Abstract:The new half-sandwich scorpionate complexes [hydridotris(1-pyrazolyl)methane]vanadium trichloride, ([VCl 3 {HC(pz) were synthesized, characterized and shown to act, as well as the related (tripyrazolylmethane)copper dichloride, [CuCl 2 {HC(pz) 3 }] 6, as selective catalysts (or catalyst precursors) for the peroxidative oxidation (with hydrogen peroxide) of cyclohexane to cyclohexanol and cyclohexanone, under mild conditions (at room temperature and using an aqueous solution of H 2 O 2 ). The iron complexes are the most active ones (reaching TON values up to ca. 690), the effects of a variety of factors are reported and the reaction is shown to proceed via both C-and O-centred radical mechanisms, conceivably involving a metal-based oxidant.

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Abstract:The hydrotris(pyrazol-1-yl)methane iron(II) complex [FeCl2{eta(3)-HC(pz)(3)}] (Fe, pz = pyrazol-1-yl) immobilized on commercial (MOR) or desilicated (MOR-D) zeolite, catalyses the oxidation of cyclohexane with hydrogen peroxide to cyclohexanol and cyclohexanone, under mild conditions. MOR-D/Fe (desilicated zeolite supported [FeCl2{eta(3)-HC(pz)(3)}] complex) provides an outstanding catalytic activity (TON up to 2.90 x 10(3)) with the concomitant overall yield of 38%, and can be easy recovered and reused. The MOR or MOR-D supported hydrotris(pyrazol-1-yl)methane iron(II) complex (MOR/Fe and MOR-D/Fe, respectively) was characterized by X-ray powder diffraction, ICP-AES, and TEM studies as well as by IR spectroscopy and N-2 adsorption at -196 degrees C. The catalytic operational conditions (e.g., reaction time, type and amount of oxidant, presence of acid and type of solvent) were optimized. (C) 2013 Elsevier B.V. All rights reserved.

The reactions between 4'-phenyl-terpyridine (L) and nitrate, acetate or chloride Cu(II) salts led to the formation of [Cu(NO3)2L] (1), [Cu(OCOCH3)2L]·CH2Cl2 (2·CH2Cl2) and [CuCl2L]·[Cu(Cl)(μ-Cl)L]2 (3), respectively. Upon dissolving 1 in mixtures of DMSO-MeOH or EtOH-DMF the compounds [Cu(H2O){OS(CH3)2}L](NO3)2 (4) and [Cu(HO)(CH3CH2OH)L](NO3) (5) were obtained, in this order. Reaction of 3 with AgSO3CF3 led to [CuCl(OSO2CF3)L] (6). The compounds were characterized by ESI-MS, IR, elemental analysis, electrochemical techniques and, for 2-6, also by single crystal X-ray diffraction. They undergo, by cyclic voltammetry, two single-electron irreversible reductions assigned to Cu(II) → Cu(I) and Cu(I) → Cu(0) and, for those of the same structural type, the reduction potential appears to correlate with the summation of the values of the Lever electrochemical EL ligand parameter, which is reported for the first time for copper complexes. Complexes 1-6 in combination with TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl radical) can exhibit a high catalytic activity, under mild conditions and in alkaline aqueous solution, for the aerobic oxidation of benzylic alcohols. Molar yields up to 94% (based on the alcohol) with TON values up to 320 were achieved after 22 h.

Coupling five rigid or flexible bis(pyrazolato)-based tectons with late transition metal ions allowed us to isolate 18 coordination polymers (CPs). As assessed by thermal analysis, all of them possess a remarkable thermal\ud stability, their decomposition temperatures lying in the range of 340−500 °C. As demonstrated by N2 adsorption measurements at 77 K, their Langmuir specific surface areas span the rather vast range of 135−1758 m2/g, in agreement with the porous or dense polymeric architectures retrieved by powder X-ray diffraction structure solution methods. Two representative families of CPs, built up with either rigid or flexible spacers, were tested as catalysts in (i) the microwave-assisted\ud solvent-free peroxidative oxidation of alcohols by t-BuOOH, and (ii) the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone by H2O2 in acetonitrile. Those CPs bearing the rigid spacer, concurrently possessing higher specific surface areas, are more active than the corresponding ones with the flexible spacer. Moreover, the two copper(I)-containing CPs investigated exhibit the highest efficiency in both reactions, leading selectively to a maximum product yield of 92% (and TON up to 1.5 × 103) in the oxidation of 1-phenylethanol and of 11% in the oxidation of cyclohexane, the latter value being higher than that granted by the current industrial process

Review: 330 refs.

Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl4 with polyphenols from tea extracts, which act as both reducing and capping agents. The obtained AuNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). They act as highly efficient catalysts in the reduction of various aromatic nitro compounds in aqueous solution. The effects of a variety of factors (e.g., reaction time, type and amount of reducing agent, shape, size, or amount of AuNPs) were studied towards the optimization of the processes. The total polyphenol content (TPC) was determined before and after the catalytic reaction and the results are discussed in terms of the tea extract percentage, the size of the AuNPs, and their catalytic activity. The reusability of the AuNP catalyst in the reduction of 4-nitrophenol was also tested. The reactions follow pseudo first-order kinetics.

Aroylhydrazone Fe(iii) and Co(iii) complexes of both keto and enol tautomeric forms of the ligand are reported and shown to catalyze the microwave-assisted solvent-free peroxidative oxidation (by TBHP) of primary and secondary alcohols.