bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rearrangements of Free Radicals, XIII[1]. Thermal and Photochemical Rearrangements of Cyclic C8H9 Radicals in Adamantane Matrix
Authors: Korth Hans‐Gert , Sustmann Reiner , Sicking Willi , Klärner Frank‐Gerrit , Tashtoush Hasan I. 
Published: July 2007

AbstractThe ESR spectra observed after X‐irradiation of bicyclo‐[5.1.0]octa‐2,5‐diene (homotropylidene) (12) in a [D16]adamantane matrix at 210 K have been identified to be mainly due to the cyclooctatrienyl radical (8), formed by thermal ring opening of the initial bicyclo[5.1.0]octa‐2,5‐diene‐4‐yl (homotropylidenyl) radical (7). The same spectrum has also been observed in X‐irradiation of bromocyclooctatriene and a mixture of bromocyclooctatriene and 7‐bromobicyclo[4.2.0]cycloocta‐2,4‐diene in a [D16]adamantane matrix. In all cases, UV irradiation of the matrix caused an irreversible transformation of radical 8 (and probably 7) into the bicyclo[3.3.0]octa‐2,6‐diene‐4‐yl radical (17). Tricyclo[3.3.0.02,4]oct‐6‐en‐7‐yl radical (19), generated by X‐irradiation of tricyclo[3.3.0.02,4]oct‐2‐ene (20) in adamantane, is thermally stable up to 370 K, but also undergoes a facile rearrangement to the radical 17 on UV irradiation. This process is reasonably explained to occur stepwise via radicals 7 and 8. The postulated reaction paths and the spectral assignments are supported by semiempirical (AM1, PM3), abinitio (UHF/3‐21G*), and molecular mechanics (MM2ERW) calculations, which are in accord with the finding that 8 is energetically more stable than 7. The quantum mechanical calculations predict that a degenerate sigmatropic circumambulation of the cyclopropane ring in radical 7 should favorably compete with its ring opening.
Relationship between Dominant Conformation and Diastereoselectivity of O‐Acetal Formation of Saturated 2H‐3,1‐Benzothiazine‐2‐thiones
Authors: Perjési Pál , Batta Gyula 
Published: July 2007

AbstractStereospecific formation of O‐acetals 4, 5 of the isomeric octahydro‐8a‐hydroxy‐4‐phenyl‐2H‐3,1‐benzothiazine‐2‐thiones 1–3 is reported. The stereoselectivity of the reaction is determined by the dominant conformations. During all reactions the phenyl substituent retains its equatorial position.
Alkylierungsreaktionen mit Alkoholen und Kohlenmonoxid: Eine breit anwendbare Synthese von Thioethern und von Coffein aus Theophyllin
Authors: Bott Kaspar 
Published: July 2007

Alkylation Reactions by Means of Alkanols and Carbon Monoxide: An Efficient Synthesis of Thioethers and of Caffeine from TheophyllineThe reaction of sodium or potassium thiolates with alkanols and carbon monoxide provides a versatile route to produce thioethers in excellent yields. By analogy, the potassium salt of theophylline suffers a nearly quantitative conversion to caffeine when heated with methanol under CO pressure. The mechanism of these alkylation reactions is discussed.
Beiträge zur Chemie des Bors, 219. (Di‐tert‐butylphosphanylimino)(2,2,6,6‐tetramethylpiperidino)boran: ein BNP‐1,3‐”︁Dipol”
Authors: Kroner Jürgen , Nöth Heinrich , Polborn Kurt , Stolpmann Holger , Tacke Matthias , Thomann Martina 
Published: July 2007

Contributions to the Chemistry of Boron, 219[1]. – (Di‐tert‐butylphosphanylimino)(2,2,6,6,‐tetrametylpiperidino)borane: a BNP 1,3‐„Dipole”In contrast to amino‐imino‐boranes R2N–BN–R', which are susceptible to [2 + 2] cycloadditions, the amino(phosphanyl‐imino)borane 2 [R = P(tBu)2] performs [3 + 2] cycloadditions with heteroallenes XCY or nitriles to yield the novel five‐membered heterocycles 3a–g, 6, 7, and 8. The reactions of 2 are dominated by the phosphorus atom as the nucleophile attacking the carbon atom in XCY and R–CN, respectively. The driving force for the formation of the new heterocycles is obviously provided by the formation of an iminophosphorane structure and a three‐coordinated environment at the boron atom. The X‐ray‐structures of 3a, 3c, 3e, and 3g demonstrate planer heterocyclic rings.
Reaktionen der Hydrazid‐verbrückten Cluster HRu3(CO)9(RN—NR2) mit Alkinen
Authors: Hansert Bernhard , Vahrenkamp Heinrich 
Published: July 2007

Reactions of the Hydrazide‐Bridged Clusters HRu3(CO)9(RN—NR2) with AlkynesThe clusters HRu3(CO)9(RN—NR2) (1) with triply bridging hydrazide ligands (RN—NR2 = MeN—NHMe, HN—NHMe, HN—NMe2) undergo reactions with the alkynes HCCPh and PhCCPh to yield three cluster products in each case. One of them (2) is presumed to result from Ru—H insertion with concomitant cluster opening. The second (3) contains an open Ru3 cluster bridged by a unique μ3‐η2‐vinyl ligand, as shown by a structure determination. The third (4) represents the expected simple reaction product with a s̀,‐bound vinyl ligand, again proved by a structure determination. Cluster type 3 is converted to cluster type 2 by CO addition.
Alkoxy‐substituted N‐acyliminium salts — synthesis, structure, reactivity
Authors: Funke Wolfgang , Hornig Knut , Würthwein Ernst‐Ulrich , Möller Manfred H. 
Published: July 2007

AbstractAlkylation of aliphatic imides 5 by use of oxonium salts takes place at one of the carbonyl oxygen atoms, leading to alkoxy‐substituted N‐acyliminium salts 1. These new reactive intermediates are fully characterized by IR, 1H‐ and 13C‐NMR spectroscopy and X‐ray analysis. The stereochemical and dynamical properties of the model compounds 6, 7 are investigated by ab initio model calculations (MP2/6–31G*//6–31G*). The barrier of rotation around the central C—N bond in 6 is calculated to 10.2 kcal/mol. The reaction with CH acids 8 yields new types of enamides (9); primary amines 10 are converted to N‐acylamidines 11. Primary amidines 12 react with 1 to form new 1,3‐diazabutadiene derivatives 13. The reaction with primary amides 14 gives N,N‐bisacylamidines 15. With primary N‐acylamidines 16 new doubly azavinylogous imides 17 (1‐oxa‐3,5‐diazahexatriene derivatives) are formed.
Studies on thiazolidine‐4,5‐dithiones. Synthesis of 5‐hydrazonothiazolidine‐4‐thiones and 5‐unsubstituted thiazolidine‐4‐thiones
Authors: Kibbel Hans Ulrich , Blödorn Hartmut , Ketcham Roger , Schaumann Ernst 
Published: July 2007

AbstractIn attempts to generate dithiones 3, 4‐thioxothiazolidin‐5‐ones 2a — c were converted into hydrazones 4a — c, which, however, could not be thiolyzed. Also thionation of 2a, b did not provide 3, but resulted in reduction to thiazolidine‐4‐thiones 7a, b.
Organomolybdän‐ und Organowolfram‐Reagenzien, V. über die additive, reduktive Carbonyldimerisierung (ARCD‐Reaktion)
Authors: Kauffmann Thomas , Jordan Jan , Voβ Karl‐Uwe , Wilde Heinz‐Wilhelm 
Published: July 2007

Organomolybdenum and Organotungsten Reagents, V[1]. – On the Additive, Reductive Carbonyl Dimerization (ARCD Reaction)Reagents of the type R4(PrO)4(μ‐PrO)2W2 (3; R = Me, Et, Pr, Bu, sBu, iBu, Hex, Me3SiCH2, Ph) prepared in situ by the action of organolithium or Grignard compounds on (PrO)4(μ‐PrO)2‐W2Cl4 (2), react with aromatic aldehydes or ketones and with the α,β‐unsaturated ketone benzylidene acetone in a novel reaction, called the ARCD reaction, to give products 4 of the type RRRC—CRRR with mostly good yields. In the case of benzylidene acetone and furfural besides the ARCD products the rearranged products 27 and 29 are formed. With the reagent Ph4(PrO)4(μ‐PrO)2W2 (3b) ARCD reactions are also possible in moderate yields with aliphatic aldehydes and ketones. The more closely investigated reagent Me4(PrO)4(μ‐PrO)2W2 (3a; decomposition at about — 45C) tolerates the aromatic bound functional groups Cl, F, OH, OMe, and NMe2 in the substrates, but not the NO2 and CO2Et substituents. It reacts with PhCOX (X = OEt, Cl, OCOPh) via acetophenone to give PhCMe2—CMe2Ph. — For the ARCD reactions a radical mechanism (Scheme 7) is postulated.
Alkylvanadium‐ und Alkylniob‐Reagenzien, III. über zwei unkonventionelle Methoden zur Charakterisierung labiler Organoübergangsmetall‐Komplexe; Anwendungen auf Allylderivate von VIII, VV, CrIII und MnII
Authors: Kauffmann Thomas , Bonrath Werner , Beirich Christoph , Li Weichang , Pahde Claudia , Raedeker Susanne , Wichmann Barbara , Wingbermühle Dorothea 
Published: July 2007

Alkylvanadium and Alkylniobium Reagents, III[1]. – Two Unconventional Chemical Methods for the Characterisation of Labile Transition Metal Complexes; Application to Allyl Derivatives of VIII, VV, CrIII, and MnIITwo little known chemical methods, the “Competition Constant Method” and the production of “Ligand Concentration/Product Yield Diagrams”, are suitable for the characterisation and identification of allyl and crotyl transition metal species prepared in solution. These methods (Figures 1 – 6) gave the following results: by transmetallation of 1 or 2 equivalents of allylMgBr with 1 equivalent of VCl3, CrCl3, or MnCl2 and subsequent reaction with ketones, a diallyl (2, 23, 25) and not a monoallyl derivative of the transition metal reacts with the ketones, suggesting that the equilibrium: 2 allylMCI (allyl)2M + MCl2 (M = VCl, CrCl, Mn) lies far to the right hand side. This assumption was confirmed by the IR spectrum in the case of vanadation of 1 and 2 equivalents of allylMgBr with VCl3 and corresponds with the observation that by chromation of allylMgBr with 1 equivalent of CrCl3 ca. 50% of the CrCl3 remain unaffected although the allylMgBr is completely consumed. Conversely, according to the results of the “Competition Constant Method” vanadation of 1, 2, or 3 equivalents of allylMgBr with VOCl3 gives three different allyl complexes which are believed to be allylVOCl2 (5), (allyl)2VOCl (6), and (allyl)3VO (7). Vanadation of 1 or 2 equivalents of crotylMgBr with 1 or 2 equivalents of VCl3 gives analogous results to the corresponding reactions with allylMgBr.
Structures of tris(donor)‐tris(acceptor)‐substituted benzenes, 5. Organization and reorganization of the π system in a symmetric tris(alkylamino)trinitrobenzene: balance between cyanine and quinoid structures
Authors: Jens Wolff J. , Irngartinger Hermann , Gredel Frank , Bolocan Ion 
Published: July 2007

AbstractThe π system of 1a may adopt markedly different electronic structures with concomitant strong conformational preferences for the six‐membered ring. Neutral 1a can exist either in a quinoid boat form or as a twist boat, formally resulting from the coupling of an anionic with a cationic trimethinecyanine. Deprotonation gives a rigid quinoid boat structure; protonation occurs at a ring atom to form an equally rigid cyanine.
Dendrimere Polyamine
Authors: Moors Rolf , Vögtle Fritz 
Published: July 2007

Dendrimeric PolyaminesThe dendritic amines 2, 3, 4 and the imine 6 are synthesized by a divergent strategy. The formerly problematic reduction of polynitriles is achieved by the use of diisobutylaluminium hydride in high yield. The functional imine dendrimer 6 is converted into its tricobalt complex 7.
Iminophosphane und Azadiphosphiridin‐imine
Authors: Barion Detlef , Gärtner‐Winkhaus C. , Link Manfred , Nieger Martin , Niecke Edgar 
Published: July 2007

Iminophosphanes and Azadiphosphiridine IminesA variety of bis(alkyl)iminophosphanes R—PN—R' 3a—e (R = CMe2Et, CMeEt2, CEt3; R' = CMe3, CEt3) and arylimine‐substitued derivatives [R' = 2,4,6‐tBu3C6H2, R = CEt3 (3f), R = PhCHCH (3g)] are obtained by base‐induced dehydrochlorination from the corresponding amino(chloro)phosphanes R—P(Cl)—N(H)R' 2a—g. Depending on the steric demand of the substituents, the iminophosphanes 3a—d undergo a reversible [2 + 1] cyclodimerization to give the azadiphosphiridine imines R—P(NR')—P(R)—N—R' 4a—d. The same ring system is obtained in the reaction of 3c with the (arylimino)‐phosphanes R—PN—aryl (R = PhCHCH, Et, Me). However, this cycloaddition results in the formation of diastereomers 4e—g and 4'e—g, respectively. The reaction of Et—PN—aryl with R—PN—aryl (R = PhCHCH, Cl) furnishes (phosphanylamino)iminophosphanes Et(R)P—N(aryl)—PNaryl 5a, b. The compounds 3f, 4e, f, and 5a have been characterized by X‐ray structure analyses.
Organosubstituted Heterocycles with CBOBCCN, OPBCCB, and BOBCC Skeletons — Preparation, Characterisation in Solution and in the Solid State[1]
Authors: Köster Roland , Seidel Günter , Müller Gerhard 
Published: July 2007

AbstractThe salts K[magnified imageEt] [A: R2–4 = Et; B: R2,3 = Et, R4 = Ph; C: R2,4 = Et, R3 = Ph; D: R22 = C8H14, R3,4 = Et] react with [Me2NCH2]Br in THF to form the saturated bicyclic amine—tetraalkyldiboroxanes Et(R7)magnified image‐Me2 [1a (X‐ray crystal structure analysis): R1,4,7 = Et; 1b/1b': R1,4 = Et, R7 = syn/anti‐Ph; 1c: R1,7 = Et, R4 = Ph, and 1d/1d': R1,7 = syn/anti‐C8H14, R4 = Et]. A—D react with ClPPh2 to give the six‐membered monocyclic magnified imageEt [2a: R3–5 = Et; 2b: R3,5 = Et, R4 = Ph; 2c: R3,4 = Et, R5 = Ph; 2d (X‐ray crystal structure analysis): R23 = C8H14, R4,5 = Et]. From A—C and ClAsPh2 the 1,2,5‐oxoniadiboratoles magnified imageEt2 [3a: R3,4 = Et; 3b: R3 = Et, R4 = Ph; 3c: R3 = Ph, R4 = Et] are obtained, which rearrange to the 1,2,5‐oxadiborolanes magnified imageEt [4a: R3,4 = Et; 4b/4b': R3 = Et, R4 = Ph; 4c: R3 = Ph, R4 = Et].
1,1‐Organoboration of Di‐1‐alkynylsilanes with Alkynyl Groups of Different Reactivity: New Organometallic‐Substituted Siloles
Authors: Wrackmeyer Bernd , Kehr Gerald , Süβ Jürgen 
Published: July 2007

AbstractThe synthesis of alkynyl[(trimethylstannyl)ethynyl]dimethylsilanes 4 [alkynyl R1—C≡C: R1 = Bu (b), tBu (c), iPent (d), Ph (e), SiMe3 (f)] is reported. The intermolecular 1,1‐ethyloboration of 4 with triethylborane takes place selectively at the Sn—C≡ bond to give first the alkenyl(alkynyl)dimethylsilanes 5 and 6. There exists an equilibrium between 5 and 6, and compound 6 has the suitable stereochemistry for the final intramolecular 1,1‐vinyloboration to form the 4‐(diethylboryl)‐2‐(trimethylstannyl)siloles 7. Protodeborylation of 7 with water gives the 2‐(trimethylstannyl)siloles 8, and protodeborylation and protodestannylation with an excess of acetylacetone affords the siloles 9. Multinuclear NMR (1H‐, 11B‐, 13C‐, 29Si‐, and 119Sn‐) serves for monitoring the reactions and for the characterization of the products.
Strukturen und Moleküleigenschaften sterisch überfüllter Moleküle, 37. Hexakis(trimethylsilylmethyl)benzol C6[CH2Si(CH3)3]6
Authors: Bock Hans , Meuret Jochen , Ruppert Klaus 
Published: July 2007

Structures and Molecular Properties of Sterically Overcrowded Molecules, 37[1]. — Hexakis(trimethylsilylmethyl)benzene C6[CH2Si(CH3)3]6Both the low first vertical ionization energy of only 7.40 eV, determined by PE spectroscopy for C6[CH2Si(CH3)3]6, and the blocked substituent rotation in its radical cation as proven by ESR/ENDOR spectroscopy suggest considerable steric over‐crowdedness. To further substantiate this interpretation of the molecular properties, the crystal structure (hexagonal R3, Z = 2) has been determined at 100 K. Accordingly, the bulky trimethylsilyl groups are arranged alternatingly above or below the C6‐ring plane, out of which the methylene C centers are twisted by ±9°. Due to the angles CCSi widened to 115°, however, the intramolecular distances C(H)(H)C between non‐neighboured methyl groups of 443 and 452 pm even slightly exceed their van der Waals radii sum of 400 pm and thus avoid severe spatial congestion.
Synthese, Struktur und Umlagerung von Chlorbis(2,4,6‐tri‐tert‐butylphenyl)gallan
Authors: Meller Anton , Pusch Stefan , Pohl Ehmke , Häming Ludger , Herbst‐Irmer Regine 
Published: July 2007

Synthesis, Structure, and Rearrangement of Chlorobis(2,4,6‐tri‐tert‐butylphenyl)gallaneThe title compound 1 is easily obtained from GaCl3 and 2 equvialents of supermesityllithium. According to an X‐ray structure analysis one of the supermesityl rings shows a large deviation from planarity. Heating of 1 in vacuo gives mainly two products: an isomer of 1 in which one of the supermesityl groups is bound to Ga by one of its tert‐butyl groups (2) and a benzo[b]gallolane (3) formed by elimination of HCl, X‐ray structure analyses and full NMR (1H, 13C) data are provided for 1 and 2, MS and characteristic NMR (1H, 13C) data for 3.
New Organophosphorus Ligands: 1,1,2‐Tris(diphenylphosphanyl)cyclopropane and Its Derivatives
Authors: Schmidbaur Hubert , Manhart Stefan , Schier Annette 
Published: July 2007

AbstractCyclopropanation of 1,1,2‐tris(diphenylphosphanyl)ethene with dimethylsulfonium methylide affords the title compound 1. The trifunctional phosphane is transformed into the trioxide 2 and trisulfide 3 by oxidation with hydrogen peroxide or elemental sulfur, respectively. With the tetrahydrofuran — borane complex the tris(phosphane—borane) 4 is obtained. The crystal structure of compound 1 has been determined by single‐crystal X‐ray diffraction.
Electronic Interactions in Saturated and Unsaturated [1.1.1]‐, [2.1.1]‐, [2.2.1]‐, and [2.2.2]Triblattanes — PE‐Spectroscopic Investigations
Authors: Gleiter Rolf , Sigwart Christoph , Fessner Wolf‐Dieter , Müller‐Bötticher Hermann , Prinzbach Horst 
Published: July 2007

AbstractThe He(I)‐PE spectra of the parent [1.1.1]‐, [2.1.1]‐, [2.2.1]‐, and [2.2.2]triblattanes 1–4, of their unsaturated or ketonic congeners 5–13 and benzo derivatives 14–20 have been recorded. For 1–4, the energy difference between the highest occupied orbitals (e” and a' mainly localized at the central bicyclo‐[2.2.2]octane unit) and the subsequent MOs increases with increasing number of ethano bridges. This observation is rationalized by using a first‐order perturbation‐theoretical approach. The analysis of the PE spectra of the exo‐methylene (5–7), ketone (8–10), and endo‐olefinic derivatives (11–13) unveils a strong π/σ mixing. The splitting of the π‐bands in 7 (0.95 eV) and 13 (1.0 eV), respectively, is traced back to a stronger π/σ mixing of the e MOs as compared to the a2 MOs. An analogous interaction causes the splitting of the first bands of the ketones 8–10 (0.45–1.49 eV). For the benzo derivatives 14–20 the split of the π‐bands is relatively small (0.35–0.7 eV).
Thermisch induzierte formale [3 + 2]‐Cycloadditionen von 3,3‐Dimethoxycyclopropen an Triazine, eine neue Synthese von Pyrrolo[1,2‐d][1,2,4]triazinen
Authors: Rischke Monika , Seitz Gunther , Frenzen Gerlinde 
Published: July 2007

Thermally Induced Formal [3 + 2] Cycloadditions of 3,3‐Dimethoxycyclopropene to Triazines, a Novel Synthesis of Pyrrolo[1,2‐d][1,2,4]triazinesFormal [3 + 2] cycloaddition reactions of the π‐delocalized singlet vinylcarbene/three‐carbon 1,3‐dipole 8, generated in a reversible, thermal ring opening of the cyclopropenone ketal 7, with a variety of substituted triazines lead to the novel pyrrolo[1,2‐d][1,2,4]triazines 9 or 10. Compound 10c is protonated at N‐2 by HClO4/HOAc to yield the salt 17c and alkylated at the same position by Meerwein reagent [O(CH3)3BF4] to give 18. 10c reacts smoothly with dimethyl acetylenedicarboxylate to provide the pyrido[2,1‐f]pyrrolo[1,2‐d][1,2,4]triazines 19 and 20. The pyrrolotriazine 14 in the presence of oxygen, daylight, and silica gel is readily oxidized to the triazine N‐oxide 22. The crystal structures of 14, of the protonated species 17c and of the N‐oxide 22 have been determined by X‐ray diffraction methods.
Organische Synthesen mit übergangsmetall‐Komplexen, 66. 2‐Aminopyrrole durch Metathese von (β‐Aminovinyl)carben‐Chrom‐ und ‐Wolfram‐Komplexen mit Isocyaniden
Authors: Aumann Rudolf 
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 66[1]. — 2‐Aminopyrroles by Metathesis of (β‐Aminovinyl)carbene Complexes of Chromium and Tungsten with Isocyanides(β‐Aminovinyl)carbene complexes LnMC(OEt)—CHC(Ph)‐NHR (Z)‐3a—d [LnM = (CO)5Cr, (CO)5W; R = Ph, iPr, CH2Ph] react with two equivalents of isocyanides R1—NC 5 (R = c‐C6H11, t‐C4H9) to give 2‐amino‐3‐ethoxypyrroles 7a—e and isocyanide complexes LnM(R1—NC) 6. The reaction involves the formation of ketenimine complexes by metathesis. These are key intermediates. The pyrroles 7 are easily oxidized by air to give amidines PhN(R1NH)C—C(OEt)CH—COPh 9 (R = c‐C6H11, t‐C4H9). 7a forms a Michael adduct 10a as well as a Diels‐Alder adduct 11a with N‐phenylmaleimide. A 1‐amino‐2‐ethoxybenzene 12a is obtained from 11a by elimination of aniline.
The Photoelectron Spectra of Dimethoxysulfane and Dimethoxydisulfane
Authors: Gleiter Rolf , Hyla‐Kryspin Isabella , Schmidt Heinar , Steudel Ralf 
Published: July 2007

AbstractThe He(I) photoelectron spectra of dimethoxysulfane (1) and dimethoxydisulfane (2) have been recorded. The lowest energy ionizations in the PE spectrum of 1 can be explained by assuming C2 symmetry. They can be described as arising from linear combinations between the 3p lone‐pair at sulfur and 2p lone‐pairs at the oxygen atoms. A comparison between the calculated MO sequence of 2 for different conformations and the first PE bands shows a good agreement with an OSSO torsional angle near 90°. The highest occupied MOs of 2 can be described as linear combinations between the 3p MOs of the S2 unit and linear combinations between the 2p AOs of the oxygen atoms.
Verknüpfung von Cyanamiden mit einem Carbinliganden – Bildung von η2‐(C,N)‐Imidazolium‐ und Ansa‐Carben‐Komplexen
Authors: Fischer Helmut , Troll Carsten 
Published: July 2007

Coupling of Cyanamides with a Carbyne Ligand – Formation of η2‐(C,N)‐Imidazolium Complexes and Ansa‐Carbene ComplexesHerrn Prof. Dr. Ernst Otto Fischer zum 75. Geburtstag gewidmet.
Dicarbonyl(cyclopentadienyl)(phenylcarbyne)manganese complexes [Cp(CO)2Mn≡CPh]+X‐ (1‐X) (X = BF4, BCl4) react with dimethyl‐ (2a), diethyl‐ (2b), and diisopropylcyanamide (2c) in five‐fold excess by a head‐to‐tail cyclization of two cyanamides with the carbyne ligand to give η2‐(C,N)‐imidazolium complexes (3a–c–X). As byproducts ansa‐amino(alkylide‐neamino)carbene complexes (4a–c) are formed in which a N=C(Ph) group bridges the carbene carbon and the Cp ring. With increasing excess of the cyanamide the product ratio 3‐X: 4 increases. Among the products of the reaction of 1‐X with the cyanamides N≡CNR2 [NR2 = N(iBu)2, N(Bzl)2, N(Me)Ph] no imidazolium complexes 3‐X are detected, only ansa‐carbene complexes 4 are isolated. PMe3/H2O or pyridine/H2O displaces the heterocyclic ligand from 3a‐BF4. The structure of 3a‐BF4 is established by an X‐ray analysis.
New Organophosphorus Ligands: 1,1,4,4‐Tetrakis(diphenylphosphanyl)butatriene and Its Tetrasulfide
Authors: Schmidbaur Hubert , Manhart Stefan , Schier Annette 
Published: July 2007

AbstractTreatment of bis(diphenylphosphanyl)ethyne with potassium diphenylphosphide in tetrahydrofuran leads to the formation of tetraphenyldiphosphane Ph2P–PPh2 and the title compound (Ph2P)2C=C=C=C(PPh2)2 (1). A mechanism is proposed for this process. Compound 1 reacts with elemental sulfur to give the tetrasulfide [Ph2(S)P]2C=C=C=C[P(S)Ph2]2 (2). The crystal structures of 1 and 2 have been determined by single‐crystal X‐ray diffraction. In both cases the linear butatriene unit shows strongly alternating C=C bond lengths as predicted in theoretical studies.
A Dynamic Equilibrium of Oxaphosphetanes
Authors: Geletneky Christian , Försterling Frank‐Holger , Bock Willi , Berger Stefan 
Published: July 2007

AbstractThe course of the Wittig reaction was investigated by rapid injection NMR spectroscopy. Rate constants for the formation of oxaphosphetanes were determined. A new dynamic equilibrium of oxaphosphetanes was observed for the first time. The solvent and substituent dependence of the new effect was investigated. By labeling various oxaphosphetanes with 13C and 17O the lithium salt dependence of the new equilibrium was shown. A lithium adduct of oxaphosphetanes under these conditions is proposed.