetic 1,2/α product 3ac totally even at 0°C. This behaviour is found also with other combinations of 1 + 2 (Table 6). By proper choice of the conditions the reaction between a given pair of 1 and 2 can be steered to produce one of the four possible adducts predominantly.
Sterically Congested Molecules, 6. Lone Electron Pair Donor Quality of the Imino Function: Increased Front Strain and Electronic Substituent Effects on Sterically Accelerated Nitrogen Inversion in Iminocyclopentanes
Authors: Knorr Rudolf , Hoang Thi Phung , Mehlstäubl Johann , Hintermeyer‐;Hilpert Monika , Lüdemann Hans‐;Dietrich , Lang Elmar , Sextl Gerhard , Rattay Wilfried , Bührer Petra
Published: July 2007

The p‐substituents of 2,6‐dimethyl‐N‐(2,2,5,5‐tetramethylcyclopentylidene)anilines are modified without interfering reactions at the CN double bond. The resultant series (5 – 8, 10 – 19) shows a strong (ca. —4.7 kcal/mol) steric acceleration of (E/Z) diastereotopomerization by front strain along the CN double bond but also the usual electronic substituent dependence, characterized by a Hammett s̀p– correlation (Q = +2.7). Conversely, the substituent constant for lithium at the p‐position of 7 may be estimated. The volume of activation is 1.5(8) cm3 mol–1 for 5. The π donor quality of the imino group corresponds to ca. 55 (±8)% of Pπ character as evaluated by spectral (13C NMR of 5 and 13, IR of 13) and reactivity data (of 13).
Alkylierungsreaktionen an 4,5‐Bis(trifluormethyl)‐1,3‐dithiol‐2‐thion — Erste Röntgenstrukturanalyse eines 2‐Alkylthio‐1,3‐dithiolium‐Salzes
Authors: Frasch Markus , Mono Susanne , Pritzkow Hans , Sundermeyer Wolfgang
Published: July 2007

Alkylation Reactions of 4,5‐Bis(trifluoromethyl)‐1,3‐dithiole‐2‐thione — A First X‐ray Structure Determination of a 2‐Alkylthio‐1,3‐dithiolium Salt

The 2‐alkylthio‐1,3‐dithiolium salts 2a — e have been prepared by reaction of 4,5‐bis(trifluoromethyl)‐1,3‐dithiole‐2‐thione (1) with strong alkylating agents like alkyl perfluorobutanesulfonates or Meerwein salts. The first X‐ray structure determination shows a localized double bond in the ring system combined with a trithiocarbenium ion in 2e.
Organosubstituierte 1,2‐Diborylalkene — Herstellung und Photoisomerisierung
Authors: Köster Roland , Seidel Günter , Wrackmeyer Bernd
Published: July 2007

Substituted 1,2‐Diborylalkenes — Preparation and Photoisomerization

The organo(halo)substituted cis‐1,2‐diborylalkenes cis1‐R2BC(R)C(Et)BEt2 (Z)‐1 to (Z)‐14 are prepared [route I from Na[R3BCCR] and ClBR2; route II from cis1‐R3SnC(R)C(Et)BEt2 and RnBHal3+n′ n0–2; (Z)‐11 (route III): cis1‐ClB(Ph)CHC(Et)BEt2 and Me3SiOMe]. Their 11B‐and 13C‐NMR data show the degree of pz(B)/(CC) π overlap and are compared with the corresponding data of the monoboryl alkenes [(Z)‐15, 16, (Z)‐17, (Z)‐23, (Z)‐24, (Z)‐26], the cis‐2‐boryl‐1‐silylalkenes [(E)‐18, (E)‐19, (E)‐27, (E)‐28], and the cis‐2‐boryl‐1‐stannylalkenes [(E)‐20 to (E)‐22]. — Compounds (Z)‐3, (Z)‐4, (Z)‐9, (E)‐18, and (E)‐19 with one or two nearly coplanar pz(B) and pz(CC) groups (pl1‐R2B) are isomerized by UV irradiation to their equilibria with the corresponding trans isomers (E)‐3, (E)‐4, (E)‐9, (Z)‐18, and (Z)‐19, resp., with one or two nearly orthogonal pz(B) and pz(CC) groups (or1‐R2B). Irradiation of (Z)‐9 gives the isomer pair (Z/E)1‐iso‐9 by a Ph/Et exchange between the two boron atoms.
Kristallstruktur, Festkörperpolymerisation und Ionenleitung in Alkalisalzen ungesättigter Carbonsäuren, 3. Untersuchungen an Lithiumcrotonat, Dilithiumfumarat‐tetrahydrat und Dilithiummaleat‐monohydrat
Authors: Beck Horst P. , Trübenbach Peter
Published: July 2007

Crystal Structure, Solid‐State Polymerization, and Ionic Conductivity of Alkali Salts of Unsaturated Carboxylic Acids, 3[1]. — Investigations on Lithium Crotonate, Dilithium Fumarate‐Tetrahydrate, and Dilithium Maleate Monohydrate

The structures of lithium crotonate (1), dilithium fumarate tetrahydrate (2), and dilithium maleate monohydrate (3) have been determined by single‐crystal X‐ray diffraction and are discussed in detail in view of the possibility to realize a topochemical polymerization. Compounds 1 and 3 can be polymerized thermally, however this results in a complete breakdown of the crystal structure. Impedance measurements show a weak ionic conductivity in the case of 2. The other compounds and the products of thermal polymerization are isolators with a mean Dkr′ of about 4.0.
Synthesis and Structure of (Hydridosilyl)hydrazines
Authors: Mitzel Norbert W. , Bissinger Peter , Schmidbaur Hubert
Published: July 2007

A series of (hydridosilyl)hydrazines 1 – 12 has been prepared from the corresponding chloro‐or bromosilanes and hydrazines in the presence of triethylamine as an auxiliary base. Methylsilyl (MeH2Si‐), dimethylsilyl (Me2HSi‐), and phenylsilyl (PhH2Si‐) groups have been introduced as substituents. NMR spectra (1H, 13C, 15N, 29Si) have been measured and used to determine the rotation barrier about the N — N bond in (PhH2Si)(Me2HSi)N — N(SiHMe2) (9), which has been found to be 75 kJmol–1. The crystal structure of (PhH2Si)2N — N(SiH2Ph2 (7) features each of the two NNSi2 groups as nearly planar, but with a dihedral angle close to orthogonal. Such a structure is also implied for 9 on the basis of the NMR spectra.
Reaktivität von Phosphor‐Ylid‐Derivaten auf Ru31‐Clustern: Umwandlungen durch Alkin‐Insertion
Authors: Heineke Daniel , Vahrenkamp Heinrich
Published: July 2007

Reactivity of Derivatives of Phosphorus Ylides on Ru3 Clusters: Interconversions due to Alkyne Insertion

The Ru3 clusters with triply bridging organic ligands derived from phosphorus ylides undergo interconversions by insertion of alkynes. The phosphoniomethylidyne‐bridged cluster H2Ru3(CO)9(μ31‐C — PPh3) (1) inserts alkynes either into one Ru — H bond (HCCSiMe3, EtCCEt) forming μ21‐vinyl‐Ru3 complexes or into the Ru3‐μ31‐C unit (HCCSiMe3, PhCCPh) converting it into a μ31‐allyl ligand, e.g. in Ru3(CO)8(PPh3)(μ31‐Ph3P — CCHCSiMe3) (6). HCCPh induces fragmentation of 1. The phosphonio enolate‐bridged clusters HRu3(CO)9‐(μ31‐Ph3P — CH — CO) (2a) and HRu3(CO)8(PPh3)(μ31‐Ph3P — CH — CO) (2b) insert alkynes (HCCPh, PhCCPh, HCCSiMe3, EtCCEt) into the Ru — H bond to form μ21‐vinyl‐bridged derivatives, e.g. Ru3(CO)8(μ31‐Ph3P — CH — CO)(μ21‐RCCHR′) (9). In addition, the alkyne reactions of 2a induce cluster opening with concomitant CO and alkyne incorporation into the organic ligand and formation of an oxaruthenol‐derived trinuclear complex 11, as proved by an X‐ray structure determination of the PhCCPh product 11b. For the cluster H2Ru3(CO)7(PPh3)(μ31‐C6H4Ph2P — C(O)Me) (3) containing an ortho1‐metalated phosphonio ketone ligand, only alkyne insertion into one or two Ru — H units is observed.
Metal Complexes in Inorganic Matrices, 10. Preparation of Phosphanyl‐Spacer‐Substituted Metal Alkoxides (RO)3E‐X‐PPh2 (ETi, Zr; XSpacer)
Authors: Buhler Hermann , Schubert Ulrich
Published: July 2007

The reaction of HPPh2 with (PrO)3E(O2CCHCH2) (ETi, Zr), formed in situ by the reaction of E(OPr)4 with acrylic acid, gives the phosphanylpropionate derivatives (PrO)31‐E(O2CCH2CH2PPh2). The phosphanylacetate derivative (PrO)3Zr(O2CCH2PPh2) was obtained by treatment of (PrO)31‐Zr(O2CCH2Cl) with LiPPh2. (BuO)3Ti(π1‐C5H4[CH2]2PPh2) was prepared by the reaction of Li(C5H4[CH2]2PPh2) with (BuO)31‐TiCl.
Organische Synthesen mit Übergangsmetall‐Komplexen, 63. (β1‐Aminovinyl)carben‐Komplexe und (Alkinyl)aminocarben‐Komplexe von Chrom und Wolfram. — Stereochemie und Isomerisierung
Authors: Aumann Rudolf , Hinterding Peter
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 63[1]. — (β1‐Aminovinyl)carbene complexes and (Alkinyl)aminocarbene Complexes of Chromium and Tungsten. — Stereochemistry and Isomerization

(Alkinyl)alkoxycarbene complexes LnMC(OEt)–CCR 3 [LnMCr(CO)5, W(CO)5; RPh, nBu, SiMe3] react with primary amines H2NR1 4 (R1Me, iPr, allyl, CH2Ph, CHMePh) to give (β1‐aminovinyl)carbene complexes LnMC(OEt)–CHCR‐NHR1 (Z)‐5 (by a Michael‐type 3‐addition) together with (alkinyl)aminocarbene complexes anti‐6 (by a 1‐aminolysis). The product ratio (Z)‐5/anti‐6 is strongly influenced by the reaction temperature: at 20°C (Z)‐5 is obtained as the main product, while at –78°C mainly anti‐6 is formed. Both reactions are stereospecifical; they yield 5 in the (Z), and 6 in the anti configuration only. An anti/syn isomerization is achieved by acidic treatment of anti‐6i. The (alkinyl)aminocarbene complex 6a adds EtOH/EtO– albeit much slower than the (alkinyl)alkoxycarbene complex 3a. A NH21‐Enamino carbene complexes (CO)5CrC(OEt)–CHC(NH2)Ph [(Z)‐8a] is obtained on addition of ammonia to 3a at 90°C.
The Stereochemistry of the Trinaphthyl‐Terrylene Conversion
Authors: Anton Ute , Adam Martin , Wagner Manfred , Qi‐Lin Zhou , Müllen Klaus
Published: July 2007

Alkylated terrylenes can be synthesized by a twofold cyclization of an appropriately substituted trinaphthyl[1, 11]. In this paper, we consider a special case. The alkyl substitution in the starting material 1 strongly affects the interplanar angle between the naphthalene moieties. After cyclization, the substituents are positioned in the sterically crowded bay region of the title structure 2. The influence of the steric strain on the reactivity of 1 and on the stability of the resulting hydrocarbon 2 is investigated. Special emphasis is placed on the crystal structures of 1 and 2.
[3 + 2] Cycloadditions with Azirines under the Conditions of Photoinduced Electron Transfer: A New Method for the Synthesis of Imidazoles and Heterophanes
Authors: Müller Felix , Mattay Jochen
Published: July 2007

With the opening of azirine rings under the conditions of photoinduced electron transfer a new synthon for the synthesis of heterocycles is available. The formed 2‐azaallenyl radical cation readily reacts with imines to form N1‐substituted imidazoles in reasonable yields. The synthesis of pyrrolophanes and imidazolophanes from bicyclic azirines is possible as well. With oligocyclic azirines complex heteroaromatic systems and even a porphyrin system can be built up.
Silaheterocyclen, XXII. Diels‐Alder‐Reaktionen von Dichlor(neopentyl)silaethen mit Furanen und Umlagerung der erhaltenen Bicyclen zu monocyclischen Si – O‐Siebenring‐Verbindungen
Authors: Auner Norbert , Wolff Astrid
Published: July 2007

Sila Heterocycles, XXII[1]. – Diels‐Alder Reactions of Dichloro(neopentyl)silaethene with Furans and Rearrangement of the Resulting Bicycles into Monocyclic Si – O Seven‐Membered Ring compounds

The reaction of trichloro(vinyl)silane (1) and LitBu (2) initially leads to the α1‐lithio adduct Cl3SiCH(Li)CH2tBu (3) which can be trapped by trimethylsilyl triflate yielding the C1‐silylated product [Cl3SiCH(SiMe3)CH2tBu (5)]. 1,2‐LiCl elimination from 3 gives dichloro(neopentyl)silaethene [Cl2SiCHCH2tBu (4)] as intermediate. This can be established by insertion of 4 into the Si – O bond of Me3SiOMe to Cl2Si(OMe)CH(SiMe3)CH2tBu (6). 4 is a dienophile of high activity and reacts with the furans 7 – 9 to give the [4 + 2] cycloaddition compounds 10 – 12. These Diels‐Alder products are thermally unstable and decompose slowly at room temperature into the starting furans and tetrachlorodisilacyclobutane (15). Under thermolysis conditions (3 d/17°C) they rearrange into the monocyclic Si – O seven‐membered ring compounds 16 – 18. A mechanism for the 7‐Oxa‐2‐silabicyclo[2.2.1]hex‐5‐en → 1‐Oxa‐2‐silacyclohepta‐4,6‐diene rearrangement is proposed.
Synthesis and Molecular Structure of Heterocycles Containing two Phosphorus(V) Centers Bridged by Two‐Coordinate Phosphorus and Arsenic
Authors: Gamper Siegfried F. , Schmidbaur Hubert
Published: July 2007

1,1‐Bis[(diphenylphosphanyl)methyl]ethene (3) reacts with PCl3 or AsCl3 in the presence of SnCl2 as a reducing agent to form cationic heterocycles in which the two newly generated phosphonium centers are bridged by two‐coordinate, negatively charged phosphorus (4a) or arsenic (4b) centers. Hexachlorostannate(IV) dianions function as counterions to these heterocycles, in which the exocyclic methylene group is retained. By treatment of 4a with a base a rearrangement is induced which includes a proton migration from an endo‐to the exocyclic CH2 group to give 5‐methyl‐1,1,3,3‐tetraphenyl‐1λ5,2λ3,3λ51‐triphosphinine (5), a novel 1,2,3‐triphosphabenzene species. The reaction of the arsenic compound 4b with base did not yield the corresponding arsa‐diphosphabenzene, but gave only decomposition products. Compound 4b · 0.5 CH3CN has been studied by X‐ray crystallography. The six‐membered heterocycle shows a chair conformation with an arsenic atom solely coordinated by two phosphorus atoms at roughly equal distances with a sharp angle P – As – P of only 93.0(1)°.
Übergangsmetall‐Stannyl‐Komplexe, 7. Darstellung von Carben‐Komplexen (π1‐Aromat)(CO)2CrCR2 durch Umsetzung der anionischen Stannyl‐Komplexe [(π1‐Aromat)(CO)2CrSnPh3]– mit R2CX2 oder [R2CX]Y
Authors: Schubert Jürgen , Mock Stefan , Schubert Ulrich
Published: July 2007

Transition Metal Stannyl Complexes, 7[1]. – Preparation of Carbene Complexes (π1‐Arene)(CO)2CrCR2 by the Reaction of the Anionic Stannyl Complexes [(π1‐Arene)(CO)2CrSnPh3]– with R2CX2 or [R2CX]Y

Carbene complexes (π1‐arene)(CO)2CrCR2 are formed in substitution/elimination reactions from the anionic stannyl complexes K[(π1‐arene)(CO)2CrSnPh3] [π1‐areneC6H6 (1a), 1,3,5‐Me3C6H3 (1b), 1,2,4,5‐Me4C6H2 (1c)] C6Me6 (1d) and organic dihalides R2CX2 containing activated C – X bonds or ionic halides [R2CX]Y. Bis(stannyl) complexes (π1‐arene)(CO)2Cr(SnPh3)2 (3) and hydrido(stannyl)complexes (π1‐arene)(CO)2Cr(H)SnPh3 are formed as byproducts due to the reaction of the eliminated Ph3SnCl with the anionic starting complexes or electron transfer reactions, respectively. The portion and ratio of the byproducts is largely influenced by the steric properties of both the (π1‐arene)(CO)2Cr fragment and the organic halide. Pyridinylidene complexes 2) are only obtained from 2‐chloro‐N1‐methylpyridinium tetrafluoroborat with 1a – c, but not with 1d. With the sterically less demanding halides [R2NC(H)Cl]Cl [NR2NMe2, (n3, 4)] or 3,3‐dichloro‐1,2‐diphenylcyclopropene the carbene complexes (π1‐arene)(CO)2CrC(H)NR2 or are obtained with all employed π1‐arene ligands.
Über die‐Synthese und Molekülstruktur von CH3M(SiH3)3 (MSi, Ge)
Authors: Lobreyer Thomas , Oeler Johannes , Sundermeyer Wolfgang , Oberhammer Heinz
Published: July 2007

Synthesis and Molecular Structure of CH3M(SiH3)3 (MSi, Ge)

A solution of 2‐isotetrasilanylsodium (1a) was obtained in good yield from silane and sodium under special conditions. Methylation of 1a with methyl p1‐toluenesulfonate yields 2‐methylisotetrasilane (1b). The corresponding methyltrisilylgermane (2b) was synthesized via (K, Cs)Ge(SiH3)3 (2a) resulting from the reaction of cesium trichlorogermanide with KSiH3 followed by methylation. The molecular structures of 1a and 1b were determined by electron diffraction analyses.
Vinylidene Transition Metal Complexes, XXII[1]. – Alkyne, Alkynyl(hydrido)1‐, Vinylidene‐, and Vinylvinylidene Complexes of Rhodium from OH‐, NH2‐, and Cl‐Functionalized Alkynes
Authors: Werner Helmut , Rappert Thomas
Published: July 2007

The reaction of [RhCl(PiPr3)2]n with γ1‐functionalized 1‐alkynes HCC‐CRR′X (XOH, OMe, Cl, NH2) at room temperature leads to the formation of either alkyne‐, alkynyl(hydrido)1‐, or vinylidenerhodium complexes. The alkyne and alkynyl‐(hydrido) derivatives rearrange thermally or in the presence of deactivated Al2O3 to the isomeric vinylidenerhodium compounds in almost quantitative yield. On treatment of the γ1‐functionalized vinylidenerhodium complexes trans‐[RhCl(CCH‐CRR′X)(PiPr3)2] with Al2O3 or traces of acids, elimination of HX occurs and (for RH, CH3; R′CH3; XOH, Cl, NH2) the (vinylvinylidene)rhodium compounds trans‐[RhCl(CCH‐CRCH2)(PiPr3)2] are formed. In contrast, the reaction of trans‐[RhCl(CCHCPh2OH)(PiPr3)2] with either Al2O3 or acid gives the allenylidene complex trans‐[RhCl(CCCPh2)(PiPr3)2]. The 1‐hexyne derivatives HCC[CH2]3CH2X (XOH, Cl) react with [RhCl(PiPr3)2]n to give alkyne‐, alkynyl(hydrido)1‐, and vinylidenerhodium compounds; attempts to form the cyclic vinylidene complex trans‐ by HX elimination from trans‐[RhCl(CCCH[CH2]3CH2X)(PiPr3)2] (XOH, Cl) failed. The half‐sandwich‐type (vinylvinylidene)rhodium compounds [C5H5Rh(CCH‐CRCH2)(PiPr3)] (RH, Me) are obtained from [RhH(CC‐CRCH2)Cl(py)(PiPr3)2] and NaC5H5.
Synthesewege zu (μ1‐HO)Zn21‐Komplexen
Authors: Alsfasser Ralf , Vahrenkamp Heinrich
Published: July 2007

Synthetic Pathways for (μ1‐HO)Zn2 Complexes

The reactions of the 3‐substituted kalium hydrotris(pyrazolyl)1‐borates 1c, d (Rtert1‐butyl, anisyl) with Zn(ClO4)2 · 6 H2O produce the dinuclear μ1‐hydroxo complexes [L3Zn – O(H) – ZnL3](ClO4)3 (2a, b; L5‐tert1‐butylpyrazole, 5‐anisylpyrazole), due to hydrolytic cleavage of the B – N bonds. These and similar complexes (2c, d;5‐tert1‐butyl‐3‐methylpyrazole, 5‐phenylpyrazole) are also accessible directly from Zn(ClO4)2 · 6 H2O, the substituted pyrazole, and KOH, and in one case (2b; L5‐anisylpyrazole) by hydrolytic cleavage of [HB(3‐anisylpyrazolyl)3ZnEt] with perchloric acid. With other pyrazole and imidazole ligands, the Zn(ClO4)2/L/KOH reaction produces the simple complexes [ZnL6](ClO4)2 (3a, b; Lpyrazole, 3‐methyl‐5‐phenylpyrazole) and [ZnL4](ClO4)2 (4; L2‐methylimidazole). The crystal structures of 2a and 4, each containing tetrahedrally coordinated zinc atoms, have been determined.
(Bicyclo[3.2.0]hepta‐1,3‐dienyl)cobalt(I) Complexes
Authors: Angermund Klaus P. , Betz Peter , Butenschön Holger
Published: July 2007

Three isomeric bicyclo[3.2.0]heptadienes 1 – 3 are compared by semiempirical calculations. Experimental attempts directed to the synthesis of derivatives of 1 are described. The synthesis, properties and some reactions of (η51‐bicyclo[3.2.0]hepta‐1,3‐dienyl)(η41‐cycloocta‐1,5‐diene)cobalt(I) (22), including an X‐ray crystal structure determination of the reaction product with diphenylethyne, the tetraphenylcyclobutadiene complex 30, are presented.
Enzym‐katalysierte Reaktionen, 15. Darstellung von (R)1‐2‐(Sulfonyloxy)nitrilen und ihre Reaktionen mit Acetaten — Konfigurationsumkehr optisch aktiver Cyanhydrine[2]
Authors: Effenberger Franz , Stelzer Uwe
Published: July 2007

Enzyme‐Catalyzed Reactions, 15[1]. – Preparation of (R)1‐2‐(Sulfonyloxy)nitriles and Their Reactions with Acetates – Inversion of the Configuration of Optically Active Cyanohydrins

2‐(Sulfonyloxy)nitriles (R)‐6, 7, 8 are obtained in high optical purity from the respective cyanohydrins (R)‐2 by sulfonylation with methanesulfonyl chloride (3), toluenesulfonyl chloride (4), and trifluoromethanesulfonic anhydride (5), respectively. In contrast to the aliphatic (sulfonyloxy)nitriles (R)‐6, 7, 8a – e, the benzylic‐type mandelic acid derivatives (R)‐7,8í are unstable at higher temperature. The 2‐(sulfonyloxy)nitriles (R)1‐ 6, 7, 8a – e react at room temperature with alkali acetates in a typical SN2 manner to give the cyanohydrin acetates (S)‐9 in high optical purity. Under these reaction conditions, however, the mandelic‐type compounds (R)‐7, 8í partly racemize and decompose. By hydrolysis of the acetates (S)‐9, (S)1‐cyanohydrins (S)‐2 of aliphatic aldehydes are easily available.
Photoinduced Electron Transfer in Porphyrin‐Quinone Cyclophanes, 8 Conformational Mobility and Crystal Structures of Porphyrin‐Quinone Cyclophanes
Authors: Krieger Claus , Dernbach Matthias , Voit Guido , Carell Thomas , Staab Heinz A.
Published: July 2007

In order to correlate photoinduced electron‐transfer in porphyrin‐quinone cyclophanes to specific molecular conformations, the internal mobility of single‐and double‐bridged porphyrin‐quinone cyclophanes was studied by low‐temperature 1H‐NMR measurements. The dynamic processes observed are discussed in terms of N‐H/N tautomerisation, of the rotation of the rings in the bridges, and of a specific “swinging bridge” process back and forth between two equivalent unsymmetrical conformations with a tilted orientation of the porphyrin and quinone ring planes. For comparison with the conformational situation in solution the results of X‐ray structure analyses of 3(XOMe) and 6, as representative examples of single‐bridged quinone‐porphyrin cyclophanes, and of the corresponding tetramethoxybenzene‐bridged octamethylporphyrin cyclophane 4(XOMe) are reported and discussed. In contrast to the previously solved crystal structure of the quinone‐porphyrin‐quinone cyclophane 1(XH), all three X‐ray structure analyses of the single‐bridged porphyrin cyclophanes proved the existence of unsymmetrical, tilted‐plane structures similar to those discussed as the stable conformations in the “swinging bridge” process.