Development of a well-defined silica-supported tungstenocarbyne complex as efficient heterogeneous catalyst for alkyne metathesis

The interaction of [W(C-tBu)(CH₂-tBu)(OAr)₂] (Ar = 2,6-iPr₂C₆H₃) (1), with the hydroxyl groups of a silica dehydroxylated at 700 °C leads to [(SiO)W(OAr)₂(C-tBu)] (2) which was characterized by IR, solid-state NMR and mass balance analysis. This well-defined surface species is an efficient catalyst for the metathesis of pent-2-yne.     

Combinatorial Chemistry in Heterogeneous Catalysis: A New Scientific Approach or “the King's New Clothes”?

The spectacular success in materials science of the application of combinatorial chemistry has raised the hope that it may eventually lead to a new scientific approach to catalyst development. This method is, within the constraints of heterogeneous catalysis, merely a potentially efficient tool to be used in rational catalyst development and should not be considered an independent novel strategy towards rational catalyst design.     

Production of High Temperatures in the Chemical Laboratory: Examples of Application in Lanthanoid Oxo-Chemistry

High-temperature reactions have always been a fascinating although difficult field of experimentation for the chemist. In the case of solid-state reactions the problems with apparatus increase exponentially with rising temperature, so that especially in this area of inorganic chemistry the modern techniques of producing high temperatures—from the solar furnace to the high-power CO₂ laser—have yielded new and interesting possibilities, particularly in the field of metastable high-temperature compounds.     

A Coordination Chemist's View of Surface Science

Structure, a necessary element for an understanding of chemistry, has not been precisely defined, in molecular detail, for the surface species formed at a solid-gas interface. Dramatic advances in theory, instruments and experimental procedures have now provided the surface scientists with an impressive arsenal of structural and electronic probes. Chemistry in the form of the classic displacement reaction can also provide an insight to the structure of surface compounds. In fact, many of the experimental procedures and systematics of the coordination and organometallic chemist can be effectively utilized in a complementary fashion with surface physics techniques to gain a more definitive picture of chemisorption states and or reactions at a surface.     

超分子高分子化学进展

综述了超分子高分子化学近年来的进展,着重介绍固相聚合和毛杆高分子等方面的最新研究成果及应用展望。对超分子高分子化学的主要研究方法也作了扼要的介绍。     

The electrochemically tuneable hydrogen bonding interactions between a phenanthrenequinone-functionalized self-assembled monolayer and a phenyl-urea terminated dendrimer

We report the application of electrochemistry to detect and modulate hydrogen bonding interactions between a phenanthrenequinone-functionalized self-assembled monolayer and a phenyl-urea terminated dendrimer.     

A comparative study of the thermal reactivities of some transition metal oxalates in selected atmospheres

A comparative investigation has been made of the nonisothermal, solid-state thermal decompositions of the oxalates of six divalent transition metals (cations: manganese, iron, cobalt, nickel, copper and zinc) in alternative flowing atmospheres, inert (N₂, CO₂), reducing (H₂) and oxidizing (air). Derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) response peak maxima, providing a measure of reaction temperatures, have been used to determine salt reactivities and thus to characterize the factors that control the relative stabilities of this set of chemically related reactants. Two trends were identified. Trend (1): in the inert and reducing atmospheres, the decomposition temperature (salt stability) increased with rise in enthalpy of formation of the divalent transition metal oxide, MO. It is concluded that the rupture of the cation-oxygen (oxalate) bond is the parameter that determines the stability of salts within this set. Trend (2): the diminution of decomposition temperatures from values for reactions in inert/reducing atmosphere to those for reactions in an oxidizing atmosphere increased with the difference in formation enthalpy between MO and the other participating oxide (MO_3/2 or MO_1/2). The change of cation valence tended to promote reaction, most decompositions in O₂ occurred at lower temperatures, but the magnitude of the effect varied considerably within this set of reactants. Observed variations in stoichiometric and kinetic characteristics with reaction conditions are discussed, together with the mechanisms of thermal decompositions of these solid oxalates.This approach to the elucidation of crystolysis reaction mechanisms emphasizes the value of comparative investigations within the group of chemically related reactants. Previous isothermal kinetic studies had been made for each of the reactants selected here. From these, much has been learned about the form of the (isothermal) solid-state yield-time curves, often interpreted to provide information about the geometry of interface development for the individual rate processes. However, identification of the controls of reactivity, reaction initiation (nucleation) and advance (nucleus growth), is much more difficult to characterize and less progress has been made towards elucidation of the interface chemistry. The trends of reactivity changes with salt compositions, identified here, offer a complementary approach to that provided by the study of single salts. Much of the recent literature on thermal decompositions of solids has been concerned with individual reactants, but many results and conclusions are not presented in the widest possible perspective. Comparisons between systematically related reactants are identified here as providing a chemical context for the elucidation of the chemical steps that participate in interface reactions. The article advocates the use of a more chemical approach in investigations of crystolysis (solid-state chemical) reactions.