N-Heterocyclic carbenes from ylides of indolyl-imidazolium, azaindolyl-imidazolium, and indolyl-triazolium salts, and their borane adducts

Abstract Indol-2-yl-imidazolium salts were deprotonated at N1 of the indole ring to give ylides. Their tautomeric N-heterocyclic carbenes (NHCs) were trapped by sulfur to give imidazole-2-thiones. Treatment of the ylides with triethylborane resulted in the formation of zwitterionic borane adducts. An analogous sequence of reactions was performed with 8-azaindol-2-yl-imidazolium salts, which served as precursor to prepare first representatives of a new heterocyclic ring system on reaction of their NHC-tautomers with triethylborane. Similarly, an indol-2-yl-1,2,4-triazolium salt was examined with respect to ylide–NHC tautomerism and trapping reactions. A nucleophilic ring transformation of in…

Redox-induced coordination isomerization of a phosphoniobenzophospholide.

1-Triphenylphosphoniobenzo[c]phospholide 1 reacts with [M(CO)(5)Br] (M = Mn, Re) and [Mn(CO)(3)(naphthalene)][BF(4)] to give complexes cis-[M(CO)(4)(1)Br] (5 a,b) and [Mn(CO)(3)(1)][BF(4)] (6 a[BF(4)]), respectively, featuring eta(1)(P)- and eta(5)(pi)-coordination of the phosphole ring. The corresponding reactions with [M(2)(CO)(10)] proceed with conservation of the metal-metal bond and yield, depending on the reaction temperature, dinuclear complexes [M(2)(CO)(8)(1)] (M=Mn, 7 a) or [M(2)(CO)(6)(1)(2)] (M=Mn, Re, 8 a,b) with mu(2)-bridging eta(1)(P):eta(2)(Pdbond;C) coordination of the phosphole moiety. All complexes formed were characterized by spectroscopic data; 5 b, 6 a[BF(4)], and 8 a…

Crystal structures of O-acetylated 2-acylamino-2-deoxy-d-galactose derivatives

The X-ray structures of 1,3,4,6-tetra-O-acetyl-2-deoxy-alpha-D-galactopyranoside derivatives with four different 2-(acylamino) substituents have been determined with Mo K(alpha) radiation at 123 K. The structure of the 2-acetylamino derivative and of its acyl-homologs with a 2-(propanoylamino)-, 2-(butanoylamino)-, and 2-(2-methyl-propanoylamino)-group crystallized in the monoclinic space group C2. The pyranose unit of all compounds has the usual 4C(1) shape. The different orientations of the 6-O-acetyl-groups are discussed. Conformations of the acylamino-group are compared to those found in the crystal structure of N-acetyl-alpha-D-galactosamine.

Cytotoxicity and NMR Studies of Platinum Complexes with Cyclooctadiene Ligands

The synthesis of a series of platinum complexes containing cyclooctadiene ligands with the general structure PtMeL(R-cod) (where L = Cl, I, nC3F7, iC3F7, nC8F17, Me, aryl, alkynyl and R = H, Me, Et, iPr, nBu, iBu, nHex, Ph) is presented. All complexes are remarkably stable and were obtained in excellent yields. Their structure in both solution and the solid state were explored by crystal structures and multinuclear (1H, 13C, 19F, 195Pt) NMR spectroscopy. Cytotoxicity experiments with selected complexes in HeLa cells revealed higher toxicity in comparison to that of cisplatin for most of the structures.

Molecular Ribbons Containing Pyridine Rings

The first synthesis of the ribbon-like compounds 6–10 is described. The new building block diethyl 2,6-bis(bromomethyl)pyridine-3,5-dicarboxylate 1 was prepared and characterized. Single-crystal X-ray structure analyses indicate that these ribbon-like molecules arrange in a folded conformation, with the pyridine and benzene units being folded in a face-to-face manner, and the tosyl units of 8–10 pointing outwards. The “intramolecular self-assembly” (folding) of these molecular ribbons is primarily attributable to the energetically more favourable syn conformation of both the [3.3]metacyclophanes and the pyridinophanes.

Effiziente und stereodivergierende elektrochemische Synthese von optisch reinen Menthylaminen

Template-controlled assembly of ditopic catechol phosphines: a strategy for the generation of complexes of bidentate phosphines with different bite angles.

A rational approach to the synthesis of heterobi- or -trimetallic complexes based upon self-assembly of a flexible ditopic catechol-phosphine ligand with [(cod)PdCl(2)] and simple metal halides such as GaCl(3), BiCl(3), SnCl(4), or ZrCl(4) is described. All products were characterized by spectroscopic and analytical data and single-crystal X-ray diffraction studies. The molecular structures can be described in terms of cis-configured palladium complexes with supramolecular bisphosphine ligands that are formed by the assembly of two phosphine catecholate fragments on a main group/transition metal template. Of particular interest are the distinct decreases in P-Pd-P bite angles and P...P dist…

Syntheses and structure of bis(pentamethylcyclopentadienyl)dithiophosphinato complexes

Bis(pentamethylcyclopentadienyl)phosphane Cp*2PH reacts with sulfur under basic conditions to give the corresponding dithiophosphinate salts M+ CP*2PS−2 (5 M+ = HNEt+3, 6 M+ = Li+), which are formed via the intermediate CP*2P(S)H (4). Both salts on treatment with cobalt(II) chloride give rise to the transition metal dithiophosphinate 7. The structures of this new type of diorganodithiophosphinate complexes in the solid state have been investigated. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 521–525, 1997

Intermolecular oxidative dehydrogenative 3,3′-coupling of benzo[b]furans and benzo[b]thiophenes promoted by DDQ/H+: total synthesis of shandougenine B

With an excess of a strong acid, 2,3-dichloro-5,6-dicyano-1,4-quinone (DDQ) is shown to promote metal-free intermolecular oxidative dehydrogenative (ODH) 3,3'-coupling of 2-aryl-benzo[b]furans and 2-aryl-benzo[b]thiophenes up to 92% yield as demonstrated with 9 substrates. Based on the analysis of oxidation potentials and molecular orbitals combined with EPR, NMR and UV-Vis observations, the studied reaction is initiated by a DDQ-substrate charge transfer complex and presumably proceeds via oxidation of the substrate into an electrophilic radical cation that further reacts with another molecule of a neutral substrate. The coupling reactivity can easily be predicted from the oxidation potent…

Innentitelbild: Effiziente und stereodivergierende elektrochemische Synthese von optisch reinen Menthylaminen (Angew. Chem. 24/2011)

Synthesis of Hydroquinoid C- and O-Biphenyl Disaccharides by Chromium-Templated Benzannulation Reactions

Organometallic monosaccharides 6−10 containing a chromium styrylcarbene skeleton have been synthesized in quantitative yield from O-glycoside methylcarbene complexes 1−5 bearing diisopropylidene-protected glucose, mannose, galactose, or fructose in a trans-selective aldol condensation with benzaldehyde. These compounds undergo a chromium-templated benzannulation upon reaction with ethynyl glucoside to give diastereoisomeric mixtures of Cr(CO)3 complexes. The differences in their thermodynamic stability was exploited in a diastereoselective synthesis of hydroquinoid biphenyl disaccharides 12−16 in 67−88% yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

N-Heterocyclic Phosphenium, Arsenium, and Stibenium Ions as Ligands in Transition Metal Complexes: A Comparative Experimental and Computational Study

Reaction of 2-chloro-1,3,2-diazaarsolenes and -diazaphospholenes with Tl[Co(CO)4] gives instable complexes of type [Co(ER2)(CO)4] which decarbonylated to yield [Co(ER2)(CO)3]. Spectroscopic and X-ray diffraction studies revealed that the tetracarbonyl complexes can be formulated as ion pair for E = P and as covalent metalla-arsine for E = As, and the tricarbonyl complexes as carbene-like species with a formal E=Co double bond. A similar reactivity towards Tl[Co(CO)4] was also inferred for 1,3,2-diazastibolenes although the products were not isolable and their constitution remained uncertain. Evaluation of structural and computational data suggests that the weak and polarized Co–As bond in […

Efficient and stereodivergent electrochemical synthesis of optically pure menthylamines.

Ferrocenylbis(ylene) phosphoranes

The ferrocenylbis(methylene)phosphorane Fc-P(=CTms 2 ) 2 ( 1 ) (Fc = −C 5 H 4 FeC 5 H 5 ) can be synthesized starting from ferrocenyldichlorophosphane FcPCl 2 or ferrocenyldilithiophosphane FcPLl 2 . The X-ray structure of ( 1 ) shows some unusual structural features, which indicate considerable electronic interaction of the ferrocenyl group and the σ 3 λ 5 -phosphorane unit. As a consequence of this interaction, the rotational barrier of the methylene bonds is extraordinary low. Therefore, in contrast to other bis(methylene)phosphoranes, the endo - and exo -Tms groups are indistinguishable on the NMR time scale even at −100°C. The analogous ferrocenylbis(imino)phosphorane Fc-P(=NTms) 2 ( 9…

Adamantan als Baustein neuer Araliphane Synthese, Spektroskopie und Kristallstrukturen

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.

Single and Multiple Additions of Dibenzoylmethane onto Buckminsterfullerene

A novel dibenzoylmethane-fullerene e,e,e-tris adduct was synthesized by the application of a variation of the Bingel–Hirsch conditions and characterized among others by X-ray crystallography. In addition, the corresponding hexakis adduct was detected by MALDI-TOF-MS analysis. Its existence was supported by density-functional-theory (DFT) computations. Furthermore a new synthesis of bis(benzoyl)methanofullerene was established, and its molecular structure was elucidated by X-ray crystallography. DFT computations reproduced the experimentally determined conformation and predict a low energy barrier for the rotation of the two benzoyl moieties.

[3.3]Metacyclophane mit anti ‐Konformation

[3.3]Metacyclophanes with anti Conformation The [3.3]metacyclophanes 5 and 9 with prevailing anti conformation were prepared by using different cyclisation techniques. 1H-NMR studies and X-ray structure analyses of both phanes 5 and 9 prove their unprecedented conformations.

Equipping metallo-supramolecular macrocycles with functional groups: Assemblies of pyridine-substituted urea ligands

A series of di-(m-pyridyl)-urea ligands were prepared and characterized with respect to their conformations by NOESY experiments and crystallography. Methyl substitution in different positions of the pyridine rings provides control over the position of the pyridine N atoms relative to the urea carbonyl group. The ligands were used to self-assemble metallo-supramolecular M(2)L(2) and M(3)L(3) macrocycles which are generated in a finely balanced equilibrium in DMSO and DMF according to DOSY NMR experiments and ESI FTICR mass spectrometry. Again, crystallography was used to characterize the assemblies. Methyl substitution in positions next to the pyridine nitrogen prevents coordination, while …

Synthesis and X-ray structure of amide-based macrocycles, catenanes and pretzelane

The syntheses and crystal structure studies of amide-based catenanes derived from m-phenylene diacrylic acid and 5-acetoxy isophthalic acid (17% and 3% yield of 4a and 4b resp.) and octalactam macrocycles (21% yield of 3) are described. Hydrogen bonding patterns play a key role in the formation of the different conformations of octalactam 3. The crystal structures of 3 reveal a number of hydrogen-bonding interactions between the macrocycle and two different solvent molecules, which are presumably responsible for the different conformations. Furthermore, we report the X-ray structure of a catenane, which was converted into a “pretzelane” by bridging two phenolic hydroxy groups with a p-xylyl…

Bis(pentamethylcyclopentadienyl)-Substituted Phosphanes: Synthesis and Structure

The bis(1,2,3,4,5-pentamethyl-1,3-cyclopentadien-1-yl)phosphanes 3−7 are formed in good yields by the reaction of the halogenophosphanes 2a or 2b with the appropriate nucleophile. Following another route, the dialkylaminobis(pentamethylcyclopentadienyl)phosphanes 11a−c have been synthesized by the treatment of dichloro(dialkylamino)phosphanes with two equivalents of (pentamethylcyclopentadienyl)lithium. The compounds 3−11 have been characterized by multinuclear NMR spectroscopy and 3, 5, 6, and 11a have also been characterized by single-crystal X-ray diffraction studies. The molecular structure of 11a is governed by steric congestion, which typically would lead to a parallel arrangement of …

The transfer of tin and germanium atoms from N-heterocyclic stannylenes and germylenes to diazadienes.

New N-heterocyclic stannylenes and germylenes were synthesized by transamination of E[N(SiMe3)2] (E = Ge, Sn) with alpha-amino-aldimines or ethylidene-1,2-diamines and were characterized by spectroscopic methods and in the case of the germylene 10 g by X-ray diffraction. The reactions of several germylenes and stannylenes with diazadienes were studied by using dynamic NMR and computational methods. Experimental and theoretical studies confirmed that metathesis with exchange of the Group 14 atom is feasible for both stannylenes and germylenes, with exchange rates being generally higher for stannylenes. The metathesis of the diazadiene 3 b and the stannylene 1 b follows second-order kinetics …

[Bis(phosphonio)isophosphindolide]silver complexes

The outcome of reactions of bis(phosphonio)isophosphindolide salts 1[X] and 6[X] (X- Cl-, Br-, CF3SO3-) with silver salts AgY (Y- = CF3SO3-, CF3CO2-, CH3CO2-, 1/2 SO4-) depends strongly on the available anions X, Y. If X-, Y- CF3SO3-, both mononuclear and dinuclear silver complexes are formed which exhibit either μ1,μ1(P) or μ2,η1(P) coordination of the cations 1, 6 to one or to both metals. In solution, dynamic equilibria between both types of products and free 1, 6 were detected by 31P-NMR spectroscopy. Mononuclear (4a, 7) and dinuclear (5a, 8) complexes were isolated as solvates with CHCl3 or THF. If X-, Y- = CF3CO2, only equilibrium mixtures between the free ligands and silver complexes…

Reaction of complex ligands: Part 95. Chromium tricarbonyl complexes of polysubstituted naphthohydroquinones: regioselective synthesis via [3+2+1]-benzannulation and haptotropic rearrangement

Abstract A series of polysubstituted naphthohydroquinoid tricarbonyl chromium complexes were prepared by chromium mediated [3+2+1]-benzannulation of Fischer-type carbene complexes with alkynes. The kinetics and the thermodynamic data of the η6-η6-haptotropic rearrangements were investigated by in-situ NMR spectroscopy. The free activation energies ΔG# range from 23 to 26 kcal mol−1 and only slightly depend on the bulk and the donor/acceptor properties of the substituents. Equilibrium of metal migration was observed for naphthohydroquinone complexes bearing methoxy substituents at the non-hyroquinoid ring (ring A). In complexes bearing methyl groups or only hydrogen substituents at ring A th…

Binding of water and solvent molecules in a 25-membered-ring host compound

The macrocyclic 15- and 25-membered-ring pyridine oligomers 1 and 2 containing three and five methoxy substituents in the 4-position of the pyridine rings were prepared by Muller-Roscheisen cyclization and then isolated by chromatography. They are attractive as synthetic endobasic receptor molecules. X-ray structure analysis exhibits the inclusion of hydrogen-bonded solvent molecules (water and trichloromethane) inside the pentameric macrocycle 2.

Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling

The oxidative treatment of (m)ethyl 2-aryl cinnamates equipped with methoxy groups in position 4 of the phenyl moiety promote the formation of cyclohexadienone substructures. This dealkylative oxidative C–C coupling gives access to spirocyclic compounds and avoids the construction of the corresponding phenanthrenes. Furthermore, the transformation can be expanded to other spirocyclic systems.

Synthesis and reactivity of P-ferrocenylalkylidenephosphanes and related iminophosphanes and diphosphenes

P-Ferrocenyl-substituted alkylidenephosphanes have been prepared and characterized spectroscopically. Their ready conversion to the corresponding acylphosphanes and 1,2-diacyldiphosphanes, as well as a new type of phosphirene synthesis are presented. The X-ray structure of the tetraferrocenyl-substituted diacyldiphosphane has been investigated. Furthermore, P-ferrocenyl iminophosphanes and their complexation behaviour are described. Diferrocenyldiphosphene, which is known to be unstable, has been stabilized by complexation; this has been confirmed by NMR-spectroscopy and X-ray structure analysis.

Inside Cover: Efficient and Stereodivergent Electrochemical Synthesis of Optically Pure Menthylamines (Angew. Chem. Int. Ed. 24/2011)

Structurally diverse second-generation [2.2]paracyclophane ketimines with planar and central chirality: syntheses, structural determination, and evaluation for asymmetric catalysis.

A set of 20 novel [2.2]paracyclophane ketimines with planar and central chirality has been synthesized from enantiomerically pure and racemic 5-acyl-4-hydroxy[2.2]paracyclophane and alpha-branched chiral amines. Their X-ray structures were determined to elucidate the three-dimensional structures and the absolute configuration. The ketimines were used as catalysts in the asymmetric 1,2-addition reactions of diethylzinc with substituted benzaldehydes to furnish chiral alcohols in up to 95 % ee.

Bimetallic Complexes from Amphoteric Group 13/15 Ligands: Syntheses and X-ray Crystal Structures

Bimetallic, pentel-bridged complexes of the type [(dmap)Me 2 -M-E(SiMe 3 ) 2 -M'(CO) n ] (M = Al, Ga; E=P, As, Sb; M'=Cr, Fe, Ni; DMAP= 4-(dimethylamino)pyridine) are formed by reactions of DMAP-coordinated monomeric Group 13/15 compounds [(dmap)Me 2 M-E(SiMe 3 ) 2 ] with the transition metal complexes [(Me 3 N)Cr-(CO) 5 ], [Fe 3 (CO) 1 2 ], and [Ni(CO) 4 ]. For the first time, this reaction offers a general pathway to compounds containing a Group 13 metal and a transition metal bridged by a pentel atom. Complexes prepared in this way were characterized by IR and multinuclear NMR spectroscopy and by single-crystal X-ray structure analysis. Their electronic and structural properties are disc…

Syntheses and reactivity of aminobis(diorganylamino)phosphanes

Aminobis(diorganylamino)phosphanes (R2N)2PNH2 (R = iPr, c-Hex, Ph) (2a–c), were obtained by treatment of the corresponding chlorobis(diorganylamino)phosphanes 1a–c with lithium amide in liquid ammonia. The transition metal phosphane complex (R2N)2(H2N)PNi(CO)3 (3) was prepared by reaction of 2a with tetracarbonylnickel. N-Complexation of 2a with trimethylalane affords the iminophosphorane-alane adduct (R2N)2HP=N(H)AlMe3 (4) by 1,2-H shift from the nitrogen to the phosphorus atom. The corresponding reaction with aluminium trichloride leads to the formation of the salt [(R2N)2HP=N(H)]2AlC12+[AlC14]− (5), in which two iminophosphorane moieties are linked by an AlCl2 bridge. Lithiation of 2a an…

Synthesis and Topological Determination of Hexakis-Substituted 1,4-Ditritylbenzene and Nonakis-Substituted 1,3,5-Tritritylbenzene Derivatives: Building Blocks for Higher Supramolecular Assemblies

Based on trityl moieties, novel organic building blocks have been prepared and structurally investigated. Substituted hexaphenyl-p-xylene (1,4-ditritylbenzene) as well as extended analogues thereof were prepared. Furthermore, a new family based on a 1,3,5-tritritylbenzene motif, connecting three trityl groups through a formal mesitylene unit, was developed. Both families were further converted through six- and nine-fold substitution reactions, respectively, to yield potent molecular building blocks for supramolecular assemblies.

Regioselective acylation of aminoresorcinarenes

Abstract The acid catalyzed hydrolytic cleavage of the oxazine rings in the readily available tetraoxazine derivatives of resorcinarenes results in tetraaminoresorcinarenes. A similar process applied to C2-symmetrical bisoxazine resorcinarene tetratosylates affords C2v-symmetrical resorcinarenediamines. The mild acylation of these resorcinareneamines with BOC-anhydride or para-nitrophenyl ester proceeds selectively at the nitrogen atoms without affecting the hydroxyl groups. Most of the resulting resorcinareneamides are thus obtained in preparative yields and can be easily purified by simple crystallizations. In the crystalline state the compounds obtained are found to bind chloride anions …

ChemInform Abstract: Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling.

Oxidative treatment of 4-methoxy substituted 2-aryl cinnamates leads to an dealkylative C—C coupling and gives access to spirocyclic compounds.

Macrocyclic Ethers and Their Inclusion Complexes

Calixarenes as Stoppers in Rotaxanes

The synthesis of the amide-based rotaxane 7a bearing calix[4]arene blocking groups is described for the first time. While rotaxane formation fails if a calix[4]arene is functionalized at the upper rim with only an amino or methylamino group lacking any spacer, the prolonged amine 5a works successfully as stopper unit preventing dethreading of the dimeric wheel 1a by its size. Rotaxane formation of 8b was observed only by MALDI-TOF mass spectrometry of the reaction mixture of the amine 5b, the axle 6 and 1a. With the larger trimeric wheel 1b no stable rotaxane could be obtained. It either does not act as a concave template or its opening is too wide, even for the bulky calixarene stoppers.

Strukturanalytische Untersuchungen P-substituierter 1,3,2-Diazaphospholidine

2-Diphenylphosphanyl-1,3,2-diazaphospholidines were prepared via metathesis from 2-chloro-1,3,2-diazaphospholidines and LiPPh2. For some of the products, symmetrisation to tetraphenyldiphosphane and 2,2′-bis-1,3,2-diazaphospholidinyls was observed. Most of the derivatives were characterised by single-crystal X-ray diffraction, which showed that all compounds studied feature elongated exocyclic P–Cl or P–P-bonds, respectively. The extent of this bond lengthening is in the P-phosphanyl-substituted species similar and in the P-chloro-derivatives less pronounced than in corresponding CC-unsaturated 1,3,2-diazaphospholenes. Structure correlation involving comparison of exocyclic P–X and endocycl…

Synthesis of 2-anilinobenzimidates, anthranilamides, and 2,3-dihydroquinazolin-4(1H)-ones from N-heterocyclic carbenes of indazole

N-Heterocyclic carbenes of indazole (indazol-3-ylidenes), which are substituted at N1 with aromatics were generated in situ from the corresponding indazolium salts. At 60 °C the indazol-3-ylidenes underwent a ring-opening under N–N bond cleavage to intermediary N-(6-methylenecyclohexa-2,4-dien-1-ylidene)anilines. Trapping of these intermediates by alcohols proved to be a convenient method for the preparation of 2-anilinobenzimidates, which have scarcely been described in the literature. The reaction temperature avoids carbene dimerization, which occurs at −80 °C or rearrangement of the ring-opened intermediate to acridines, which affords 100 °C. Water converted the ring-opened products into…

A versatile metathesis reaction for the formation of labile bonds between group 13 and group 15 atoms.

Novel [6]- and [7]Helicene-Like Quinones via Mono- and Bidirectional Chromium-Templated Benzannulation of Bridged Binaphthyl Carbene Complexes

A new organometallic approach to novel, functionalised, helicene-like quinones and bisquinones has been developed based on the chromium-templated [3+2+1] benzannulation reaction. The [5]helicene-analogous monocarbene chromium complexes 4, 5, 17 and 19, derived from dibromo-substituted methylene- or silylene-tethered binaphthols 2 and 3, react with various alkynes to give [6]helicene-like quinones 6–13 and 20–29 after oxidative work-up. A rare competition of angular vs. linear annulation is observed for the incorporation of phenylacetylene that affords quinones 21/22 and 28/29. Protection of the phenolic benzannulation product with camphanic acid chloride 14, followed by chromatographic sepa…

Island Homoaromaticity in the W-Shaped 2,4-Diphospha-3-arsapentadienide Anion and Related Compounds - Theoretical and Experimental Investigations

A series of anions with general formula (R2C=P)2Pn– (Pn = N, P, As, Sb; R = H, Me, CF3, SiH3, SiMe3, SiF3) was investigated theoretically at the DFT (RI-BP86/TZVP) and RI-MP2/TZVP levels of approximation. Significantly sharpened central PPnP bond angles were predicted for the species with π-acceptor R substituents. The corresponding bond angle values decrease in the order Pn = N >> P > As > Sb. This finding is in agreement with the previously published structural data for [(Me3Si)2C=P]2P–. An island homoaromaticity was proposed as a suitable explanation for the observed effect. In more detail, it consists of shifting negative charge to the electron-withdrawing terminal groups with formation…

Eine vielseitige Metathesereaktion zur Knüpfung labiler Bindungen zwischen Gruppe-13- und Gruppe-15-Elementen

Single and Multiple Additions of Dibenzoylmethane onto Buckminsterfullerene (Eur. J. Org. Chem. 35/2013)

Non-Centrosymmetric Tetrameric Assemblies of Tetramethylammonium Halides with Uranyl Salophen Complexes in the Solid State

Ditopic salophen-UO(2) receptors 1-4 and 7 co-crystallize with tetramethylammonium (TMA) chloride and fluoride salts producing good quality crystals amenable for X-ray diffraction characterization. The arrangement of the receptor and salt units in the crystal lattice is such that tetrameric ball-shaped assemblies are formed, where an inner cluster of four TMA cations are surrounded by an outer shell of four UO(2)-bound anions. These elaborate architectures, which occur in all cases, regardless of a certain degree of structural modification on the receptors, lead to lattices that belong to non-centrosymmetric (NCS) space groups. Interestingly, the tetragonal symmetry of the tetrameric ball-s…

Concave macrobicycles: Absorption spectra, luminescence properties, and endocavital complexation of neutral organic guests

By a mild modified Eglinton coupling a series of diynebridged macrobicyclic hosts capable of endocavital complexation were synthesized and their structures and complexation properties investigated by X-ray analysis. The inclusion of DMSO in 7 suggests a direct correlation between steric fit and orientation of the guest. On the basis of this hypothesis, the orientation of acetone in an endocavital inclusion of 2 was predicted and verified by X-ray analysis. Comparison of the single-crystal X-ray structures of the vacant macrobicycle 3 and of a family of macrobicycles showing endocavital or “pocket” complexation of neutral organic guests suggests that torsion of the cavities upon complexation…

Synthesis of a tetradentate piperazine ligand and a structural study of its coordination compounds

Abstract A tetradentate ligand N,N′-bis(2-pyridylmethyl)piperazine (L1) and seven structures of its transition metal coordination compounds are described. Most of the compounds are of the general formula [M(L1)(NO3)2], with M=Cu2+, Co2+, Mn2+and Cd2+. In addition, a dimeric copper(II) compound, [Cu2(L1)(Ac)4](H2O)3, and polymeric silver(I) compounds, [Ag(L1)]n(NO3)n(EtOH)n and [Ag(L1)]n(SO3CF3)n, were formed. The overall structure of L1 in the metal complexes A–G varies with the size and electronic properties of the metal ions. Mononuclear complex A is a five-coordinated, B is a six-coordinated, and C and D are eight-coordinated metal complexes. The dinuclear Cu complex, E, is four-coordina…

Synthesis of Azido-Glycans for Chemical Glycomodification of Proteins

CCDC 1415863: Experimental Crystal Structure Determination

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CCDC 993792: Experimental Crystal Structure Determination

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CCDC 949721: Experimental Crystal Structure Determination

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CCDC 949723: Experimental Crystal Structure Determination

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CCDC 993789: Experimental Crystal Structure Determination

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CCDC 1565153: Experimental Crystal Structure Determination

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CCDC 1565150: Experimental Crystal Structure Determination

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CCDC 1029374: Experimental Crystal Structure Determination

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