Celebratory Symposium A – Catalysis and the Periodic Table Selected Metal Catalysts Spanned over the Periodic Table Towards Alkane Functionalization

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Celebration of the Periodic Table of the Elements at the Academy of Sciences of Lisbon. A Chemistry Symposium

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Elogio histórico do académico João José Rodiles Fraústo da Silva proferido pelo académico Armando J. L. Pombeiro

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Highly active and selective supported rhenium catalysts for aerobic oxidation of n-Hexane and n-Heptane

A series of derivative C-scorpionate rhenium complexes, i.e., [ReCl2{NNC(O)C6H5} (Hpz)(PPh3)2] (A) (where Hpz is pyrazole), [ReCl2{NNC(O)C6H5}(Hpz)2(PPh3)] (B), [ReClF {NNC(O)C6H5}(Hpz)2(PPh3)] (C), and their precursor [ReOCl3(PPh3)2] (D), immobilized on 3-aminopropyl-functionalized silica have been prepared and used for neat O2 oxidation of n-hexane and n-heptane mainly to the corresponding alcohols and, in lower amounts, ketones. The supported catalyst C, with fluoro- and diazenido-ligands, exhibits the highest activity for both alkanes (overall turnover numbers (TONs) up to 3.8 _ 103 and 2.5 _ 103, for n-hexane and n-heptane, respectively) and can be reused in consecutive catalytic cycles. Improved conversion was observed after addition of hetero-carboxylate co-catalysts. A free-radical-based mechanism is proposed to explain the product formation.info:eu-repo/semantics/publishedVersio

Elogio histórico do académico António Herculano Guimarães Chaves de Carvalho proferido pelo académico Armando Pombeiro

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Oxorhenium complexes bearing the water-soluble tris(pyrazol-1-yl)methanesulfonate, 1,3,5-triaza-7-phosphaadamantane, or related ligands, as catalysts for baeyer-villiger oxidation of ketones

New rhenium(VII or III) complexes [ReO3(PTA)(2)][ReO4] (1) (PTA = 1,3,5-triaza-7-phosphaadamantane), [ReO3(mPTA)][ReO4] (2) (mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane cation), [ReO3(HMT)(2)] [ReO4] (3) (HMT = hexamethylenetetramine), [ReO3(eta(2)-Tpm)(PTA)][ReO4] (4) [Tpm = hydrotris(pyrazol-1-yl)methane, HC(pz)(3), pz = pyrazolyl), [ReO3(Hpz)(HMT)][ReO4] (5) (Hpz = pyrazole), [ReO(Tpms)(HMT)] (6) [Tpms = tris(pyrazol-1-yl)methanesulfonate, O3SC(pz)(3)(-)] and [ReCl2{N2C(O)Ph} (PTA)(3)] (7) have been prepared from the Re(VII) oxide Re2O2 (1-6) or, in the case of 7, by ligand exchange from the benzoyldiazenido complex [ReCl2(N2C-(O)Ph}(Hpz)(PPh3)(2)], and characterized by IR and NMR spectroscopies, elemental analysis and electrochemical properties. Theoretical calculations at the density functional theory (DFT) level of theory indicated that the coordination of PTA to both Re(III) and Re(VII) centers by the P atom is preferable compared to the coordination by the N atom. This is interpreted in terms of the Re-PTA bond energy and hard-soft acid-base theory. The oxo-rhenium complexes 1-6 act as selective catalysts for the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g., 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone, and 3,3-dimethyl-2-butanone or pinacolone) to the corresponding lactones or esters, in the presence of aqueous H2O2. The effects of a variety of factors are studied toward the optimization of the process

Efficient cyclohexane oxidation with hydrogen peroxide catalysed by a C-scorpionate iron(II) complex immobilized on desilicated MOR zeolite

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

Greener Selective Cycloalkane Oxidations with Hydrogen Peroxide Catalyzed by Copper-5-(4-pyridyl)tetrazolate Metal-Organic Frameworks

Microwave assisted synthesis of the Cu(I) compound [Cu(µ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2]n∙(DMF)2n (2) and [Cu(µ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h−1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1–3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity

Greener Selective Cycloalkane Oxidations with Hydrogen Peroxide Catalyzed by Copper-5-(4-pyridyl)tetrazolate Metal-Organic Frameworks

Microwave assisted synthesis of the Cu(I) compound [Cu(µ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2]n∙(DMF)2n (2) and [Cu(µ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h−1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1–3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity

The solvation and redox behavior of mixed ligand copper(II) complexes of acetylacetonate and aromatic diimines in ionic liquids

The behavior of two cationic copper complexes of acetylacetonate and 2,2'-bipyridine or 1,10-phenanthroline, [Cu(acac)(bipy)]Cl (1) and [Cu(acac)(phen)]Cl (2), in organic solvents and ionic liquids, was studied by spectroscopic and electrochemical techniques. Both complexes showed solvatochromism in ionic liquids although no correlation with solvent parameters could be obtained. By EPR spectroscopy rhombic spectra with well-resolved superhyperfine structure were obtained in most ionic liquids. The spin Hamiltonian parameters suggest a square pyramidal geometry with coordination of the ionic liquid anion. The redox properties of the complexes were investigated by cyclic voltammetry at a Pt electrode (d = 1 mm) in bmimBF(4) and bmimNTf(2) ionic liquids. Both complexes 1 and 2 are electrochemically reduced in these ionic media at more negative potentials than when using organic solvents. This is in agreement with the EPR characterization, which shows lower A(z) and higher g(z) values for the complexes dissolved in ionic liquids, than in organic solvents, due to higher electron density at the copper center. The anion basicity order obtained by EPR is NTf2-, N(CN)(2)(-), MeSO4- and Me2PO4-, which agrees with previous determinations. (C) 2013 Elsevier B.V. All rights reserved