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The commercial dichloro(2-pyridinecarboxylato)gold(III) complex (1), anchored on different carbon materials, is reported for the first time as a catalyst in the cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid. The reaction was carried out in the presence of CO and water, peroxodisulfate, at ca. 50 °C, with 1 in solution and anchored on carbon nanotubes, carbon xerogel or activated carbon, with three different surface chemistries: original forms (CNT, CX or AC, respectively), oxidized with HNO3 (-ox) or oxidized with HNO3 and subsequently treated with NaOH (-ox-Na). 1@CNT-ox-Na was the best catalyst, yielding up to 78% of cyclohexanecarboxylic with a selectivity of 99%. Recycling studies showed that the catalyst was stable up to 4 cycles, the first decrease (11%) on the hydrocarboxylation yield being observed on the 5th cycle. No leaching of gold was found into the solution. The hydrocarboxylation of other cycloalkanes (cyclopentane, cycloheptane and cyclooctane) was also tested in the best conditions found for cyclohexane, but the respective carboxylic acids were obtained in considerably lower yields, which can be explained by different stabilities of cycloalkyl radicals.

The new C-scorpionate Ni(II) complex [NiCl{κ3-HC(pz)3}]Cl (pz = pyrazol-1-yl) is the first nickel homoscorpionate tris(pyrazol-1-yl)methane type complex to be applied as catalyst for the Heck–Mizoroki C–C cross coupling. The microwave-assisted reaction of butyl acrylate and 4-halogeno-anisole was efficiently catalyzed by the above Ni(II) complex, in ionic liquid medium, yielding the C–C coupling product in good yields. The stability of [NiCl{κ3-HC(pz)3}]Cl in the ionic liquid allowed its recycling and re-use for several consecutive catalytic cycles with preserved activity.

The highly efficient eco-friendly synthesis of acetic acid (40% yield) directly from ethane is achieved by the unprecedented use of N-heterocyclic carbene (NHC) and N-heterocyclic oxo-carbene (NHOC) gold(I) catalysts in mild conditions. This is a selective and promising protocol to generate directly acetic acid from ethane, in comparison with the two most used methods: (i) the three-step, capital- and energy-intensive process based on the high-temperature conversion of methane to acetic acid, (ii) the current industrial methanol carbonylation processes, based in iridium and expensive rhodium catalysts. Green metrics determinations highlight the environmental advantages of the new ethane oxidation procedure. Comparison with previous reported published catalysts is performed to highlight the features of this remarkable protocol.

The transformation of biomass and the utilization of all the by products derived from chemical conversion of biomass resources is one of the most important challenges nowadays. The impact in society and the level of awareness that already exists inside and outside the scientific community, makes the challenge of improving conversion of biomass to commodities a hot topic. Glycerol, a by-product obtained from the biodiesel production, is a key player compound due to its chemical versatility. The possibility of being used as solvent, reagent, reducing agent (in the polyol method), and so forth, makes glycerol an extremely appealing commodity. When used within nanotechnology, namely combined with nanomaterials, its potential becomes even higher. This review summarizes the work developed by the scientific community, during the last five years, in the use of glycerol with nano oxides. The analysis goes from the simple role of solvent to the oxidation of glycerol by nano oxides.

In this review, the roles of room temperature ionic liquids (RTILs) and RTIL based solvent systems as proposed alternatives for conventional organic electrolyte solutions are described. Ionic liquids are introduced as well as the relevant properties for their use in electrochemistry (reduction of ohmic losses), such as diffusive molecular motion and ionic conductivity. We have restricted ourselves to provide a survey on the latest, most representative developments and progress made in the use of ionic liquids as electrolytes, in particular achieved by the cyclic voltammetry technique. Thus, the present review comprises literature from 2015 onward covering the different aspects of RTILs, from the knowledge of these media to the use of their properties for electrochemical processes. Out of the scope of this review are heat transfer applications, medical or biological applications, and multiphasic reactions.

The direct, one-pot oxidation of ethane to acetic acid was, for the first time, performed using a C-scorpionate complex anchored onto a magnetic core-shell support, the Fe3O4/TiO2/[FeCl2{&kappa, 3-HC(pz)3}] composite. This catalytic system, where the magnetic catalyst is easily recovered and reused, is highly selective to the acetic acid synthesis. The performed green metrics calculations highlight the &ldquo, greeness&rdquo, of the new ethane oxidation procedure.

UIDB/00100/2020 UIDP/00100/2020 LA/P/0056/2020 IST-ID/119/2018 SFRH/BD/146426/2019 CEEC-INST/00102/2018 UIDB/50006/2020 UIDP/50006/2020 Base-UIDB/50020/2020 Programmatic-UIDP/50020/2020 The single-pot efficient oxidation of ethane to acetic acid catalysed by Au(I) or Au(III) compounds, chlorotriphenylphosphinegold(I) (1), chlorotrimethylphosphinegold(I) (2), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidenegold(I) chloride (3), dichloro(2-pyridinecarboxylato)gold(III) (4), homogenous and supported on different carbon materials: activated carbon (AC), multi-walled carbon nanotubes (CNT) and carbon xerogel (CX), oxidised with nitric acid followed by treatment with NaOH (-ox-Na), is reported. The reactions were performed in water/acetonitrile. The materials were selective for the production of acetic acid, with no trace of by-products being detected. The best homogenous catalysts were complexes 2 and 3 which showed the highest ethane conversion and an acetic acid yield of ca. 21%, followed by 4 and 1. The heterogenised materials showed much better activity than the homogenous counterparts, with acetic acid yields up to 41.4% for 4@CNT-ox-Na, and remarkable selectivity (with acetic acid being the only product detected). The heterogenised catalysts with the best results were reused up to five cycles, with no significant loss of activity, and maintaining high selectivity for acetic acid. 4@CNT-ox-Na showed not only the best catalytic activity but also the best stability during the recycling runs. publishersversion published

The C-scorpionate iron(II) complexes [FeCl2{κ3-HC(pz)3}] (1) (pz = pyrazol-1-yl), Li[FeCl2{κ3-SO3C(pz)3}] (2) and the new [FeCl2{κ3-HOCH2C(pz)3}] (3) act as catalysts for the hydrocarboxylation of cyclohexane (with CO and H2O) to cyclohexanecarboxylic acid in a remarkable yield (up to 60%) and under mild conditions. The catalysts selectivity for the acid can be tuned by CO pressure, catalyst amount and reaction temperature. Complex [FeCl2{κ3-HC(pz)3}] (1) provides the most effective catalyst requiring low CO pressure. This work constitutes an unprecedented use of iron complexes as catalysts for the hydrocarboxylation of alkanes.

For the first time, a magnetic C-scorpionate catalyst was prepared from the iron(II) complex [FeCl2{_3-HC(pz)3}] (pz = pyrazol-1-yl) and ferrite, using the sustainable mechanochemical synthetic procedure. Its catalytic activity for the cyclohexane oxidation with tert-butyl hydroperoxide (TBHP) was evaluated in different conditions, namely under microwave irradiation and under the effect of an external magnetic field. The use of such magnetic conditions significantly shifted the catalyst alcohol/ketone selectivity, thus revealing a promising, easy new protocol for tuning selectivity in important catalytic processes. info:eu-repo/semantics/publishedVersion

The catalytic activity of the iron(II) C-scorpionate complexes [FeCl2{HC(pz)3}] 1 (pz = pyrazol-1-yl) and [FeCl2{HOCH2C(pz)3}] 2, and of their precursor FeCl2·2H2O 3, towards cyclohexane oxidation with tert-butyl hydroperoxide was evaluated and compared in different media: acetonitrile, ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP]), supercritical carbon dioxide (scCO2), and scCO2/[bmim][X] (X = PF6 or FAP) mixtures. The use of such alternative solvents led to efficient and selective protocols for the oxidation of cyclohexane. Moreover, tuning the alcohol/ketone selectivity was possible by choosing the suitable solvent.