bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalyzed Enantioselective Alkylation of Aldehydes
Authors: Bolm Carsten , Schlingloff Gunther , Harms Klaus 
Published: July 2007

AbstractEnantioselective alkylation of a variety of aldehydes with diethylzinc was achieved by using catalytic amounts of optically active pyridines and C2‐symmetric 2,2′‐bipyridines. The products were obtained in good yields with high enantioselectivities. Steric factors of the catalyst structure which govern the stereoselectivity were revealed, and important reaction intermediates were identified by spectroscopic means and singlecrystal X‐ray diffraction. The effect of additives on the optical purity of the product was studied. A strong asymmetric amplification was found with catalysts of low ee′s.
Erste röntgenographische Charakterisierung N‐lithiierter 4‐Alkyliden‐1,4‐dihydropyridine des Typs [{4‐(CH3CR)C5H4N}Li(TMEDA)]2: Vergleich von Kristall‐ und MNDO‐Strukturdaten sowie Untersuchungen zur Lithium‐Koordination in Lösung
Authors: Anders Ernst , Opitz Andreas , Boese Roland 
Published: July 2007

The First X‐ray Structures of N‐Lithiated 4‐Alkylidene‐1,4‐dihydropyridines [{4‐(CH3CR)C5H4N}Li(TMEDA)]2: Comparison of the X‐ray and MNDO Geometries and Investigation of Lithium Coordination in SolutionThe 4‐ethyl‐ and ‐isopropylpyridines 5a and b were transformed into the lithiated compounds [{4‐(CH3CH)C5H4N}‐Li(TMEDA)]2 (6a) and [{4‐(CH3CCH3)C5H4N}Li(TMEDA)]2 (6b) by reaction with LDA and in the presence of TMEDA. These compounds were recrystallized from a toluene/hexane solution to obtain suitable crystals for X‐ray investigations. Both structures are dimeric containing nonstoichiometric amounts of toluene in the crystals. The structural parameters of the heterocyclic moieties of 6a or b are typical of N‐lithiated 4‐alkylidene‐1,4‐dihydropyridines. MNDO geometries compare quite well with the X‐ray structure of 6a. The lithium atom of 6a in solution prefers the same type of coordination as in the crystal: Two‐dimensional 6Li,1H‐HOESY showed Li contacts only to ortho‐hydrogen atoms (Figure 3). 6a and b react differently with chlorotrimethylsilane (8). The variations of the alkylidene moieties of 6a and b, although seemingly small, are decisive: While the α,α‐dimethyl compound 6b reacts exclusively as an N nucleophile, the α‐methyl compound 6a functions also exclusively as a Cα nucleophile.
The unusual oxidation of a 1,5,2,4‐diazadiphosphorinan‐6‐one with tetrachloro‐ortho‐benzoquinone
Authors: Shevchenko Igor V. , Fischer Axel , Jones Peter G. , Schmutzler Reinhard 
Published: July 2007

AbstractThe oxidation of 2,4‐bis(diethylamino)‐1,5‐dimethyl‐1,5,2,4‐diazadiphosphorinan‐6‐one (1b) with two equivalents of tetrachloro‐ortho‐benzoquinone (TOB) (2) leads to the cleavage of the original heterocycle and to the formation of a mixture of compounds, including the 1,3,2‐diazaphosphetidine 6 (“λ6P‐”) and the spirophosphorane 7. Compound 7 exists as two isomers that undergo slow spontaneous transformation in solution to compound 9, containing a six‐coordinate phosphorus atom. When the oxidation of 1b is carried out in two stages, with the second equivalent of TOB being added after an interval of four days, the cleavage of the original molecule does not occur, and compound 17, containing a seven‐membered ring with two phosphorus atoms of opposite formal charge and different coordination number (“λ4P+,λ6P‐”) is formed. The structures of 6, 7, 9, and 17 were established by low‐temperature X‐ray analysis. Compound 6 displays crystallographic twofold symmetry; the coordination at phosphorus is octahedral, but distorted by the phosphetidine ring. The phosphorus atom in 7 possesses square pyramidal coordination geometry, the pyramid base being defined by the four oxygen atoms. Compound 9 (“λ6P‐”) crystallized with two molecules of CDCl3. Compound 17 crystallized as a dichloromethane solvate. Distorted octahedral and tetrahedral geometries were observed for P1 and P2, respectively. The four‐membered ring is planar. The bridging hydroquinone ligand displays much wider O–C–C(–O) and C–O–P angles than the chelating hydroquinone.
Conversion of ferriosilanes to ferriosilanols by selective oxidation of the sih function by dimethyldioxirane
Authors: Adam Waldemar , Azzena Ugo , Prechtl Frank , Hindahl Kathrin , Malisch Wolfgang 
Published: July 2007

AbstractThe reaction of ferriohydridosilanes Cp(CO)(L)Fe–SiR2H (R = Me, t‐Bu, Ph, o‐Tolyl; L = CO, Ph3P) 1a–e with dimethyldioxirane (as an acetone solution) leads directly to the corresponding ferriosilanols Cp(CO)(L)Fe–SiR2OH 2a–e in moderate to excellent yields.
Benzoanellated centropolyquinanes, 12[1]trifuso‐centrotetraindan – two syntheses of a new centropolyindan
Authors: Kuck Dietmar , Seifert Monika 
Published: July 2007

AbstractTwo independent syntheses of the new centrotetraindan 2, a “trifuso”, Cs‐symmetrical isomer of fenestrindan 1, are described. The first approach is based on the “endo”‐phenyldiindanone 7, which is converted into 2 by benzylation to ketone 8 and subsequent cyclodehydration with polyphoshoric acid. The second, more efficient approach is based on the diindan‐dione 17, which is converted into ketol 19 in two steps, which, in turn, is subjected to a three‐step cyclodehydration‐reduction‐cyclodehydration sequence via 26 and 27 to give 2 in 8% overall yield. Some limits of the cyclodehydration of diindan alcohols and ketones are demonstrated with regard to effects of steric crowding and fragmentation of the carbon skeleton. The steric hindrance of “endo”‐phenyl‐substituted diindans is demonstrated in the case of ketone 26.
Synthese mittlerer und großer Ringe, XXXI[1] Die [6](3,6)Oxepinophan‐[6](2,5)Furanophan‐Ringverengung mit Rutheniumtetroxid
Authors: Tochtermann Werner , Luttmann Kay , Sdunnus Norbert , Peters Eva‐Maria , Peters Karl , Schnering Hans Georg Von 
Published: July 2007

Synthesis of Medium and Large Rings, XXXI[1] – The [6](3,6)Oxepinophane‐[6](2,5)Furanophane Ring Contraction with Ruthenium TetroxideA one‐pot synthesis of the furanophanes 2a and 2b by ring contraction of the oxepinophanes 1a and 1b is described. Evidence is presented that the reaction proceeds by subsequent oxidation of two double bonds via the intermediates 3 and 4. On treatment with hydrochloric acid cis‐4 gives 2a by 1,4‐elimination of hydrogen peroxide. The oxidation of the [7](3,6)oxepinophane 1c leads to a complex mixture of the products 2d and 6–10. 2a undergoes Diels‐Alder reactions with benzyne and 2,3‐naphthalyne to give 11 and 12. The latter forms the stable iron tricarbonyl complex 13. The structures of 2c, 4, 10, 11, and 13 have been established by X‐ray analyses.
Synthese von 3H‐1,2,3,4‐Triazametallol‐Komplexen durch Addition von Azidoameisensäure‐methylester an die Metall – Kohlenstoff‐Dreifachbindung Cyclopentadienyl‐substituierter Carbin‐Komplexe von Molybdän und Wolfram
Authors: Stegmair Claudia M. , Ullrich Waltraud , Schütt Wolfgang , Kiprof Paul , Kreißl Fritz R. 
Published: July 2007

Synthesis of 3H‐1,2,3,4‐Triazametallole Complexes by the Addition of Methyl Azidoformate to the Metal–Carbon Triple Bond of Cyclopentadienyl‐Substituted Carbyne Complexes of Molybdenum and TungstenN3CO2Me attacks the electron‐rich metal–carbon triple bond in C5H5(CO)2 ‐ n (PMe3)nMCR (M = Mo, W; R = Ph, Tol; n = 0, 1) (1) to provide neutral 3H‐1,2,3,4‐Triazametallole complexes 2.
Mehrfach verbrückte Triphenylmethane
Authors: Berscheid Ralf , Vögtle Fritz , Nieger Zzmartin 
Published: July 2007

Multiple‐Bridged TriphenylmethanesUp to fourfold‐bridged macrocyclic compounds bearing triphenylmethane units which form a large molecular cavity were prepared for the first time. The macrobicyclus 4 crystallizes from acetonitrile as 1:1 adduct and from phenylacetonitrile as 1:3 adduct with the respective solvent. The X‐ray structures of these complexes are compared with the related 1:5 adduct of 13 with benzene.
Übergangsmetall‐substituierte Diphosphene, XXVIII. Synthese und Strukturbestimmung der ersten 1,2‐Diaza‐3,4‐diphosphetidine und (2E,8E)‐1,7‐Dioxa‐3,4,9,10‐tetraaza‐5,6,11,12‐tetraphospha‐2,8‐cyclododecadiene
Authors: Weber Lothar , Bastian Holger , Boese Roland , Stammler Hans‐Georg , Neumann Beate 
Published: July 2007

Transition‐Metal‐Substituted Diphosphenes, XXVIII. – Synthesis and Structures of the First 1,2‐Diaza‐3,4‐diphosphetidines and (2E,8E)‐1,7‐Dioxa‐3,4,9,10‐tetraaza‐5,6,11,12‐tetraphospha‐2,8‐cyclododecadienes(η5‐C5Me5)(CO)2FeP  PMes*(Mes*  2,4,6‐tBu3C6H2) reacts with one equivalent of the Δ1‐1,2,4‐triazoline‐3,5‐diones (2a: R = Ph; 2b: R  4‐EtOC6H4) in benzene to give the first 1,2‐diaza‐3,4‐diphosphetidines 3a, b. When the same reaction is performed in diethylether the novel (2E,8E)‐1,7‐dioxa‐3,4,9,10‐tetraaza‐5,6,11,12‐tetraphospha‐2,8‐cyclododecadienes 4a, b are isolated as the sole products. The molecular structures of 3a and 4b are established by single‐crystal X‐ray analysis.
Metal Binding by Amino Acids: Preparation and Crystal Structures of Lithium, Sodium, and Potassium Hydrogen Bis‐L‐pyroglutamate
Authors: Kumberger Otto , Riede Jürgen , Schmidbaur Hubert 
Published: July 2007

AbstractLithium, sodium and potassium hydrogen bis‐L‐pyroglutamate [Li(L‐pGlu)(L‐pGluH)], [Na(L‐pGlu)(L‐pGluH)] and [K(L‐pGlu)(L‐pGluH)], respectively, have been prepared by reaction of aqueous solutions of the metal hydroxides with L‐pyroglutamic acid in the molar ratio 1:2, or in methanol. Crystalline samples of the salts could be obtained by slow evaporation of solutions of the salts in methanol. In the solid state, Li(L‐pGlu)(L‐pGluH) adopts a chain structure with the lithium atoms arranged in double strands. Adjacent metal centers are bridged by the carboxylate groups of the L‐pGlu− ligands. The L‐pGluH ligands are attached to the metal centers through the amide oxygen atoms. Na(L‐pGlu)(L‐pGluH) forms a three‐dimensional coordination polymer with two half‐occupied sodium positions, one L‐pGlu− and one L‐pGluH ligand in the asymmetric unit. The carboxyl and carboxylate groups of the L‐pGluH and the L‐pGlu− ligands are bridging the sodium centers, giving rise to eight‐membered rings, which consist of two sodium atoms, a carboxyl and a carboxylate group. The hydrogen atoms of the carboxyl group of the L‐pGluH ligands are involved in strong hydrogen bonds between a carboxyl and an adjacent carboxylate oxygen atom. K(L‐pGlu)(L‐pGluH) adopts a layer structure with strands of potassium atoms. The metal centers are connected through bridging carboxyl and carboxylate groups of the L‐pGluH and L‐pGlu− ligands, respectively. The structure features eight‐membered ring units comparable to those observed for Na(L‐pGlu)(L‐pGluH), again with the hydrogen atom of the carboxyl group engaged in a strong transannular hydrogen bond. The amide oxygen atoms of the L‐pGlu− and the L‐pGluH ligands are coordinated to the metal centers of adjacent coordination chains. The results of 1H‐ and 13CNMR investigations of aqueous solutions of the compounds indicate extensive electrolytic dissociation in dilute solutions.
Carbonyl O‐Oxides and Dioxiranes: The Influence of Substituents on Spectroscopic Properties
Authors: Bucher Götz , Sander Wolfram 
Published: July 2007

AbstractTriplet 4‐oxocyclohexadienylidenes 6, matrix‐isolated in Ar/ 2% O2 at 10 K, react with triplet O2 on annealing the matrix. Primary reaction products are quinone oxides 4, which have been characterized by IR and UV/Vis spectrometry. They are very photolabile; long‐wavelength irradiation converts them into spiro‐dioxiranes 5, which in turn yield lactones 10 upon irradiation with visible light. Experimental data have been obtained for quinone oxides 4a–g; additionally, ground‐state properties and UV/Vis absorptions of quinone oxides 4a,b and 4e–1 have been calculated by the MINDO‐3/UHF and CNDO/S methods. Since the theoretical and experimental maxima of the π → π* transitions are in good agreement, we conclude that our semiempirical calculations give an adequate picture of quinone oxides 4 which may best be described as dipolar diradicals.
Langgestreckte Moleküle von Dispiro[5.1.5.2]‐Typ
Authors: Boettcher J. , Hartmann R. , Vögtle F. 
Published: July 2007

Rod‐Like Dispiro[5.1.5.2] CompoundsA number of symmetrically and unsymmetrically substituted spiro compounds were synthesized starting from the dispiro[5.1.5.2]trione 1. The trans‐trans isomers of 2, 3, 6–10, and 11 were separated from the cis‐cis and cis‐trans isomers. From the trispiro compound 4 derivatives bearing differing substituents were synthesized. The tetraspiro compounds 5 were obtained in one step. Some of the compounds functionalized with flexible sidegroups show narrow liquid‐crystal phases.
Reaktionen von Komplexliganden, IL. Synthese und Struktur fünf‐ und sechsgliedriger Aminocarben‐C,N‐Chelatkomplexe des Chroms
Authors: Dötz Karl Heinz , Rau Alexander , Harms Klaus 
Published: July 2007

Reactions of Complex Ligands, IL[1]. – Synthesis and Structure of Five‐ and Six‐Membered Aminocarbene‐C,N‐Chelate Complexes of ChromiumAminolysis of pentacarbonyl[methoxy(phenyl)carbene]chromium (1) with cyclic diamines affords the aminocarbene complexes 2, 3, and 6 which undergo a thermally or photochemically induced decarbonylation to give (carbene)tetracarbonyl complexes 4, 5, and 7 containing 5‐ or 6‐membered chelate rings. The X‐ray analysis of 5 indicates a half‐chair conformation for the 6‐membered chelate ring.
Sterische Cyclopentadienyl‐Äquivalente in der Chemie der f‐Elemente: Monomere, homoleptische Lanthanid(III)‐tris[N,N′‐bis(trimethylsilyl)‐benzamidinate]
Authors: Wedler Michael , Knösel Friedrich , Pieper Ursula , Stalke Dietmar , Edelmann Frank T. , Amberger Hanns‐Dieter 
Published: July 2007

Steric Cyclopentadienyl Equivalents in f‐Element Chemistry: Monomeric, Homoleptic Lanthanide(III) Tris[N,N′‐bis(trimethylsilyl)benzamidinates]Anhydrous lanthanide trichlorides react with N‐silylated sodium benzamidinates, Na[4‐RC6H4C(NSiMe3)2], (1a–d), to give the monomeric, homoleptic lanthanide(III) benzamidinates [4‐RC6H4C(NSiMe3)2]3Ln (2–23, R = H, MeO, CF3, Ph). The molecular structure of [4‐MeOC6H4C(NSiMe3)2]3Pr (11) has been determined by X‐ray diffraction. Absorption and emission measurements reveal that the three benzamidinate ligands produce an unusually large crystal field which is comparable with that of cyclopentadienyl.
Phosphorus derivatives of anthracene and their dimers
Authors: Wesemann Jodi , Jones Peter G. , Schomburg Dietmar , Heuer Lutz , Schmutzler Reinhard 
Published: July 2007

AbstractThe syntheses of the (9‐anthracenyl)phosphanes 2 to 7 and of the metal carbonyl complexes 8 and 9 are described. Both 1 and 4 undergo [4 + 4] cycloaddition when irradiated, forming the dimers 10 and 11. Only one of the six possible rotamers for 10 is formed. For 11 one additional rotational isomer is observed. The relationship between the [4 + 4] dimerization and steric effects of the PR2 group is discussed. The compounds 6, 8 and 11 were characterized by X‐ray diffraction. The structure of 6 was rendered imprecise by the presence of disordered toluene, but the influence of the bulky anthracenyl groups was clear, with wide CPC angles of 110.4°. The molecule displays imposed threefold symmetry. The two independent molecules of complex 8, which crystallizes as a dichloromethane hemisolvate, are closely similar to each other; the WP bond lengths are 254.3 and 253.4 pm. The WC bonds trans to phosphorus are 4 pm shorter than those cis. The phosphane dimer 11 crystallizes with imposed centrosymmetry. The H atom positions, which could be tentatively identified from difference syntheses, indicate a different rotamer than was formed for the analogous fluorophosphane dimer 10.
Influence of structural factors and enzyme type on the reactivity and enantioselectivity of the enzymatic esterification of bicyclic meso dialcohols
Authors: Asensio Gregorio , Andreu Cecilia , Marco J. Alberto 
Published: July 2007

AbstractThe meso dialcohols 1–7, obtained from the Diels‐Alder adducts furan/maleic anhydride, furan/dimethyl acetylenedi‐carboxylate, and cyclopentadiene/maleic anhydride, were subjected to enzymatic esterification in organic solvents. A mixture of the corresponding chiral monoacetates and the meso diacetates was obtained. It has been found that reaction rate and enantioselectivity markedly depend on substrate structure, temperature, enzyme type, and nature of the solvent. The presence of an oxygen bridge and an exo configuration are the two structural features which lead to the highest enantioselectivity values.
Model studies of the reduction of 3‐phenyl‐6H‐1,2‐oxazines, chemo‐ and stereoselectivity: synthesis of amino alcohols, amino acids, and related compounds
Authors: Zimmer Reinhold , Hoffmann Matthias , Reißig Hans‐Ulrich 
Published: July 2007

AbstractWhile palladium‐catalyzed hydrogenation of 3‐phenyl‐6H‐1,2‐oxazine 1 produces primary amine 5 in a nitrogen‐transposition reaction, the reductions of the related 1,2‐oxazines 2, 10, and the 1,2‐oxazin‐6‐one 3 afford the expected amino alcohols 4, 11, and the γ‐amino acid 6, respectively, with low diastereoselectivites. In the presence of acetic acid 3 is reductively converted into γ‐keto carboxylic acid 9 and 1 into the γ‐lactam derivative 12 probably by a ring contraction to a nitrone intermediate. Raney nickel as the catalyst is able to transform 1,2‐oxazine 7 bearing an exo‐methylene unit into 3,4‐dihydro‐2H‐pyrrole 13. The reaction of 6H‐1,2‐oxazine 1 with aluminium amalgam produces pyrrole 14 in moderate yield. Treatment of 1 with sodium in 2‐propanol brings about its transformation into pyrrolidine derivative 15 together with pyrrole 14 and amino alcohol 4 as minor products. The chemoselectivity and stereoselectivity of these reductions are discussed including mechanistic proposals for the multistep processes involved.
Inter‐ and intramolecular hetero diels‐alder reactions, 41. Unusual stereocontrol in intramolecular hetero diels‐alder reactions of 2‐Aza‐1,3‐butadienes. A stereoselective sequential synthesis of annulated tetrahydropyridines
Authors: Tietze Lutz F. , Utecht Jens 
Published: July 2007

AbstractCondensation of aldehydes 1a–e with 5‐amino‐3‐methylisoxazole (4) gives the corresponding imines 5a–e with a 2‐aza‐1,3‐butadiene moiety, which cyclize selctively, e.g. 5a to form the trans‐fused tetrahydropyridine 7a and 5c to yield the cis‐fused cycloadduct 8c. The astounding difference in the selectivity of these reactions is explained by electronic effects and suggests a change in the dominating interactions of the orbitals in the transition structure. The structure of 7a is elucidated by an X‐ray analysis.
Photoinduced electron transfer in porphyrin‐quinone cyclophanes, 7. Porphyrin‐quinone cyclophanes with gradually varied acceptor strength: Physical properties related to electron transfer
Authors: Staab Heinz A. , Voit Guido , Weiser Jürgen , Futscher Michael 
Published: July 2007

AbstractAbsorption and emission spectra of the doubly quinone‐bridged porphyrin cyclophanes 1–4 with gradually varied acceptor strength as well as of the single‐bridged analogues 5–9 and 10–13 are reported. Reduction and oxidation potentials of these intramolecular porphyrin‐quinone systems have been determined. Based on these data, fluorescence quenching as well as time‐resolved fluorescence lifetime measurements are discussed in terms of photoinduced electron transfer to the charge‐separated zwitterionic state.
Synthesis of N‐ and p‐(Diphenylmethyl)anilines. ESR Study of their Photofragmentation
Authors: Siskos Michael G. , Garas Stylianos K. , Zarkadis Antonios K. , Bokaris Efthymios P. 
Published: July 2007

AbstractThe reaction of N‐substituted anilines 2 with diphenylmethyl halides 1 at room temperature in the presence of AlCl3 affords p‐substituted derivatives 3 in good yields according to an electrophilic aromatic substitution. In contrast, aniline itself is only converted to the N‐substituted compounds 4. A novel rearrangement from Ph3C‐NHPh (4c) to p‐(triphenylmethyl)‐aniline (5) is described. Unexpected photofragmentations of 4a, b are studied by using ESR and ENDOR spectroscopy; e.g., irradiation of 4b with quartz‐ or pyrex‐filtered light leads to the formation of the radicals Ph2C‐SiMe3 (7b) and Ph2C – NHPh (6) respectively, following selective cleavage of the C – N and C – Si bond.
Vielgliedrige Donor‐substituierte Kohlenwasserstoffringe
Authors: Vögtle Fritz , Schmitz Jürgen , Nieger Martin 
Published: July 2007

AbstractMany‐Membered and Donor‐Substituted Hydrocarbon RingsThe preparation of large rings 2 of the [2n]metacyclophane type by the Müller‐Röscheisen method is described. Yields of cyclic products, potential ligand or host character and ring size can be controlled by intra‐ and extraannular OCH3 groups. The 40‐membered macrocyclus 24 containing eight substituted benzene rings is the largest ring compound of this series isolated so far in pure form. Large substituents OR in position 2 of the starting bis(bromomethyl) compounds lead to higher ring member numbers. The new macrocyclic compounds, with the exception of the “dimer” 7, are all conformationally flexible according to 1H‐NMR spectra. X‐ray structural analyses were performed of the macrocycles 10, 13, 17, and 18; the inclusion of solvent molecules is proven.
Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen, CXX. Niob‐ und Tantalamid–Komplexe sowie neue Cyclocarbodisilazane
Authors: Herrmann Wolfgang A. , Dyckhoff Florian , Herdtweck Eberhardt 
Published: July 2007

Multiple Bonds Between Main–Group Elements and Transition Metals, CXX[1]. – Niobium and Tantalum Amide Complexes and New CyclocarbodisilazanesThe new niobium‐ and tantalum complexes 3a and 3b of formula [(CH3)2 are accesible by the reaction of the oxychlorides MOCl3 with the lithium amide (2) in 30 and 19% isolated yield, resp. The new silazanes cyclo‐[(CH3)2Si(CH2)2Si(CH3)2NH]2 (5) and cyclo‐[(CH3)2Si(CH2)2Si‐(CH3)2NH]3 (6) are prepared from (CH3)2ClSiCH2CH2Si–Cl(CH3)2 and NH3. Their structures – ten‐ and fifteen–membered rings – were determined by single–crystal structure analyses.
Nickel–Zweikernkomplexe mit Ni2E4‐Gerüst (EP, As)
Authors: Scherer Otto J. , Braun Jürgen , Walther Peter , Wolmershäuser Gotthelf 
Published: July 2007

Dinuclear Nickel Complexes with Ni2E4 Framework (EP, As)The photolysis of [Cp4Ni(μ‐CO)]2 (1, Cp4  C5H(iPr)4) and P4 affords [Cp24Ni2P4] (2a) and [Cp4Ni(η3‐P3)] (3a); the thermolysis of 1 and As4 gives [Cp24Ni2As4] (2b) as well as [Cp4Ni(η3‐As3)] (3b). The tetranuclear complex [Cp24Ni2P4{W(CO)5}2] (4) is formed from 2a and [W(CO)5(thf)]. Complexes 2b and 4 have been characterized by X–ray structure analyses.
Preparation and Crystal Structure of Na2[Be(o‐C6H4O2)2] · 5 H2O
Authors: Kumberger Otto , Riede Jürgen , Schmidbaur Hubert 
Published: July 2007

AbstractCrystalline Na2[Be(o‐C6H4O2)2] · 5 H2O was prepared from beryllium hydroxide and a strongly alkaline aqueous solution of catechol. In an X–ray structure determination the complex was shown to feature dianions [Be(o‐C6H4O2)2]2‐ with two chelating catechol ligands. The 9Be–NMR spectrum of an aqueous solution of the compound shows a singlet at δ  7.5. This signal is shifted considerably from the Beaq2+ reference and indicates persistence of the complexation of the metal ion by the catecholate ligands in alkaline aqueous solution. This result is important in the light of the ubiquitous availability of phenolic groups in many biomolecules, such as e.g. catecholamines.