1-Lithio-2,2-diphenyl-1-(phenylsulfonyl)ethen: Synthese und Kristallstruktur

Syntheses and Crystal Structure of 1-Lithio-2,2-diphenyl-1-(phenylsulfonyl)ethene Crystals of [1-lithio-2,2-diphenyl-1-(phenylsulfonyl)ethene]– N,N,N′,N′ -tetramethylethylenediamine (2/2) ( 2 ) were prepared by addition of BuLi to 1,1-diphenyl-2-(phenylsulfonyl)ethene ( 1 ) in the presence of N,N,N′,N′ -tetramethylethylenediamine (TMEDA) at low temperature. The X-ray structure analysis shows a centrosymmetric dimer bridged over an eight-membered (Li? O? S? O)₂ ring. There are no Li–C contacts to the C(α) atoms. Both Li cations are tetracoordinated via the sulfonyl O-atoms and the N-atoms of the TMEDA ligand. The X-ray structure analysis of 1,1-diphenyl-2-(phenylsulfonyl)ethene ( 1 ) also was determined to compare interatomic distances and angles.     

Electronic energy transfer and collection in luminescent molecular rods containing ruthenium(II) and osmium(II) 2,2':6',2"-terpyridine complexes linked by thiophene-2,5-diyl spacers

The electronic absorption spectra, luminescence spectra and lifetimes (in MeCN at room temperature and in frozen n-C3H7CN at 77 K), and electrochemical potentials (in MeCN) of the novel dinuclear [(tpy)Ru(3)Os(tpy)]4+ and trinuclear [(tpy)Ru(3)Os(3)Ru(tpy)]6- complexes (3 = 2,5-bis(2,2':6',2'-terpyridin-4-yl)thiophene) have been obtained and are compared with those of model mononuclear complexes and homometallic [(tpy)Ru(3)Ru(tpy)]4+, [(tpy)Os(3)Os(tpy)]4+ and [(tpy)Ru(3)Ru(3)Ru(tpy)]6+ Complexes. The bridging ligand 3 is nearly planar in the complexes, as seen from a preliminary X-ray determination of [(tpy)Ru(3)Ru(tpy)][PF6]4, and confers a high degree of rigidity upon the polynuclear species. The trinuclear species are rod-shaped with a distance of about 3 nm between the terminal metal centres. For the polynuclear complexes, the spectroscopic and electrochemical data are in accord with a significant intermetal interaction. All of the complexes are luminescent (phi in the range 10(-4)-10(-2) and tau in the range 6-340 ns, at room temperature), and ruthenium- or osmium-based luminescence properties can be identified. Due to the excited state properties of the various components and to the geometric and electronic properties of the bridge, Ru --> Os directional transfer of excitation energy takes place in the complexes [(tpy)Ru(3)Os(tpy)]4+ (end-to-end) and [(tpy)Ru(3)Os(3)Ru(tpy)]6+ (periphery-to-centre). With respect to the homometallic case, for [(tpy)Ru(3)Os(3)Ru(tpy)]6+ excitation trapping at the central position is accompanied by a fivefold enhancement of luminescence intensity.     

Variants of Solid-State and Solution Structures of (η3-Allyl)- {2-[2′-(diphenylphosphino)phenyl]-4,5-dihydrooxazole-P,N}palladium(II) hexafluorophosphates and tetraphenylborates

Crystal and solution structures of the enantiomerically pure and the racemic pairs of (η³-allyl) {2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-phenyloxazole}palladium(II) hexafluorophosphates ( 1 , and rac- 1 , resp.) and tetraphenylborates ( 2 , and rac- 2 , resp.) as well as (η³-allyl){2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-isopropyloxazole}palladium(II) tetraphenylborate ( 3 ) were characterized by X-ray crystallography and ¹H-NMR spectroscopy. In the solid state, rac- 1 and rac- 2 proved to be disordered with both diastereoisomeric complexes in the crystal. The complexes 2 and 3 exist only in the ‘exo’ form. The X-ray structures show that the [Pd^II(η³-allyl)] moiety may adopt different configurations between a nearly symmetrical three-electron Pd^II(π³-allyl) system and an asymmetrical allyl group with a η¹- and a η²-bonding to the metal center. The [Pd^II(η³-allyl)] system of rac- 1 and of ‘endo’ rac- 2 is closer to the former, and that of 2 , ‘exo’-rac- 2 , and 3 closer to the later geometry. The ¹H-NMR spectra of the hexafluorophosphates 1 and rac- 1 show two sets of signals of the allylic protons in an ‘exo’/‘endo’ ratio of 2:3. The tetraphenylborates 2, rac- 2 , and 3 give only one set of broad signals of the allylic protons.     

Structure of a de novo designed protein model of radical enzymes

The use of side chains as catalytic cofactors for protein mediated redox chemistry raises significant mechanistic issues as to how these amino acids are activated toward radical chemistry in a controlled manner. De novo protein design has been used to examine the structural basis for the creation and maintenance of a tryptophanyl radical in a three-helix bundle protein maquette. Here we report the detailed structural analysis of the protein by multidimensional NMR methods. An interesting feature of the structure is an apparent pi-cation interaction involving the sole tryptophan and a lysine side chain. Hybrid density functional calculations support the notion that this interaction raises the reduction potential of the W degrees /WH redox pair and helps explain the redox characteristics of the protein. This model protein system therefore provides a powerful model for exploring the structural basis for controlled radical chemistry in protein.     

Bestimmung spezifischer Oberfl?chen aus der Aktivit?t einer IR-Absorptionsbande

Zusammenfassung Durch Symmetrieerniedrigung der Carbonationen an der Oberfläche von Calcitpräparaten wird die infrarotverbotene symmetrische Valenzschwingung aktiviert.Aus der Intensität dieser Infrarotabsorption kann auf die Oberflächenentwicklung geschlossen werden. Am Beispiel von Cadmiumcarbonat wird durch Vergleich dieser Messungen mit röntgenographischen Methoden der Teilchengrößenbestimmung und BET-Messungen der spezifischen Oberflächen gezeigt, daß die Methode geeignet ist, schnelle Oberflächenbestimmungen durchzuführen.Wir. danken der Deutschen Forschungsgemeinschaft und dem-Verband der Chemischen Industrie für die Förderung dieser Arbeit.     

Metal Complexes with Macrocyclic Ligands. Part XXXIX. Mono- and binuclear copper(II) complexes of a bridging bis[1, 4, 7-triazacyclononane]

The new bis-macrocycle 1, 1′-[(1H-pyrazol-3], 5-diyl)bis(methylene)bis[1, 4, 7-triazacyclononane] ( 1 ) was synthesized and its complexation with Cu²⁺ studied. Potentiometric and spectrophotometric titrations indicate that, in addition to the mononuclear species [Cu(LH₂)]⁴⁺, [Cu(LH)]³⁺, [CuL]²⁺, and [Cu(LH_?1)]⁺, binuclear complexes such as [Cu₂L]⁴⁺, [Cu₂(LH_?1)]³⁺, and [Cu₂(LH_-2)]²⁺ are also formed in solution. The stability constants and spectral properties of these are reported. The binuclear species [Cu₂(LH_?1)]³⁺ specifically reacts with an azide ion to give a ternary complex [Cu₂(LH_?1)(N₃)]²⁺, the stability and structure of which were determined spectrophotometrically and by X-ray diffraction, respectively. The two Cu²⁺ ions are in a square-pyramidal coordination geometry. The axial ligand is one of the N-atoms of the 1, 4, 7-triazacyclononane ring, whereas at the base of the square pyramid, one finds the other two N-atoms of the macrocycle, one N-atom of the pyrazolide and one of the azide, both of which are bridging the two metal centres. In [Cu₂(LH_?1)(N₃)]²⁺, a strong antiferromagnetic coupling is present, thus resulting in a species with a low magnetic moment of 1.36 B.M. at room temperature.     

Mehrkernige Kobaltkomplexe. V. Präparative Herstellung von Tetrakis (äthylendiamin)-μ-peroxo-μ-amido- und μ-peroxo-μ-thiocyanatodikobalt (III)-Komplexen ausgehend von Tetrakis (äthylendiamin)bis-(ammin)-μ-peroxo-dikobalt (III)-tetraperchlorat

Polynuclear Cobalt Complexes. V. Preparation of tetrakis (ethylenediamine)-μ-peroxo-μ-amido and μ-peroxo-μ-thiocyanato-dicobalt (III) complexes starting from tetrakis (ethylenediamine)bis-(ammine)-μ-peroxo-dicobalt (III)-tetraperchlorate Racemic tetrakis (ethylenediamine)-μ-peroxo-μ-amido-dicobalt (III) thiocyanate and its corresponding hydroperoxo- and superoxo-complexes have been isolated from [(en)₂(NH₃)Co(O₂)(NH₃)(en)₂](ClO₄)₄. A new binuclear peroxo complex containing thiocyanate as bridging ligand was prepared by the same method. The stretching frequencies of the CN- and CS-group as well as the NCS-bending frequence in the IR. spectrum of [(en)₂Co(O₂, SCN)Co(en)₂](NO₃)₃ suggest that the μ-thiocyanato group is N-bonded (2050, 750, 475 cm^?1). A comparison of IR. spectra of known singly and doubly bridged μ-peroxo complexes is made. Characteristic absorption bands, assignable to ν(O? O) and ν(Co? O) are given.     

Herstellung,Kristallstruktur und magnetische Eigenschaften von Bis (1,2-benzochinondiimid)-1,2-benzosemichinondiimidokobalt (II)-tetraphenylborat-pentahydrat

Synthesis, Crystal Structure, and Magnetic Properties of Bis(1,2-benzoquinonediimide)-1,2-benzosemiquinonediimidocobalt (II)-tetraphenylborate-pentahydrate Co (II)-salts catalyze the autoxidation of 1,2-diaminobenzene in slightly alkaline solution. Deeply coloured metal complexes are formed during the reaction suggesting intermediate radical or semiquinonediimide stages of the aromatic ligands. Starting from [Co^II (1,2-diaminobenzene)₃] (ClO₄)₂ two different intermediate complexes can be isolated, the magnetic properties of which point to a high-spin cobalt (II)-complex and a low-spin cobalt (II)-complex with a radical ligand respectively. The X-ray structure determination of the latter complex yielded a square pyramidal arrangement, the Co-N₄-plane distance being only 0.5 Å. The dark blue coloured complex is diamagnetic. Two of the aromatic ligands have the oxidation state of a benzoquinonediimide while the third, coordinated by one amino group only, is pseudosemiquinonoid. Crystals of C₄₂H₄₈BCoN₆O₅ are monoclinic, a = 14.493 (5), b = 18.341 (7), c = 15.492 (5) Å, β = 99.198 (5), space group P2¹/n. D_obs. = 1.290, D_calc. = 1.289 g/cm³ for Z = 4. The structure was solved by Patterson's method and refined by least-squares techniques to R = 0.088 for 2866 of 5014 independent reflexions.     

On the numerical treatment of a small divisor problem

Summary Quasiperiodic solutions of perturbed integrable Hamiltonian equations such as weakly coupled harmonic oscillators can be found by constructing an appropriate coordinate transformation which leads to a small divisor problem. However the numerical difficulties are not merely caused by the small divisors but rather by the appearence of ghost solutions, which appear in any reasonable discretization of the problem. Our numerical treatment, based on a Newton-type iteration, guarantees an approximation of the relevant solution of the nonlinear problem. Numerical solutions are found up to a critical value of the coupling constant, which is much larger than the coupling constants allowed by the existence theory available so far.     

Mehrkernige Kobaltkomplexe. IV. Darstellung und Struktur von [(papd)Co(O2)Co(papd)](S2O6)(NO3)2 · 4 H2O1)

Polynuclear Cobalt Complexes. IV. Preparation and Structure of [(papd)Co(O₂)Co(papd)](S₂O₆)(NO₃)₂ · 4 H₂O The binuclear peroxo complex [(papd)Co(O₂)Co(papd)](S₂O₆)(NO₃)₂ · 4 H₂O I crystallizes in the triclinic space group P1 . Lattice constants are a = 9.405(4), b = 9.270(4), c = 12.218(6)Å, α = 89.58(5), β = 99.08(6), γ = 114.79(5)° for Z = 1. The binuclear cation has a center of symmetry, so the Co? O? O? Co unit is planar. Three chelate rings have a common plane, the ligand configuration is δ.