Unprecedented association of [Mo6Br(i) 7Y(i)Br(a) 6]3- cluster units and [Mo(III)Br6]3- complexes: synthesis, crystal structures, and properties of the double salts Rb3[Mo6Br(i) 7Y(i)Br(a) 6](Rb3[MoBr6])3 (Y=Se, Te)

The double salts Rb(3)[Mo(6)Br(i) (7)Y(i)Br(a) (6)](Rb(3)[MoBr(6)])(3) (Y=Se, Te) result from the partial disproportionation of the Mo(6)Br(12) octahedral-cluster-based bromide, in the presence of corresponding chalcogenides and RbBr salt (crystal data: Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Te(i)Br(a) (6)] (1), Pm$\bar 3$m (No. 221), a=12.1558(2) A, Z=1, R(1)=0.028; wR(2)=0.050; Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Se(i)Br(a) (6)] (2), Pm$\bar 3$m, a=12.144(3) A, Z=1, R(1)=0.028; wR(2)=0.050). The structures of 1 and 2 are built up from [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units characterised by a random distribution of seven bromine and one chalcogen ligands on all the eight inner positions that face cap the Mo(6) clusters. Such a distribution implies a static orientational disorder of the [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) units around the origin of the unit cell. Close-packed anionic layers based on [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units are stacked in the sequence ABC. This arrangement leads to very short Br(a)--Br(a) intercluster unit distances of 3.252 A, much lower than the sum of the van der Waals radii (3.70 A). The trivalent oxidation state of molybdenum in the Mo complexes and 24 valence electrons per Mo(6) cluster have been confirmed by magnetic susceptibility measurements. Salts 1 and 2 constitute the first examples of structurally characterised bromides containing discrete [Mo(III)Br(6)](3-) complexes obtained by means of solid-state synthesis.     

Surfactant-assisted hollowing of Cu nanoparticles involving halide-induced corrosion-oxidation processes

We have demonstrated a simple fabrication of hollow nanoparticles by halide-induced corrosion oxidation with the aid of surfactants. Cuprous oxide Cu2O nanoshells can be generated by simply mixing Cu nanoparticles with alkyltrimethylammonium halides at 55 degrees C for 16 min. The hollowing mechanism proposed is that absorption of surfactants onto the Cu surface facilitates the formation of the void interior through an oxidative etching process. Upon extending the reaction up to 4 h, fragmentation, oxidation, and self-assembly were observed and the CuO ellipsoidal structures were formed. The headgroup lengths of the surfactants influenced the degree of CuO ellipsoidal formation, whereby longer surfactants favored the generation of ellipsoids. Optical absorption measured by UV-visible spectroscopy was used to monitor both oxidation courses of Cu-->Cu2O and Cu2O-->CuO and to determine the band-gap energies as 2.4 eV for Cu2O nanoshells and 1.89 eV for CuO ellipsoids. For the contact-angle measurements, the wettability changed from hydrophilicity (18 degrees) to hydrophobicity (140 degrees) as the Cu2O nanoshells shifted to CuO ellipsoids.     

Shell model calculations of the adsorption and diffusion of K, Cl, and KCl on KCl(0 0 1)

Equilibrium adsorption positions and diffusion pathways of the ions K⁺ and Cl⁻ as well as of the molecule KCl on the terrace of the (0 0 1) surface of KCl were determined by shell model calculations allowing relaxations of the crystal lattice in the vicinity of the adsorbed species. For the ions each one adsorption position was found, in which the ions are located above the hollow site at the center of a slightly distorted square formed by two cations and two anions of the uppermost surface layer of the KCl crystal. Adsorption energies of −1.52 eV for K⁺ and −1.61 eV for Cl⁻ were calculated. Jumps of the ions occur from these positions to adjacent hollow positions in the ±[1 0 0] and ±[0 1 0] directions with a jump distance of a₀/2. The activation energies for the jumps result as 0.142 for K⁺ and 0.152 eV for Cl⁻ and the mean diffusion lengths as and . For the KCl molecule four distinct adsorption minima with energies between −0.932 and −0.825 eV were found. Because of the smaller lattice relaxation caused by the molecule the adsorption energies are considerably lower than for the single ions. In the position with the largest adsorption energy the ions of the admolecule are again placed above adjacent hollow sites. In two more adsorption positions only one ion is at the hollow site and the other one in a top position above an oppositely charged ion of the surface. In the fourth position with the smallest adsorption energy both ions are in top positions. Jumps between the different adsorption positions proceed by rotations of the molecule, in which one of its ions remains essentially attached to a local minimum position. The diffusion and desorption of a KCl molecule was studied by a Monte Carlo method, resulting in a mean diffusion length x_s (nm) = 0.39 exp[0.84 (eV)/2kT], which agrees rather well with an experimental value of . Values for the mean stay time as well as for the surface diffusion coefficient are derived.     

Mixed Platinum(II) Halide Complexes with Sulfur Donors

Abstract

The reaction of platinum(II) halides with stoichiometric amounts of either dimethyl sulfoxide (DMSO) or thiocarbamic ester (L) in acetone yields the complexes cis-[Pt(L)(DMSO)X₂], where L α MTC (EtOSCNHMe), ETC (EtOSCNHEt) or TC (EtOSCNH₂) and X α Cl or Br. The compounds have been isolated and characterized by elemental analysis and by infrared and nmr (¹H and ¹³C) spectroscopy. Either dimethyl sulfoxide or thiocarbamic ester coordinate through the sulphur atom. In the MTC and ETC adducts the planar ligand molecule is present in the isomeric form bearing the N-alkyl group in an anti position with respect to the thiocarbonyl group.     

Nickel-Catalysed Reactions of Allyl Halides and Related Compounds

Allyl compounds react with carbon monoxide, or with carbon monoxide and acetylene, in the presence of tetracarbonylnickel as catalyst. These catalysts are involved also in coupling reactions and addition reactions of activated olefins and ketones. Reactions of this type can be used for the preparation of unsaturated aliphatic acids, esters, nitriles, hydrocarbons, alicyclic ketones, keto acids, keto esters, diketones, lactones, phenols, and other compounds. The reactions proceed via π-allylnickel complexes.     

A simple catalyst system for the palladium-catalyzed coupling of aryl halides with terminal alkynes

A convenient catalyst system consisting of Pd(OAc)₂, PPh₃, K₃PO₄ and DMSO was found to be effective for the coupling reaction of aryl halides with terminal alkynes as well as the deacetonative coupling reaction using a 4-aryl-2-methylbut-3-yn-2-ol as a terminal alkyne precursor. An iminophosphine as a ligand worked more effectively for some combination of substrates than triphenylphosphine.     

X-ray diffraction and colour centre studies on RbCl-RbBr mixed crystals

X-ray diffraction and colour centre studies have been carried out on RbCl-RbBr mixed crystals. The lattice constant closely follows the linear form of Vegard’s law. The mean Debye-Waller factor shows a highly nonlinear composition dependence. The composition dependence of the F-band peak position is slightly nonlinear but that of the F-band half-width is highly nonlinear. The Ivey-Mollow relation holds for this system with an index of 2.5. The ‘size effect’ is found to have a dominant effect on the F-band width.     

微波作用下由苯亚磺酸钠烃基化合成砜

微波照射下苯亚磺酸钠与卤代烃作用，可以较高的产率生成相应的砜，反应速度大大加快，反应时间可缩短到2～7min。     

Enhanced surface atomic step motion observed in real time after nanoindentation of NaCl(100)

The nanometer-scale indentation of a crystalline surface produces nanostructures that evolve on a timescale that is inaccessible to existing imaging methods for the vast majority of surfaces. We have been able to observe the dynamic evolution of the freshly cleaved surface of a NaCl(100) crystal after indentation with an atomic force microscope (AFM) in air. Here we present sequential AFM images featuring vertical atomic resolution which show that atomic terrace motion is greatly enhanced by the AFM indentation. Moreover, some of the nanometric features generated by the indentation become reassimilated into the crystalline surface structure of the surroundings of the indentation over a period of time of the order of several minutes.     

Axial energy distributions of Li and F desorbed from LiF surfaces by fast ion impact

Initial axial kinetic energy (E_z) distributions of Li⁺ and F⁻ secondary ions desorbed from LiF surfaces, bombarded by low current (500 particles/s) N³⁺ beams in the 0.075–7.5 MeV primary ion energy (E_PI) range, were measured by using the time-of-flight technique. In this energy range, the electronic energy loss, S_e, increases from 25 to 160 eV/Å, while the nuclear stopping power, S_n, decreases from 8.0 to 0.25 eV/Å. The observed F⁻ initial axial kinetic energy distribution can be described by the linear collision cascade theory and no other contribution was found. The F⁻ total yield decreases proportionally to S_n. The Li⁺ distribution presents a remarkable deviation from the cascade prediction, indicating the existence of additional mechanisms related to the electronic energy-loss process. For the range of E_PI studied, these mechanisms produce a Li⁺ energy distribution with a Maxwell-Boltzman-like shape, which vanishes above E_z 10 eV and presents a maximum at E_z 1.2 eV. The Li⁺ yield is nonlinear with the electronic energy loss, S_e. A simple desorption model, based on the spatial distribution of the energy deposited by the projectile and on the effective energy-loss concept, is presented. This spatial distribution of the deposited energy is due to secondary electron cascades and is connected with a ESD-like mechanism on the surface.