bluuebunny/crossref_metadata_2025 huggingface dataset:
Adamantan als Baustein neuer Araliphane Synthese, Spektroskopie und Kristallstrukturen
Authors: Dohm Joachim , Vögtle Fritz , Nieger Martin , Rissanen Kari
Published: July 2007

Adamantane as a Building Block of New Araliphanes – Synthesis, Spectroscopy, and Crystal Structures

Exchange of benzene units for aliphatic building blocks in cyclophanes leads to new molecules of the “araliphane” type. With adamantane the araliphanes 2 – 4 are synthesized. Their stereochemical behavior as shown by NMR studies and X‐ray crystallographic analyses differs significantly from that of their aromatic counterparts. The signals of the intraannular adamantane hydrogens are strongly shifted upfield up to δ=– 2.18 (in 2). 4 is obtained as a racemic mixture of enantiomers (in the crystalline state) and shows a boat‐like deformation of the benzene moiety.
Synthese mittlerer und großer Ringe, XXVIII. Die Rutheniumtetroxid‐Oxidation von 3,6‐Alkano‐4,5‐oligomethylenoxepinen Ein neuer Weg zu makrocyclischen Di‐, Tri‐ und Tetraketonen
Authors: Tochtermann Werner , Dibbern Regine , Haase Margret , Bruhn Thomas , Wolff Christian
Published: July 2007

Synthesis of Medium and Large Rings, XXVIII. – The Ruthenium Tetroxide Oxidation of 3,6‐Alkano‐4,5‐oligomethyleneoxepines – A New Approach to Macrocyclic Di‐, Tri‐, and Tetraketones

The oxepines 3, 7, and 9 are oxidized by means of ruthenium tetroxide to give various types of macrocyclic ketones such as 4, 8 and 10. The diketones 12 can be synthesized by ether cleavage of 9a to give 11a and subsequent oxidation of 11b and 11d to the monocyclic compounds 12a and 12b.
Sterische Behinderung der Isocyanid‐Cyanid‐Umlagerung in einer Brückenkopfposition
Authors: Pakusch Joachim , Rüchardt Christoph
Published: July 2007

Steric Hindrance of the Isocyanide‐Cyanide Rearrangement in a Bridgehead Position

The activation barrier of the isocyanide‐cyanide rearrangement of 13‐isocyano‐1,4,5,8,9,12‐hexamethyltriptycene (5) is the highest of all known isocyanides. The special position of this compound can be explained by a strong increase of strain enthalpy during the isomerization. This is due to the cage‐like inclusion of the isocyano group in the bridgehead position by the methyl groups in the positions 1, 8, and 9.
Metal Complexes with Tetrapyrrole Ligands, LVIII. Zirconium(IV) and Hafnium(IV) Bisporphyrinate Double Deckers: Synthesis, Spectra, Redox Potentials, and Structure
Authors: Buchler Johann W. , Cian André De , Fischer Jean , Hammerschmitt Peter , Weiss Raymond
Published: July 2007

The synthesis of new zirconium and hafnium bisporphyrinate double deckers M(P)2 (MZr, Hf; POEP, TPP)2,3) is described. The complexes are characterized by UV/Vis/NIR and 1H‐NMR spectroscopy and cyclic voltammetry. As compared with MCe, the redox potentials or the energies of the nearinfrared absorption bands of the corresponding radical cations [M(P)2]+ are lower by ≈︁ 0.2 V or higher by ≈︁ 2000 cm−1, respectively, Hence, there is a stronger π‐π interaction between the porphyrin ligands as compared with the cerium analogues due to the smaller ionic radii of Zr(IV) and Hf(IV). X‐ray crystallography of Zr(TPP)2 confirms the sandwich‐like structure of the compound and the close proximity of the porphyrin ligands.
Tris(diethylamino)cyclotriboran sowie Konstitutionsisomerie zwischen cyclo;‐ und closo‐Hexakis(diethylamino)hexaboran(6)
Authors: Baudler Marianne , Rockstein Konrad , Oehlert Wolfgang
Published: July 2007

Tris(diethylamino)cyclotriborane and Constitutional Isomerism Between cyclo;‐ and closo‐Hexakis(diethylamino)hexaborane(6)

The reaction of Et2NBCl2 with potassium in boiling cyclohexane provides a mixture of aminopolyboranes, containing 20–25 mol‐% (BNEt2)3 (1), (BNEt2)4 (2), and cyclo;‐(BNEt2)6 (3), respectively, as well as varying amounts of closo;‐(BNEt2)6 (4). Whereas 1 and 3 have been highly enriched by means of HPLC, 4 has been isolated by column chromatography and crystallization. On standing in solution at room temperature, the cyclo‐isomer 3 slowly rearranges to the closo‐isomer 4, while at elevated temperatures the reverse conversion occurs. Hence 4, which is the first neutral B6 compound with octahedral structure, has a relatively higher thermodynamic stability at normal conditions.
Substituenteneffekte auf die CC‐Bindungsstärke, 10. Resonanzstabilisierung von Alkylradikalen durch zwei geminale Cyangruppen
Authors: Pakusch Joachim , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

Effects of Substituents on the Strength of C–C Bonds, 10. – Resonance Stabilization of Alkyl Radicals by Two Geminal Cyano Groups

The activation parameters of the homolytic cleavage of the Cq – Cq bonds of several dialkylated malonodinitriles (2–5) and of 1,1,2,2‐tetracyanoethane (7) and the heat of dissociation of 6 in solution have been determined. Together with the ground state strain of the radical precursors (obtained from the heats of combustion or EFF calculations) the steric influence on the dissociation process has been determined. The resonance stabilization energy of α,α'‐dicyanoalkyl radicals then calculated was (12.4 ± 0.9) kcal/mol. This result is discussed within the concept of capto‐dative stabilization. The destabilizing interaction of two geminal cyano groups is apparently the same in the ground state of 2 – 7 and the radicals generated from them.
Chiral Organometallic Reagents, I Stereoselective Exchange of Diastereotopic Bromine Atoms by Lithium in 1,1‐Dibromo‐3‐(trimethylsilyloxy)alkanes
Authors: Hoffmann Reinhard W. , Bewersdorf Martin , Kr üger Michael , Mikolaiski Wolfgang , St ürmer Rainer
Published: July 2007

Bromine‐lithium exchange in 1,1‐dibromo‐3‐(trimethylsilyl‐oxy)alkanes 4 and 6 affords the carbenoids 8 and 14, which have been added to ketones, aldehydes, arylboronates, and silylating agents. Diastereoselectivity in the generation and trapping of the carbenoids ranged between 70 – 90% for 8 and >90% for 14.
Chiral Organometallic Reagents, II. Equilibration of Diastereomeric Carbenoids, the tert‐Butyl 2‐Bromo‐2‐lithio‐1‐methylcyclopropanecarboxylates
Authors: Schmidt Armin , Köbrich Gert , Hoffmann Reinhard W.
Published: July 2007

The diastereomeric carbenoids 6 are generated at ‐125°C from the dibromocyclopropane 5 by halogen‐metal exchange and trapped by electrophiles. Since the resulting carbenoids 6 equilibrated by halogen‐metal exchange with their precursor dibromo compound 5, the product ratios depend strongly on the reaction conditions used. Normal addition of n‐butyllithium favors equilibration giving “thermodynamic ratios” of the carbenoids. Inverse addition of 5 to tert‐butyllithium approaches the “kinetic ratio” of carbenoids, which is revealed in reactions in which the carbenoids are trapped in situ by alcohols. The carbenoids 6 have been found to be configurationally stable at ‐125°C. They undergo rapid equilibration at temperatures above ‐78°C before decomposition sets in at ‐60°C.
Gas‐Phase Thermolysis, 14. On the Isomerization of Dimethyl Carbonate and Its Mono‐, Di‐, and Trithio Analogs
Authors: Egsgaard Helge , Carlsen Lars , Sülzle Detlev , Schwarz Helmut
Published: July 2007

Gas‐phase pyrolysis of dimethyl carbonate and its mono‐, di‐, and trithio analogs has been performed in the temperature range from 1253 to 1404 K applying the gas phase Curie‐point pyrolysis technique. Real‐time analyses have been carried out by means of mass‐spectrometric techniques. The possible isomerizations of the ester functions have been studied by collisional activation mass spectrometry in combination with appropriate D, 18O, and 34S labeling. It is demonstrated that methyl group migrations can be induced pyrolytically in cases where oxygen‐to‐oxygen or oxygen‐to‐sulfur isomerizations are involved; in contrast, sulfur‐to‐oxygen as well as sulfur‐to‐sulfur isomerizations apparently do not take place.
Die Synthese von Chlor(trichlormethyl)sulfin, Cl3C(Cl)CSO
Authors: Maletzo Christian , Sundermeyer Wolfgang
Published: July 2007

Synthesis of Chloro(trichloromethyl)sulfine, Cl3C(Cl)CSO

The unstable trichlorothioacetyl chloride (2) could be trapped by a Diels‐Alder reaction with anthracene to form the adduct 3, which in turn could be oxidized to the corresponding sulfine adduct 4. Finnaly, chloro(trichloromethyl)sulfine (5) was prepared in good yield by vacuum thermolysis (retro Diels‐Alder reaction) of 4.
Komplexierung von 1,3‐Dihydro‐1,3‐diborapentafulven‐Derivaten mit Fe(CO)3‐Fragmenten: Synthesen, Kristall‐ und Elektronenstruktur von μ‐(η4:η5‐1,3‐Dihydro‐1,3‐diborapentafulven)‐bis (tricarbonyleisen)‐Komplexen
Authors: Feßenbecker Achim , Enders Markus , Pritzkow Hans , Siebert Walter , Hyla‐Kryspin Isabella , Gleiter Rolf
Published: July 2007

Complexation of 1,3‐Dihydro‐1,3‐diborapentafulvene Derivatives with Fe(CO)3 Fragments: Syntheses, Crystal and Electronic Structure of μ‐(η4: η5‐1,3‐Dihydro‐1,3‐diborapentafulvene)‐bis(tricarbonyliron) Complexes

Reactions of the 1,3‐diborapentafulvene derivatives 1a–c with (CO)3Fe(C8H14)2 lead to the violet dinuclear complexes 3a–c, which possess a slipped triple‐decker structure. The X‐ray structure analyses of 3b,c reveal that one Fe(CO)3 group is pentahapto‐coordinated to the 1,3‐diborole frame of C2B2C=C, whereas the other interacts with the Y‐shaped B2C=C unit. The latter resembles the interaction of Fe(CO)3 with trimethylenemethane. An MO calculation indicates that the formation of 3 occurs by distortion of 1 · Fe(CO)3; the slippage of Fe(CO)3 from η5 to η4 bonding is followed by η5 coordination of the second Fe(CO)3 group.
Untersuchung zum Reaktionsverhalten von Nitrilen RCN gegenüber [I3]+[AsF6]− (R = CH3, CF3, Br, I, H)
Authors: Tornieporth‐Oetting Inis , Klapötke Thomas
Published: July 2007

Investigation on the Reactivity of Nitriles RCN towards [I3]+[AsF6]− (R = CH3, CF3, Br, I, H)

The reaction behaviour of cyanogen compounds R — CN (R = CH3, CF3, Br, I, H) towards [I3]+[AsF6]− is investigated. Whereas CF3CN and BrCN do not react, acetonitrile and cyanogen iodide react with the [I3]+ cation to yield the linear species [ICNI]+ and [CH3CNI]+. The different reactivity of RCN towards [I3]+ is discussed on the basis of the substituent electronegativity X(R) and the HSAB principle. Simple thermodynamic estimations (Born‐Haber cycle) explain the greater stability of the (acetonitrile)iodonium cation compared with the inorganic (iodocyan)iodonium salt.
Optische Aktivität und absolute Konfiguration von 1,4‐Dihydroxytricyclo[6.4.0.04,9]dodecan‐7,10‐dion und ‐7‐on
Authors: Jürgensen Micael , Roßnagel Ingrid , Musso Hans
Published: July 2007

Optical Activity and Absolute Configuration of 1,4‐Dihydroxytricyclo[6.4.0.04,9]dodecane‐7,10‐dione and ‐7‐one

(±)‐1,4‐Dihydroxytricyclo[6.4.0.04,9]dodecane‐7,10‐dione (1) has been resolved into the pure enantiomers through chromatographic separation of the diastereomeric dithioacetals 3A and 3B prepared with (‐)‐(2R,3R)‐2,3‐butanedithiol (2). The dithioacetals were converted into the acetals 4, from which the monoketones 6 were obtained by Raney nickel desulfurization/deprotection. The absolute configuration of (1R,4S,8S,9S)‐(‐)‐6 is correlated with that of (1R,4S,8S,9S)‐(‐)‐ 1 by means of Cotton effects and its chromatographic behavior on potato starch. Some interaction between the carbonyl groups in the diketone 1 is demonstrated by comparison of UV, CD, and PE spectra with those of the monoketone 6.
Synthesis, Structure, and Electronic Properties of Bis(tetramethylcyclopropylidene)methane and Bis(cyclopropylidene)methane
Authors: Eckert‐Maksić Mirjana , Zöllner Stephan , Göthling Wolfgang , Boese Roland , Maksimović Ljiljana , Machinek Reinhard , Meijere Armin De
Published: July 2007

Bis(tetramethylcyclopropylidene)methane (5) was prepared by treating 1‐(dichloroethenylidene)‐2,2,3,3‐tetramethylcyclopropane (3) with tert‐butyllithium in the presence of 2,3‐dimethyl‐2‐butene. The parent allene 6 was obtained along a new route from bis(1‐bromocyclopropyl) ketone (11) with low‐valent titanium. Both 5 and 6 show unusually intense allene stretching bands in the IR spectra, and the signals of their central carbon atoms appear at remarkably high field in the 13C‐NMR spectra. The unique structural features of 5 and 6, as evidenced by an X‐ray crystal structural analysis of 5 and 1Jcc values, agree remarkably well with theoretical predictions made by semiempirical (MNDO) and ab initio (4‐31G) calculations and on the basis of the simple picture offered by the hybridization model using the iterative maximum overlap (IMO) approach.
Asymmetrische Synthese chiraler Phosphorverbindungen durch destruktiv‐Oxidation von P(III)‐Verbindungen mittels chiraler Oxaziridine
Authors: Verfürth Uwe , Ugi Ivar
Published: July 2007

Asymmetric Synthesis of Chiral Phosphorus Compounds by Destructive‐Selective Oxidation of P(III) Compounds by Means of Chiral Oxaziridines

From camphor and fenchone chiral N ‐sulfonyloxaziridines (e.g, 7,13) are available that are well‐suited for the destructive‐stereoselective oxidation of P(III) compounds 16. Optimum reagents and reaction conditions for this oxidation are determined by a systematic study. Chiral P(III) and P(V) compounds can thus be prepared from racemic P(III) derivatives.
Zur Alkylierung von 1,3‐Dithietan‐1,1,3,3‐tetroxid (Disulfen) mit Nonafluorbutansulfonsäureestern
Authors: Frasch Markus , Sundermeyer Wolfgang , Waldi Joachim
Published: July 2007

Alkylation of 1,3‐Dithietane 1,1,3,3‐Tetroxide (Disulfene) by Nonafluorobutanesulfonates

Silyl and alkyl esters of nonafluorobutanesulfonic aicd are extremely powerful substitution reagents for disulfenes. Starting from trans‐2,4‐trimethylsilyldisulfene (1) and methyl nonafluorobutanesulfonate (11), 2,4‐dimethyl‐2,4‐bis(trimethylsilyl)‐1,3‐dithietane 1,1,3,3‐tetroxide (2) is prepared. 2 is hydrolyzed to 2,4‐dimethyl‐1,3‐dithietane 1,1,3,3‐tetroxide (3). Rapid H/D exchange reaction of 3 with D2O leads to 4. Compound 3 is deprotonated by aqueous potassium hydroxide and a potassium salt is obtained, the structure of which is most probably 5a. 2,2,4,4‐Tetramethyl‐1,3‐dithietane 1,1,3,3‐tetroxide (7) is obtained from 5 and methyl iodide, i.e. the ring system remains intact, whereas hydrolysis furnishes the ring‐opened product 6. — Three new routes for the synthesis of methyl nonafluorobutanesulfonate (11) via the silver salt 9 or dimethyl sulfate (96% yield) or nonafluorobutanesulfonic anhydride (10) are described.
Carben‐Reaktionen mit Oxetan und mit Oxetan/Methanol‐Gemischen
Authors: Kirmse Wolfgang , Lelgemann Rudolf , Friedrich Klaus
Published: July 2007

Reactions of Carbenes with Oxetane and with Oxetane/Methanol Mixtures

Ethoxycarbonylcarbene, bis(methoxycarbonyl)carbene, phenylcarbene (17a), diphenylcarbene (17b), fluorenylidene (17c), 2‐furylcarbene (31a), 2‐furyl(phenyl)carbene (31b), 4‐oxo‐2,5‐cyclohexadienylidene (40), and 4,4‐dimethyl‐2,5‐cyclohexadienylidene (53) were generated by photolysis of the appropriate diazo compounds. With neat oxetane, most of these carbenes react by competitive C – H insertion (B → A, Scheme 1) and ylide formation (B → C). 31a and 40 do not insert into C – H bonds; 31b does not attack oxetane but rearranges exclusively with formation of 26. The ylides undergo Stevens rearrangement to give tetrahydrofurans (C → D) and α´,β‐elimination, leading to allyl ethers (C → E). With oxetane/methanol mixtures, the intervention of oxonium ions (H) is indicated by the formation of 1,3‐dialkoxypropanes (I). The oxonium ions arise either by protonation of the ylides (C → H) or by protonation of the carbenes (B → G), followed by electrophilic attack of the carbocations (G) at oxetane (G → H). The former route is followed by the alkoxycarbonylcarbenes and by 40; the ylides derived from the remaining carbenes do not react with methanol, owing to their rapid Stevens rearrangements. Protonation of the carbenes 17b, 31, and 53 is clearly indicated by their product ratios and, for 31, by the formation of isomeric ethers (33, 36). The more electrophilic carbenes discriminate but slightly between oxetane and methanol while the more nucleophilic carbenes (17b, 31,53) prefer the protic methanol strongly over the aprotic oxetane.
Activation and Control of the Reaction of Dioxastannolane with Carbon Disulfide and Phenyl Isothiocyanate by the Addition of Bases
Authors: Yano Katsunori , Baba Akio , Matsuda Haruo
Published: July 2007

1,3‐Dioxa‐2‐stannolanes 1 are readlily activated by Lewis bases such as Bu3P and Et3N to give cycloadducts on reaction with carbon disulfide or phenyl isothiocyanate under mild conditions. In particular, bases play a characteristic role in the reaction with carbon disulfide to produce 1,3‐dioxolane‐2‐thiones 2 in good yields, while spiro compounds 3 (1:2 adducts) are predominantly obtained in the absence of bases.
Molecular Structure of Trisilylmethane and Synthesis of 1,1,1‐Trisilylethane
Authors: Schmidbaur Hubert , Zech Joachim , Rankin David W. H. , Robertson Heather E.
Published: July 2007

As a precursor for trisilylmethane, tris(phenylsilyl)methane is prepared by a Merker‐Scott reaction of chlorophenylsilane, bromoform, and magnesium turnings in boiling tetrahydrofuran. Chlorophenylsilane is formed in a new synthesis starting from phenylsilane and hydrogen choride/AlCl3 in diethyl ether. The gas phase structure of trisilylmethane (H3Si)3CH, obtained from (PhSiH2)3CH via (BrSiH2)3CH, has been determined by electron diffraction. Data refinement confirmed a model of C3 molecular symmetry, with local C3v symmetry for the silyl groups. — As a precursor for 1,1,1‐trisilylethane, 1,1,1‐tris(phenylsilyl)ethane has been prepared similarly from chlorophenylsilane, 1,1,1‐trichloroethane and magnesium and converted via 1,1,1‐tris(bromosilyl)ethane into CH3C(SiH3)3.
Thermolabile Kohlenwasserstoffe, 31 Stereoselektive Bildung und Spaltung der Dimeren des 1‐(5,6,7,8‐Tetrahydro‐1‐naphyl)neopentyl‐Radikals
Authors: Peyman Anuschirwan , Beckhaus Hans‐Dieter , Kramer Dirk , Peters Karl , Schnering Hans Georg Von , Rüchardt Christoph
Published: July 2007

Thermolabile Hydrocarbons, 31. – Stereoselective Formation and Cleavage of the Dimers of the 1‐(5,6,7,8‐Tetrahydro‐1‐naphthyl)neopentyl Radical

The 1,2‐diaryl‐1,2‐di‐tert‐butylethanes meso‐ and DL‐6 are synthesised by partial catalytic hydrogenation of the parent dinaphthylethanes 5. The crystal structure of meso‐6 was obtained experimentally and calculated by molecular mechanics methods (MM2). It is shown, that 1‐(5,6,7,8‐tetrahydro‐1‐naphthyl)neopentyl radical 8 forms its dimers 6 with high stereoselectivity, e.g. DL‐6: meso‐6 = 45 (at ‐20°C) and 7.07 (at 100°C). The selectivity was measured over a range of 300 K by using several radical precursors. The difference of the enthalpy of activation has been derived for the two dimerisation reactions: δH†dim(DL – meso) = –2.8 ± 0.2 kcal/mol. The cleavage of DL‐6 and of meso‐6 into 8 was measured kinetically, and the enthalpies of activation δH†dis = 46.2 ± 0.6 (DL‐6) and 52.6 ± 1.3 kcal/mol (meso‐6) and the entropies of activation δ†dis = 8.4 ± 0.6 (DL‐6) and 20.0 ± 2.5 e.u. (meso‐6) have been obtained. A complete thermodynamic cycle is constructed by using the calculated (MM2) heats of formation δH°f = –27.6 (DL‐6) and –30.0 kcal/mol (meso‐6). Thus, the diastereomer (DL‐6), which is formed preferentially, appears to be the thermodynamically and kinetically less stable one. It turns out, that the high stereoselectivity of the dimerisation of 8, compared to the parent 1‐phenyl‐neopentyl radical (2a), is mainly caused by the steric repulsions between the approaching radicals.
Ring‐Chain Tautomerism of 3,5‐Disubstituted 5,6,7,8‐Tetrahydro‐3H‐3H‐[1,2,4]oxadiazolo[4,3‐c]pyrimidine, a Novel Heterocyclic Ring System
Authors: Korbonits DezsÓ , TóbiaAs‐Héja Erzsébet , Simon KÁLmÁN , Kolonits PÁL
Published: July 2007

The reaction of 3‐aminopropionamide oxime (7) with two equiv. of benzaldehyde or of a substituted benzaldehyde gives cis‐3,5‐diaryl‐5,6,7,8‐tetrahydro‐3H[1,2,4]oxadiazolo[4,3‐c]‐pyrimidines (cis‐11a‐c,e). According to 1H‐, 13C‐, and 15N‐NMR studies these compounds form in solution a novel triple tautomeric equilibrium comprising cis‐ and trans‐11a‐c, e and 3‐[2‐(benzylidineamino)ethyl]‐5‐aryl‐4,5‐dihydro‐1,2,4‐oxaliazoles (10a‐c, e). However, the solid obtained from 7 and two equiv. of cinnamaldehyde proved to be an imine (10g), which again formed in solution a similar triple tautomeric system analogously to the mutarotation of sugars. The structure of 11a and 10g was confirmed by X‐ray crystallography.
5,6,7,8‐Tetramethylenebicyclo[2.2.2]oct‐2‐ene as “Bis(diene)” in Repetitive Diels‐Alder Reactions
Authors: Wegener Stefan , Müllen Klaus
Published: July 2007

The synthesis of ladder‐type oligomers by repetitive Diels‐Alder reactions is described. The title compound 1 has been treated with the “bis(dienophile)” 2 at high pressure (7.5 kbar). Under these conditions the formation of oligomers with up to 33 laterally anellated six‐membered rings has been achieved. An attempt has been made to analyze the complex stereochemistry of the cycloadditon by using the model compounds 5a, 5b.
2‐Chloro‐4,5‐dihydroimidazole, VI. Annulation by Means of 4‐(Dimethylamino)pyridine in the Presence of C — H Acids
Authors: Sączewski Franciszek
Published: July 2007

2‐Chloro‐4,5‐dihydroimidazole (1) reacts with 4‐(dimethylamino)pyridine to yield the stable pyridinium salt 2, which on treatment with some C — H acids produces 1,2,3,5‐tetrahydroimidazo[1,2‐α]pyrimidines 6.
Simple Entry into Tricyclo[3.3.0.03,7]octanes
Authors: Hoffmann H. Martin R. , El‐Khawaga Ahmed M. , Oehlerking Hans‐Heinrich
Published: July 2007

1,5‐Dimethylbicyclo[3.3.0]octan‐3,7‐dione (2) was converted into 1,5‐dihydroxy‐3,7‐dimethyltricyclo[3.3.0.03,7]octane (3) in the presence of Sml2 in 76% yield.
Mono‐, Di‐ und Trikomplexierung von 9,10‐Dihydro‐9,10‐dimethyl‐9,10‐diboraanthracen mit Fe(CO)3‐Komplexfragmenten
Authors: Schulz Hartmut , Pritzkow Hans , Siebert Walter
Published: July 2007

Mono‐, Di‐, and Tricomplexation of 9,10‐Dihydro‐9,10‐dimethyl‐9,10‐diboraanthracene with Fe(CO)3 Complex Fragments

Reaction of 9,10‐dihydro‐9,10‐dimethyl‐9,10‐diboraanthracene (1c) with (CO)3Fe(C8H14)2 gives green (CO)3Fe(η6‐1c) (2c), red [(CO)3Fe]2(η4,η6‐1c) (3c), and orange [(CO)3Fe]3(η4,η4,η6‐1c)(4c). The constitutions of 2c, 3c, 4c are derived from NMR and MS data and confirmed by X‐ray structure analyses. In 2c the Fe(CO)3 group is η6‐bonded to the heterocycle of planar 1c. 3c is formed from 2c by complexation of the diene of the benzo ring in anti position. In 4c both benzo rings of 2c are η4‐bonded to the Fe(CO)3 groups anti to the η6‐bonded Fe(CO)3 group.
Synthese und Struktur von Schwefel‐, Schwefelmonoxid‐ und Schwefeldioxid‐ verbrückten dimetallischen Komplexen des Typs [M(CO)(dppm)]2(μ‐S)(μ‐L) und [(CO)3M'(dppm)2MX](μ‐L') (M = Rh, Ir; M' = Mo, W, Mn; L = SO, SO2; L' = S, SO2; X = Cl, CO)
Authors: Heyke Olga , Hiller Wolfgang , Lorenz Ingo‐Peter
Published: July 2007

Synthesis and Structure of Sulfur‐, Sulfur Monoxide‐, and Sulfur Dioxide‐Bridged Dimetallic Complexes of the Type [M(CO)(dppm)]2(μ‐S)(μ‐L) and [(CO)3M'(dppm)2MX](μ‐L') (M = Rh, Ir; M' = Mo, W, Mn; L = SO, SO2; L' = S, SO2; X = Cl, CO)

The homo‐ and heterodimetallic complexes [M(CO)(dppm)]2‐(μ‐S)(μ‐SO2) (M = Rh, Ir) (2a, b), [(CO)3M'(dppm)2MCl](μ‐SO2) (M' = Mo, W; M = Rh, Ir) (4a – c), and [(CO)3Mn(dppm)2‐ Rh(CO)] (6) by passing sulfur dioxide through their solutions. The X‐ray structure analysis of 5a shows the SO2 ligand in a bridging position, whereas one CO ligand is semibridging. Treatment of the same starting materials with thiirane S‐oxide does not lead to the corresponding SO‐bridged dimers, with the only exception of 1b, which yields the new SO complex [(Ir(CO)(dppm)]2(μ‐S)(μ‐SO) (3b). Passing H2S through a solution of 6, the sulfur‐bridged complex [(CO)3Mn(dppm)2‐ Rh(CO)](μ‐S) (8) is formed, accompanied by H2 elimination.
Half‐Sandwich Pentamethylcyclopentadienyl Iridium Complexes Containing Sulfido and Selenido Ligands X‐Ray Crystal Structures of Cp*Ir(PMe3)(S6) and Cp*Ir(PMe3)(Se4)
Authors: Herberhold Max , Ji Guo‐Xin , Rheingold Arnold L.
Published: July 2007

Cp*Ir(PMe3)Cl2 (1) reacts with chalcogenide ligand sources such as (NH4)Sx (x ≈︁ 10), (NEt4)2Se6, and H2Se to yield the half‐sandwich complexes Cp*Ir(PMe3)(Sn) [n = 4 (2a), 6 (4a)] and Cp*Ir(PMe3)(Sen) [n = 2 (5b), 4 (2b)]. Desulfurization of 4a by PPh3 leads to Cp*Ir(PMe3)(S5) (3a), while both 4a and 3a react with excess P(nBu)3 to give 2a. The geometries of the cyclo‐oligochalcogenide ligands in 4a and 2b have been determined by X‐ray crystallography.
Bis(tetraphenylimidodiphosphinato)tin(II) and ‐tin(IV) Dihalides. Conversion of Pseudo Trigonal Bipyramidal to Octahedral Geometry
Authors: Day Roberta O. , Holmes Robert R. , Schmidpeter Alfred , Stoll Karl , Howe Lori
Published: July 2007

The tetraphenylimidodiphosphinate [N‐(P,P‐diphenylphosphinoyl)‐P,P‐diphenylphosphinimidate] ion forms stable bis‐chelates with SnII and SnIV. The SnII compound [N(Ph2PO)2]2Sn (3) displays a distorted Ψ‐tbp structure in the solid state and is fluxional in solution. The bis(imidodiphosphinato)tin dihalides 6 are cis‐structured. A comparison of the X‐ray structures of 3 and the diiodide [N(Ph2PO)2]2SnI2 (6c) indicates the presence of a lone‐pair stereochemical effect in 3 which is absent in 6c.
1,2,3,4,5,6‐Hexa(eq)alkylcyclohexan‐Modellverbindungen für Struktur‐Eigenschafts‐Vergleiche gesättigter discotischer Flüssigkristalle
Authors: Praefcke Klaus , Psaras Panicos , Kohne Bernd
Published: July 2007

1,2,3,4,5,6‐Hexa(eq)alkylcyclohexane Model Compounds for Structure‐Property Comparisons of Saturated Discotic Liquid Crystals

The new hydrocarbon (1α, 2β, 3α, 4β, 5α, 6β)‐hexahexylcyclohexane (19) and a number of new and differently functionalized scyllo‐hexaalkylcyclohexane derivatives (16a, b, 18a – c) with identical stereochemistry were synthesized stereospecifically starting from simple chemical materials. In comparison to the known scyllitol hexaester 1 and the hexaether 2 none of the novel compounds 16, 18, and 19 were thermomesomorphic. This extreme difference in the thermotropic liquid‐crystalline behaviour of the hexa(eq)hydroxycyclohexane (scyllitol) derivatives 1 and 2 on the one hand and of our varied hexa(eq)alkylcyclohexans 16, 18, and 19 on the other obviously is a function of the presence and the position of the element oxygen within the side chains of these symmetric star‐/disc‐shaped compounds. Details concerning this oxygen effect are discussed briefly.
Organische Synthesen mit Übergangsmetall‐Komplexen, 56 Homopyrrole und Dihydropyridine aus N‐Vinylaminocarben‐Eisenkomplexen und Alkinen durch Cyclisierung intermediärer 5‐Aza‐1‐metalla‐1,3,6‐triene
Authors: Aumann Rudolf , Trentmann Beate , Krüger Carl , Lutz Frank
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 561). – Homopyrroles and Dihydropyridines from N‐Vinylamino‐carbene Iron Complexes and Alkynes by Cyclisation of Intermediate 5‐Aza‐1‐metalla‐1,3,6‐trienes

2,3‐Homopyrroles 5 and dihydropyridines 7, 8 are obtained by the light‐induced addition of alkynes 4a – d (RC = CR1; R, R1 = H, CH3, C6H5, CO2CH3) to the N‐vinylaminocarbene iron complex (= 3‐aza‐1‐ferra‐1,4‐diene) 3. The formation of the N‐heterocycles 5 and 7 as well as that of the pyrrolium carbonylferrates 6 can be explained by assuming the chelated 5‐aza‐1‐ferra‐1,3,6‐trienes A to be key intermediates in this reaction. Stereochemical considerations lead to the conclusion that the ring expansion of the 4 1/2‐membered ring of 3 to the 6 1/2‐membered ring of A occurs without prior ≡ decomplexation by the insertion of a C = C unit into the M = C bond. NMR measurements and MNDO calculations suggest that the bicyclic homopyrroles 5 are in equilibrium with the novel monocyclic homopyrrole species 9. The structure of 6c has been established by X‐ray diffraction analysis.
Neue Cyclooctatetraen‐Komplexe des Niobs(1)
Authors: Herberich Gerhard E. , Englert Ullrich , Roos Peter
Published: July 2007

New Cyclooctatetraene Complexes of Niobium[1]

The (butadiene)niobium complexes Cp′Nb(C4H6)2 and Cp′Nb(C4H6)(PMe3)2 (Cp′C5H4Me) react with cyclooctatetraene (COT) to give Cp′Nb(C4H6)(COT) (2), Cp′Nb(COT)2 (3), and Cp′Nb(PMe3)2(COT) (5) with fluxional COT ligands. The structure of 3 exhibits a prone‐η3‐ and a supine‐η4‐COT ligand which interchange their role at elevated temperature. That of 5 shows a supine η3‐COT ligand.
Synthesis, X‐Ray Crystal Structure, and Fluxional Behaviour of fac‐[Ru(CH3CO2)2(PPh3)3] · 2 CH3CO2H
Authors: Lindner Ekkehard , Fawzi Riad , Hiller Wolfgang , Carvill Andrew , McCann Malachy
Published: July 2007

[Ru2(μ‐O2CCH3)4(O2CCH3)] reacts with excess triphenylphosphane in acetic acid to give fac‐[Ru(O2CCH3)2(PPh3)3] · 2CH3CO2H (1), which crystallizes in the triclinic space group P 1− with Z=2. The three phosphane ligands are in the sterically congested facial configuration, and the distorted octahedral geometry around the metal is completed by a unidentate and chelating acetate. A variable temperature 31P{1H}‐NMR study of the complex in CH2Cl2 showed the three phosphanes to be inequivalent at low temperature. On raising the temperature two separate coalescence processes are observed, ultimately making all of the phosphanes equivalent at room temperature. Complex 1 shows slight catalytic activity for the ring‐opening polymerization of bicyclo[2.2.1]hept‐2‐ene (norbornene).
Metal Ion Binding by Dipeptides: Structure of the Product Generated in “Aspartame” Hydrolysis, Sodium cyclo(L‐α‐Aspartyl‐L‐phenylalanine) Tetrahydrate, Na[c(L‐Asp‐L‐Phe)] 4H2O
Authors: Mikulcik Patrizia , Riede ÜRgen , Schmidbaur Hubert
Published: July 2007

Ester cleavage of aspartame (L‐α‐aspartyl‐L‐phenylalanine methyl ester, 1) by equimolar quantities of NaOH is accompanied by intramolecular cyclisation to sodium 3‐benzyl‐6‐(carboxylatomethyl)‐2,5‐dioxopiperazine (2). The solid‐state structure of the crystalline tetrahydrate has been determined by single‐crystal X‐ray diffraction analysis. The cations are arranged in strings, and each sodium atom is in a distorted octahedral environment of six oxygen atoms, including a β‐carboxylato (O1) and an oxo function (O4) of two different dioxopiperazines and four water molecules. No nitrogen coordination is observed. Through the ligand bridging (O1, O4) of the metals and a set of hydrogen bonds involving the amide and carboxylate groups and all water molecules a three‐dimensional network is established.
Zur Energie‐Delle von Diradikalen; III1) 2,3,5,6‐Tetramethylen‐1,4‐cyclohexadiyl
Authors: Roth Wolfgang R. , Langer Reinhard , Ebbrecht Thomas , Beitat Arndt , Lennartz Hans‐Werner
Published: July 2007

Energy Well of Diradicals, III1). – 2,3,5,6‐Tetramethylene‐1,4‐cyclohexadiyl

Gasphase thermolysis of ketone 1 leads to title diradical 3, which in the presence of oxygen yields 5 and peroxides. Assuming that the trapping reaction is collision‐controlled, from the temperature dependence of the competing processes an activation enthalpy of 23 kcal/mol is derived for the recombination of the diradical. By the same technique starting from 5 the heat of formation of the diradical has been determined, ΔH°f(g)=100.8 kcal/mol.
Über die Konformation eines trinuclearen [1.1.1]Tetramethinium‐Cyaninfarbstoffs mit Indolin‐Endgruppen
Authors: Reichardt Christian , Schäfer Gerhard , Knecht Josef , Gärtner Ralf , Allmann Rudolf , Krestel Magda
Published: July 2007

Conformation of a Trinuclear [1.1.1]Tetramethinium Cyanine Dye with Indoline End Groups

According to its ESCA spectrum (Figure 1) and an X‐ray structural analysis (Figure 2), the [1.1.1]tetramethinium cyanine dye 2 exists in the crystalline state and probably also in solution as methinylogous propeller‐like guanidinium ion 2a with approximate C3 symmetry, and not as vinylogous amidinium ion 2b corresponding to a linear β‐substituted trimethine cyanine dye.
Aldol‐ und Michael‐Additionen fluorierter Nitroalkane an Aldehyde, Ketone und α,β‐ungesättigte Carbonylverbindungen1,2)
Authors: Beck Albert K. , Seebach Dieter
Published: July 2007

Aldol and Michael Additions of Fluorinated Nitroalkanes to Aldehydes, Ketones, and α,β‐Unsaturated Carbonyl Compounds1,2)

2,2,2‐Trifluoronitroethane (1) and 3,3,3‐trifluoro‐2‐nitropropane (2), despite their great propensity to undergo HF elimination with base, can be added to aldehydes with KF or neutral alumina (nitroaldol products 7–15). With basic alumina (neat components) they even add to α,β‐unsaturated aldehydes, ketones, esters, and nitriles (γ‐nitro carbonyl derivatives and nitrile 27–35). Doubly lithiated difluoro and trifluoro nitro derivatives (H, L) can be generated from the corresponding nitroethanes and ‐propanes (1–3) with butyllithium (THF, — 100 to −70°C) and added to aldehydes and ketones to give nitroaldols (nitroethanols 11, 12, 16–21) and “homonitroaldols” (nitropropanols 36–38). In essentially all cases, mixtures of diastereoisomers are formed. Through O‐silyltrifluoronitroaldols (22–26) it is possible to enrich one of the diastereoisomers by 3:1 (Scheme 4). Some transformations of the nitro compounds obtained lead to CF3‐substituted aminoethanols (39–46, by catalytic hydrogenation on Raney nickel), a nitrobutanol (30 → 48, with Et3SiH), and a ketone (30 → 49, with Bu3SnH).
Crystalline, Enantiomerically Pure Aldols from a (‐)‐Ephedrine‐Derived N‐Acylimidazolidin‐2‐one
Authors: Drewes Siegfried E. , Malissar Dean G. S. , Roos Gregory H. P.
Published: July 2007

Reaction of (4R,5S)‐1,5‐dimethyl‐4‐phenyl‐3‐propanoylimidazolidin‐2‐one with aromatic aldehydes leads to aldol products which, after one recrystallisation have d. e. s > 99%. Removal of the chiral auxiliary affords optically pure β‐hydroxy esters.
Synthesen neuer bororganischer Ringe mit zwei Bor‐Atomen durch Borylierung des Trimethylenmethan‐Dianions
Authors: Herberich Gerhard E. , Englert Ulli , Ganter Christian , Wesemann Lars
Published: July 2007

Syntheses of New Organoboron Rings with two Boron Atoms by Borylation of the Trimethylenemethane Dianion

Borylation of Li2[C(CH2)3] (1) provides a versatile starting point for the synthesis of 5‐, 6‐, 7‐, and 8‐membered ring systems with two boron atoms and leads to 1,5‐bis(dialkylamino)‐3,7‐dimethylene‐1,5‐diboracyclooctanes 2a, b (a: R=Et; b: R=iPr), 1,3‐bis(dialkylamino)‐5‐methylene‐1,3‐diboracyclohexanes 8a, b, 1,3‐bis(diethylamino)‐5‐methyl‐1,3‐dibora‐4‐cyclo‐hexene (10), and 1,4‐bis(dialkylamino)‐6‐methylene‐1,4‐dibora‐2‐cycloheptenes 11a, b. The compounds 2b, 8b, and the 2,3‐biboratafulvene derivative [Li(TMEDA)]2[CH2C(CHB)2‐(NiPr2)2] are characterized by X‐ray diffraction analysis. It is shown that for trigonal boron B—C(allyl) bond distances (typically 160 ± 1 pm) are significantly larger than B—C(alkyl) distances (typically 158 + 1 pm).
Metalle in Biologie und Medizin, III. Bismutlactat: Darstellung und Strukturchemie eines Hydroxycarboxylat‐Komplexes
Authors: Kiprof Paul , Scherer Wolfgang , Pajdla Liba , Herdtweck Eberhardt , Herrmann Wolfgang A.
Published: July 2007

Metals in Biology and Medicine, III. — Bismuth Lactate: Synthesis and Structure of a Hydroxycarboxylate Complex

As a compound of medical relevance, bismuth (S)‐lactate was synthesized and structurally characterized (single‐crystal X‐ray diffraction). Exploiting the versatile coordination chemistry of carboxylate groups (chelating and bridging ligands), the crystal structure is based upon a three‐dimensional network, showing bismuth in a high coordination number environment.
Darstellung neuartiger monomerer, oligomerer und polymerer Silyltriflate
Authors: Uhlig Wolfram
Published: July 2007

Preparation of New Monomeric, Oligomeric, and Polymeric Silyl Triflates

The highly reactive silyl triflates R3SiOSO2CF3 are valuable reagents in organosilicon chemistry. New triflate derivatives of mono‐ and oligosilanes have been prepared by substitution of phenyl groups or hydrogen atoms for the trifluoromethanesulfonyl group. The presence of the electron‐withdrawing triflate group leads to a strong deactivation of the other substituents at the silicon atom, and the displacement of a second phenyl group at the same silicon atom is much slower than the first step. For this reason in the case of phenylated oligosilanes stepwise monosubstitution of the silicon atoms has been found. Other new oligomeric silyl triflates are obtained by reaction of silanediyl(triyl) bis(tris)(trifluoromethanesulfonates) with lithium derivatives of organosilicon compounds. Finally, the cleavage of silicon–phenyl bonds of poly[methyl(phenyl)silanes] by CF3SO3H leads to triflate derivatives of polysilanes.
Synthese, Struktur und Isomerisierung von Diazaphosphiridinoxiden
Authors: Niecke Edgar , Link Manfred , Nieger Martin
Published: July 2007

Synthesis, Structure, and Isomerization of Diazaphosphiridine Oxides

Herrn Professor Joseph Grobe zum 60. Geburtstag gewidmet.

The 1,2‐Bis(alkyl)iminophosphane, Et3C — P=N — tBu (1), reacts with nitroso compounds, RNO (R=tBu, Ph), to form the diazaphosphiridine oxides, Et3C — YYP(=O) — NtBu — NYYR, 4a, b. While 4a (R=tBu) is thermally stable, 4b (R=Ph) isomerizes with formation of the benzodiazaphosphole oxide Et3C — YYP(= O) — NH — C6H4 — NYYtBu (5). The corresponding phospholimine Et3C — YYP(=NtBu) — NH — C6H4 — NYYtBu (7) has been obtained from 1 and azobenzene. The three‐membered phosphorus heterocycle 4a has been characterized by X‐ray structure analysis, which reveales some remarkable features.
Coordinated versus Noncoordinated Isocyanides: Synthesis of Complexes CH3C(CH2NC)x[CH2NC—Cr(CO)5]3‐x(x=1, 2) and Crystal Structure of CH3C(CH2NC)2[CH2NC — Cr(CO)5]
Authors: Ekkehardt Hahn F. , Tamm Matthias
Published: July 2007

The triisocyanide ligand CH3C(CH2NC)3 reacts with Cr‐(CO)5(THF) depending on the stoichiometry to give the complexes CH3C(CH2NC)x[CH2NC—Cr(CO)5]3‐x (x=1, 2). The complex CH3C(CH2NC)2[CH2NC — Cr(CO)5] has been characterized by an X‐ray structure analysis allowing a direct comparison of the bonding parameters of coordinated and noncoordinated isocyanide ligands in the same molecule.
Alkyleisen‐ und Alkylcobalt‐Reagenzien, III. Nichtstabilisierte Eisenalkyle: Bildung, Nachweis und Chemoselektivität
Authors: Kauffmann Thomas , Laarmann Barbara , Menges Detlef , Neiteler Gabriele
Published: July 2007

Alkyliron and Alkylcobalt Reagents, III. — Nonstabilized Ironalkyls: Formation, Detection, and Chemoselectivity

The crystalline ate complex Me4FeLi2(Et2O)2 (1 d) described in the literature as well as the complexes MeFeCl (1a), Me2Fe (1b), Me3FeLi (1c), nBu2Fe (2 a), nBu4FeLi2 (2b), nOct2Fe (3a), nOct3FeLi (3b), and nOct4FeLi2 (3c) are prepared in situ by transmetallation of MeLi, nBuLi, and nOctLi with FeCl2 (readily available by in situ reduction of FeCl3 with MeLi). All these complexes have been subjected to reaction with organic substrates for the first time. Evidence for this transmetallation has been furnished by a novel test (referred to as “β‐bromostyrene‐ketone test”). In this test, involving addition of β‐bromostyrene (4) and 4‐methylpentan‐2‐one (5), the alkyllithium compounds alkylate selectively only the ketone and the alkyliron compounds almost exclusively the β‐bromostyrene. The high preference of the alkyliron reagents for the alkylation of the β‐bromostyryl residue has been utilized for regioselective butylations and octylations of 1‐{4‐[(Z)‐2‐bromoethenyl]phenyl}‐ethanone (6). Moreover, in competition reactions with benzaldehyde/4‐methylpentan‐2‐one the alkyliron reagents have been found to react usually specifically with aldehydes. The decomposition temperatures of the reagents 1a,b,c and 2b in THF have been determined to be 0, −10, 25, and −20°C, respectively.
Epoxidation of 2,3‐Dimethylbenzofurans by Dimethyldioxirane
Authors: Adam Waldemar , Bialas Joachim , Hadjiarapoglou Lazaros , Sauter Markus
Published: July 2007

The synthesis of epoxides 2 by the reaction of the chloro‐ and methyl‐substituted 2,3‐dimethylbenzofurans 1 with dimethyl‐dioxirane at low temperature is reported. These labile epoxides were spectroscopically characterized (1H and 13C NMR) at subambient temperatures. Epoxidation of benzofuran 1c affords a 31:69 mixture of epoxide 2c and quinone methide 3c, the latter presumably being produced by valence isomerization of the epoxide. On warming up above −10°C, the epoxides 2 suffer decomposition. Treatment of epoxide 21 with methanol yields the tautomeric mixture of adducts 4i and 4i′.
Organische Synthesen mit Übergangsmetall‐Komplexen, 57. 4,5‐Homotropilidene durch intramolekulare Cyclopropanierung von (Cycloheptatrienylmethyl)carbenchrom‐ oder ‐wolfram‐Komplexen
Authors: Aumann Rudolf , Runge Martina
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 57[1]. — 4,5‐Homotropilidenes by Intramolecular Cyclopropanation of (Cycloheptatrienylmethyl)carbenechromium or ‐tungsten Complexes

(Cycloheptatrienylmethyl)carbene complexes LnM=C(OEt)‐CH2C7H7 [3: LnM=Cr(CO)5 (a), W(CO)5 (b)] are obtained in yields of 80% by the reaction of the corresponding methylcarbene complexes LnM=C(OEt)CH3 1 with tropylium tetrafluoroborate (2) in THF/Et3N. Alkylation of 3 with 2 gives [bis(cycloheptatrienyl)methyl]carbene complexes LnM=C(OEt)CH(C7H7)2 [4: LnM=Cr(CO)5 (a), W(CO)5 (b)]. Thermolysis of 3 leads to the formation of an equilibrium mixture of the 4,5‐homotropilidenes 5 and 6. According to NMR measurements and AM1 calculations the formation of 6 is strongly favored. An equilibrium between 4,5‐homotropilidene complexes is significantly different from that of the metal‐free ligands. By the reaction of 5/6 with bis(ethylene)rhodium 1,3‐pentanedionate (8) the complexes 9 and 10 of both 4,5‐homotropilidenes 5 and 6 are obtained in a 1:3 ratio. The (1,5‐diene)rhodium(I) complexes 9 and 10 are nonfluxional and configurationally moderately stable at 20°C. The reaction of 5/6 with Fe2(CO)9 gives the π‐allyl,σ complexes 11 and 12 in a 10:3 ratio, both of which may be derived from the minor 4,5‐homotropilidene isomer 5. In 11 a vinylcyclopropane unit of 5 serves as a four‐electron donor for a Fe(CO)3 group. In 12 the 4,5‐homotropilidene unit is coordinated as a six‐electron donor to a Fe2(CO)6 unit.
Fachinformationszentrum Chemie GmbH, Berlin — A Decade in the Service of Chemistry Information
Authors: Flambard Anthony R. , Weiske Christian M.
Published: July 2007

With the occurrence of the 10th anniversary of the foundation of FIZ CHEMIE in December 1991, a review is given of the historical events leading to the foundation of this government‐sponsored organization, followed by the company's aims and structure, developments during the last decade, and the printed and electronic chemical information and documentation services it offers to education, industry, and the public in general.
Synthese und Reaktionen der Metall‐Base [(C5Me4H)Co(PMe3)2]
Authors: Werner Helmut , Lippert Ferdinand , Peters Karl , Schnering Hans Georg Von
Published: July 2007

Synthesis and Reactions of the Metal Base [(C5Me4H)Co(PMe3)2]

The (tetramethylcyclopentadienyl)cobalt complex [(C5Me4H)Co(PMe3)2] (1), which is prepared from [CoCl(PMe3)3] and LiC5Me4H in 75% yield, behaves like a Lewis base and reacts with NH4PF6, CH3I, or CF3SO3CH3 by oxidative addition to give the cations [(C5Me4H)CoX(PMe3)2]+ (X = H, I, CH3; 2–4) isolated as PF6 salts. From 3 (X = I) and excess LiCH3 the dimethylcobalt(III) compound [(C5Me4H)Co(CH3)2(PMe3)] (5) is obtained. Treatment of the corresponding trifluoroacetato derivative [(C5Me4H)Co(PMe3)(OCOCF3)2] (6) with PMe3, P(OMe)3, and 1,2‐C6H4(PPh2)2 leads, in the presence of NH4PF6, to the formation of the cationic complexes 7–9. The displacement of the two PMe3 ligands in 1 by (Ph2P)2NMe gives the rather unstable chelate compound {(C5Me4H)Co[(Ph2P)2NMe]} (10), which on treatment with NH4PF6 is transformed into the stable complex {(C5Me4H)CoH[(Ph2P)2NMe]}PF6 (11). The structure of 11 has been determined by X‐ray diffraction methods.
Arsenosiloxane: Bildung und Zerfall von Trialkylsilyl‐arsenaten und ‐arseniten
Authors: Baier Michael , Bissinger Peter , Schmidbaur Hubert
Published: July 2007

Arsenosiloxanes: Formation and Decomposition of Trialkylsilyl Arsenates and Arsenites

Tris(trialkylsilyl) arsenates(V) are prepared from silver arsenate(V) and chlorotrialkylsilanes or from arsenic acid and hexaalkyldisilazanes. The triethylsilyl ester 1b is stable, but the trimethylsilyl ester 1a undergoes condensation at ambient temperature to give hexamethyldisiloxane and trimethylsilylpolyarsenates(V), including tetrakis(trimethylsilyl) diarsenate(V) (4a). According to an X‐ray crystal structure determination of 4a (triclinic, space group P1) centrosymmetrical dimers are present containing two edge‐sharing AsO6 octahedra with apex‐bridging by two AsO4 tetrahedra. 1a is converted into the salt [(Me3SiO)4As]+ CF3SO3− the cation of which is believed to be a component of the reaction chain. There is also evidence by mass spectrometry for the existence of (Me3SiO)5As (5). — Tris(trimethylsilyl) arsenite(III) (6) is prepared from AsCl3 and NaOSiMe3. With modified stoichiometry, side reactions give also the byproducts Cl2AsOSiMe3, ClAs(OSiMe3)2, Cl2AsOAsCl2, Cl2AsOAsCl(OSiMe3), O[AsCl(OSiMe3)]2, and cyclic chloroarsenosiloxanes (12, 13).
1,2,4‐Oxadithietane und ein 1,2,4‐Oxadithiet
Authors: Gerhardt Rolf , Kuschel Raimund , Seppelt Konrad
Published: July 2007

1,2,4‐Oxadithietanes and a 1,2,4‐Oxadithiete

SO3 adds to (pentafluoro‐λ6‐sulfanyl)ethenes 2 with formation of 1,2‐oxathietane 1 and 1,2,4‐oxadithietanes 3. The latter class of compounds (examples 4a, b) can also be obtained from SO3 and alkylidenesulfur tetrafluorides F3C‐RC = SF4. HOSO2F elimination from 3 affords 3‐methylene‐1,2,4‐oxadithietanes 5. HF elimination from 4a occurs within the ring, resulting in the first oxadithiete 6. This isomerizes upon heating to an alkylidenesulfur difluoride oxide FSO2(F3C)CSF2O.
Reaktionen von Halogenthiazylen: Darstellung, Strukturen und Eigenschaften von perhalogenierten 1,2‐Thiazinen[1]
Authors: Boese Roland , Haas Alois , Heß Thomas
Published: July 2007

Reactions of Halogeno Thiazyls: Preparation, Structures, and Properties of Perhalogenated 1,2‐Thiazines

Reactions of (XSN)n(n= 1,3; X = F, Cl) with perfluorobutadiene provide the 1λ4,2‐thiazines1aand1b. The structure of1 bwas determined by single‐crystal X‐ray diffraction analysis. From the molecular structure it is evident that a formal [4 + 2] cycloaddition has occured. Fluorination with KF converts1 balmost quantitatively into1 a. The 1λ4,2‐thiazine1 adoes not exhibit fluorinating properties towards chloroalkanes but undergoes reaction with CH3OH and Me3SiNMe2to form1 cand1 d, respectively. 1,2‐Thiazine oxide3is obtained from1 aor1 band (Me3Si)2O. Treatment of1 bwith AgAsF6in SO2yields perfluoro‐1,2‐thiazin‐1‐ium hexafluoroarsenate (4) as the main product. No reaction is observed between FSN and hexa‐chlorobutadiene. The 1,2‐thiazines5, 6, and9are prepared from tetrachlorothiophene dioxide (7) and FSN. Fluorine abstraction reactions of5and6with formation of the expected 1,2‐thiazin‐1‐ium ions11and13, respectively, provide evidence for the structures of5and6. These cations are very sensitive to hydrolysis and are converted into the corresponding ketones12and14. The very unstable intermediate CF3SSN, formed on treating Me3SiSCF3or B(SCF3)3with FSN, decomposes to CF3SxCF3(X= 2–4), S4N4, S8, and N2. No addition product can be detected when CF3SSN prepared in situ is treated with dienes.