Oxidative addition of small molecules to a dinuclear Au(I) amidinate complex, Au2[(2,6-Me2Ph)2N2CH]2. Syntheses and characterization of Au(II) amidinate complexes including one which possesses Au(II)-oxygen bonds

The dinuclear Au(I) amidinate complex Au2(2,6-Me2Ph-form)2 (1) is isolated in quantitative yield by the reaction of (THT)AuCl and the potassium salt of 2,6-Me2Ph-form in a 1:1 stoichiometric ratio. Various reagents such as Cl2, Br2, I2, CH3I, and benzoyl peroxide add to the dinuclear Au(I)amidinate complex Au2(2,6-Me2Ph-form)2 to form oxidative-addition Au(II) metal-metal-bonded complexes 2, 3, 4, 5, and 6. The Au(II) amidinate complexes are stable as solids at room temperature. The structures of the dinuclear Au2(2,6-Me2Ph-form)2 and the Au(II) oxidative-addition products Au2(2,6-Me2Ph-form)2X2, X=Cl, Br, I, are reported. Crystalline products with an equal amount of oxidized and unoxidized complexes in the same unit cell, [Au2(2,6-Me2Ph-form)2X2][Au2(2,6-Me2Ph-form)2], X=Cl, 2m, or Br, 3m, are isolated and their structures are presented. The structure of [Au2(2,6-Me2Ph-form)2X2][Au2(2,6-Me2Ph-form)2], X=Cl has a Au(II)-Au(II) distance slightly longer, 0.05A, than that observed in the fully oxidized product Au2(2,6-Me2-form)2Cl2, 2. The gold-gold distance in the dinuclear complex decreases upon oxidative addition with halogens from 2.7 to 2.5 A, similar to observations made with the Au(I) dithiolates and ylides. The oxidative addition of benzoyl peroxide leads to the isolation of the first stable dinuclear Au(II) nitrogen complex possessing Au-O bonds, Au2(2,6-Me2Ph-form)2(PhCOO)2, 6, with the shortest Au-Au distance known for Au(II) amidinate complexes, 2.48 A. The structure consists of unidentate benzoate units linked through oxygen to the Au(II) centers. The replacement of the bromide in 3 by chloride, and the benzoate groups in 6 by chloride or bromide also occurs readily. The unit cell dimensions are, for 1, a=7.354(6) A, b=9.661(7) A, c=11.421(10) A, alpha=81.74(5) degrees, beta=71.23(5) degrees, and gamma=86.07(9) degrees (space group P, Z=1), for 2.1.5C6H12, a=11.012(2) A, b=18.464(4) A, c=19.467(4) A, alpha=90 degrees, beta=94.86(3) degrees, and gamma=90 degrees (space group P21/c, Z=4), for 2m.ClCH2CH2Cl, a=16.597(3) A, b=10.606(2) A, c=19.809(3) A, alpha=90 degrees, beta=94.155(6) degrees, and gamma=90 degrees (space group P21/n, Z=2), for 3m, a=16.967(3) A, b=10.783(2) A, c=20.060(4) A, alpha=90 degrees, beta=93.77(3) degrees, and gamma=90 degrees (space group P21/n, Z=2), for 4.THF, a=8.0611(12) A, b=10.956(16) A, c=11.352(17) A, alpha=84.815(2) degrees, beta=78.352(2) degrees, and gamma=88.577(2) degrees (space group P, Z=1), for 5, a=16.688 A, b=10.672(4) A, c=19.953(7) A, alpha=90.00 (6) degrees, beta=94.565(7) degrees, and gamma=90.00 degrees (space group P21/n, Z=4), for 6.0.5C7H8, a=11.160(3) A, b=12.112(3) A, c=12.364(3) A, alpha=115.168(4) degrees, beta=161.112(4) degrees, and gamma=106.253(5) degrees (space group P, Z=1).     

Struktur und elektrochemische Untersuchung von Nb3Cl8

Structure and Electrochemical Study of Nb₃Cl₈ The compound Nb₃Cl₈ was synthesized from NbCl₅ and niobium metal in a sealed quartz ampoule at 700 °C. Single crystals, obtained from LiCl melt were used for X‐ray structure determination (space group P 3 m1, Z = 2, lattice parameters a = b = 672.95(7) pm, c = 1223.2(2) pm (at 100 K), R1 = 0.029, wR2 = 0.064 for all independent reflections). Electrical resistivity measurements are reported. Electrochemical intercalation of lithium into the structure of Nb₃Cl₈ was studied.     

A facile synthesis of pyrrolo[3,2‐d]pyrimidines from 6‐azidouracils and ylide phosphoranes

A series of the title compounds, 9‐deazaxanthines, was regioselectively prepared in reasonable yields as major products from the reactions of 6‐azidouracils 1a,b with stabilized ester‐ 2a,b or keto‐ 2c ylide phosphoranes and a moderated phosphorus ylide 3 , instead of the expected triazoles. Side products were also observed wherein pyrimido[5,4‐g]pteridine‐2,4,5,7‐tetrone ( 15 ) and other fused ring systems or acyclic‐substituted uracil derivatives were isolated. A comparative study on the reactivity of 1a in analogy to 1b toward phosphoranes is also described. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:357–365, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10048     

Magnetic exchange coupling in imido bimetallic uranium(V) complexes. A relativistic DFT study

Magnetic exchange coupling between uranium U(V) ions, in the case of the two para- and meta-imido diuranium complexes, respectively [(C₅H₅)₃U]₂(μ-1,4-N₂C₆H₄) and [(C₅H₅)₃U]₂(μ-1,3-N₂C₆H₄) exhibiting the 5f¹-5f¹ configuration, have been investigated using relativistic DFT calculations, combined with the broken symmetry (BS) approach. Using the B3LYP functional, the singlet BS state of the para complex has been found of lower energy than the high spin (HS) triplet one, in agreement with the observed antiferromagnetic character of the complex. On the contrary the BP86 functional fails to predict this magnetic property. The spin density distributions and MO analysis explain well the antiferromagnetic character of the para complex and clarify the failure of the BP86 functional. The effective participation of the 5f metal orbitals in bonding with the imido ligand plays a key role for electronic and magnetic communication between the two active U(V) 5f¹ electrons. The same technique led us to explain the ferromagnetic character of the meta isomer in agreement with experiment. For both isomers the spin polarization mechanism explains well their observed magnetic behaviour.     

A relativistic DFT study of magnetic exchange coupling in ketimide bimetallic uranium(IV) complexes

Magnetic exchange couplings in bis(ketimide) binuclear U^IV/U^IV complexes [Cp′₂UCl]₂(μ-ketimide) diuranium(IV) and [(C₅H₅)₂(Cl)An]₂(μ-ketimide) (Cp′ = C₅Me₄Et; ketimide = N=CMe-(C₆H₄)-MeC=N) have been investigated computationally using relativistic density functional theory (DFT) combined with the broken symmetry (BS) approach. Using the B3LYP hybrid functional, the BS ground state of these U^IV/U^IV 5f ²–5f ² complexes has been found of lower energy than the high spin (HS) quintet state, indicating an antiferromagnetic character (estimated coupling constant |J| < 5 cm⁻¹) which has not yet been evidenced unambiguously experimentally. On the contrary, the BP86 GGA functional overestimates greatly the antiferromagnetic character of the complexes (|J| > 100 cm⁻¹). As recently reported for para-bis(imido) [(C₅H₅)₃U]₂(μ-imido) uranium(V) complex, spin polarization is mainly responsible for the antiferromagnetic coupling through the π-network orbital pathway within the bis(ketimide) bridge. Furthermore, spin polarization is exalted by the combined roles of the 5f metal orbitals and of the π-conjugated ketimide bridging ligand which permit electronic communication between the two uranium atoms albeit separated by a distance of the order of 10 ?. The MO analysis clarifies which MOs contribute to the antiferromagnetic coupling in the binuclear complexes under consideration and brings to light the 5f orbitals driving contribution.     

On completely integrable coupled Burgers and coupled Korteweg–de Vries systems

In this work, we study two completely integrable equations, namely, coupled Burgers and Korteweg–de Vries systems. The modified form of Hirota’s bilinear method, established by Hereman, is employed to formally derive multiple-soliton solutions and multiple-singular-soliton solutions for each system. Hirota’s bilinear method is reliable and effective and can also be applied to solve other types of higher-dimensional integrable and non-integrable systems.     

Continuous-wave Yb-doped Sc2SiO5 thin-disk laser

We present in this Letter experimental results of a Yb:Sc(2)SiO(5) (Yb:SSO) thin-disk laser. To our knowledge, this is the first lasing demonstration of this crystal in thin-disk configuration reported on to date. Preliminary tests regarding the characterization and the laser operation are presented. Two different resonator configurations, a simple linear multimode cavity, and a fundamental-mode folded resonator providing a double pass in the laser crystal were set up. The gain and the small signal gain of the available Yb:SSO sample were calculated using the experimental results of the multimode resonator. The operation in a fundamental-mode resonator with the double pass in the laser crystal led to 9.4 W of output power with an optical efficiency of 25.4%.     

Structural Diversity Within the Series of 68-Electron M4L n E2 (L = 2-Electron Ligand; M = Fe, Ru, Os, Co; E = CH, N, P, NR, PR, S) Organometallic Clusters: A Theoretical Investigation

Four different skeletal structural arrangements with very different connectivities are known for 6-vertex/68-electron of M₄E₂ core (M = transition metal; E = main-group atom or ligand). DFT calculations on a large number of title model compounds allow to rationalize the preferences between these structural shapes with respect to the nature of the metal and main-group elements constituting the cluster cage. In particular, the electronegativity of M and the “size” (first-row vs. second-row element) of E play an important role in the stability preference of a particular isomer. For several compounds, although only one type of structure is known, other low-energy isomeric forms are also likely to exist. Moreover, two structural types, so far unreported, are predicted to be stable enough for being synthesized.     

New explicit and exact traveling wave solutions for two nonlinear evolution equations

In this paper, with the aid of computer symbolic computation system such as Maple, an algebraic method is firstly applied to two nonlinear evolution equations, namely, nonlinear Schrodinger equation and Pochhammer–Chree (PC) equation. As a consequence, some new types of exact traveling wave solutions are obtained, which include bell and kink profile solitary wave solutions, triangular periodic wave solutions, and singular solutions. The method is straightforward and concise, and it can also be applied to other nonlinear evolution equations in mathematical physics.     

Nash and strongly consistent two-player game forms

A two-player game form is Nash-consistent if and only if it is tight (Gurvich). Therefore Nash-consistency of two-player game forms depends only on the effectivity structure. This fact is no longer true for strong consistency. In this paper we introduce a new object called the joint effectivity structure and define the exact joint effectivity set. These notions are similar though more sophisticated than the usual effectivity functions. We prove that a two-player game form is strongly consistent if and only if it is tight and jointly exact. Joint exactness is a property of the exact joint effectivity set which basically requires that the joint exact effectivity set coincides with the classical effectivity function. As a corollary we have a characterization of two-player strongly implementable social choice correspondences.