Catalytic epoxidation of olefin over supramolecular compounds of molybdenum oxide clusters and a copper complex

The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu（bipy）]4[Mo15O47].2H2O （1） and [Cu1（bix）][（Cu1bix） （δ-MoVl8O26）0.5] （2） （bipy = 4,4＇-bipyridine, bix = 1,4-bis（imidazole-1-ylmethyl）benzene）. Both compounds were catalytically active and stable for the epoxidation of cyclooctene, 1-octene, and styrene with tert-butyl hydroperoxide （t-BuOOH） as oxidant. The excellent catalytic performance was attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex, which resulted in the formation of easily accessible Mo species with high electropositivity. In addition, the copper complex also acted as an active site for the activation of t-BuOOH, thus im- proving these copper complex-modified polyoxometalates.

Ultrasmall AU10 clusters anchored on pyramid-capped rectangular TiO2 for olefin oxidation

UltrasmaU Au10 clusters have a unique electronic structure and can act as a charge reservoir to donate electrons or accept charges. This is particularly important for catalysis, since it leads to facile charge transfer across the interface between the gold species and the oxide substrate. To determine the electronic and structural effects of Au10 on the catalytic oxidation, a TiO2 charge carrier was chosen as the substrate to anchor Au10 for olefin oxidation. Au10 supported on TiO2-RP （RP = pyramid-capped columnar structure） exhibited superior catalytic activity to Au10/TiO2 nanotubes and Au10/P25. In addition, the supported Au10 clusters gave rise to higher activity than supported Au20, Au144 clusters, and 5 nm Au nanocrystals. The superior catalytic ability of Au^0fFiO2-RP arises from the charge/discharge effect of the Au10/TiO2-RP interface, which effectively improves the formation of active oxygen species on electron-rich gold atoms at the terminal position of Au10, and promotes the activation of olefin C--C bonds on the electron-deficient gold atoms of Au10.

Water-based synthesis of nanoscale hierarchical metal-organic frameworks:Boosting adsorption and catalytic performance

The combination of nano sizes,large pore sizes and green synthesis is recognized as one of the most crucial and challenging problems in constructing metal-organic frameworks(MOFs).Herein,a water-based strategy is proposed for the synthesis of nanoscale hierarchical MOFs(NH-MOFs)with high crystallinity and excellent stability.This approach allows the morphology and porosity of MOFs to be fine tuned,thereby enabling the nanoscale crystal generation and a well-defined hierarchical system.The aqueous solution facilitates rapid nucleation kinetics,and the introduced modulator acts as a deprotonation agent to accelerate the deprotonation of the organic ligand as well as a structure-directing agent(SDA)to guide the formation of hierarchical networks.The assynthesized NH-MOFs(NH-ZIF-67)were assessed as efficient adsorbents and heterogeneous catalysts to facilitate the diffusion of guest molecules,outperforming the parent microZIF-67.This study focuses on understanding the NH-MOF growth rules,which could allow tailor-designing NH-MOFs for various functions.

The reaction of perfluoroalkanesulfinatesIV.Perfluoroalkyl radical addition to olefins initiated by single electron oxidation of perfluoroalkanesulfinate

Sodium perfluoroalkanesulfinates [Cl(CF_2)n SO_2 Na (1), a, n=4; b, n=6; c, n=8] with the reduction potentials about 0.95-1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)_3·2H_2O, Ce(SO_4)_2, HgSO_4 and Co_2O_3 to generate perfluoroalkyl radicals which added to the olefins RCH=CHR′to give two kinds of adducts, namely RCH (R_f) CHXR′(3, X=H; 4, X=OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.

Preparation of some new arylseleno compounds and application in the oxidation of olefins

Fifteen pyridine and substituted benzene diselenides,seleninic acids and seleninic anhydrides have been synthesized.Among them,4,4'-dipyridinediselenide,bis(2,4-dimethoxyphenyl)diselenide, 2,4-dimethoxyphenyl seleninic acid,2-pyridineseleninic acid,2-pyridineseleninic anhydride,4-pyridine- seleninic anhydride,2-nitrophenyl seleninic anhydride and 4-nitrophenyl seleninic anhydride were new compounds.Their regioselective oxidation or dehydrogenation of β-pinene,3β-benzoyloxycholest- 5-ene and androstan-3-one have been studied and compared.2-Pyridineseleninic anhydride is a more efficient oxidant than the others;most of the substituted benzeneseleno derivatives did not give the expected products.

Theoretical investigation on the elusive biomimetic iron(Ⅲ)-iodosylarene chemistry: An unusual hydride transfer triggers the Ritter reaction

Introduction of iodosylarnes into biomimetic nonheme chemistry has made great achievement on identification of the subtle metal-oxygen reaction intermediates. However, after more than three decades of experimental and theoretical efforts the nature of the metal-iodosylarene adducts and the related dichotomous one-oxidant/multiple-oxident controversy have remained a matter of speculation. Herein, we report a theoretical study of the structure-activity relationship of the noted iron(Ⅲ)-iodsylarene complex,FeⅢ(Ph IO)(OTf)3(1), in oxygenation of cyclohexene. The calculated results revealed that 1 behaves like a chameleon by adapting its roles as a 2 e-oxidant or an oxygen donor, as a response to the regioselective attack of the C–H bond and the C=C bond. The oxidative C–H bond activation by 1 was found, for the first time, to proceed via a novel hydride transfer process to form a cyclohexene carbonium intermediate,such non-rebound step triggers the Ritter reaction to uptake an acetonitrile molecule to form the amide product, or proceeds with the rebound of the hydroxyl group return to the solvent cage to form the hydroxylated product. While in the C=C bond activation, 1 is a normal oxygen donor and shows two-state reactivity to present the epoxide product via a direct oxygen atom transfer mechanism. These mechanistic findings fit and explain the famous Valentine’s experiments and enrich the non-rebound scenario in bioinorganic chemistry.