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Copper(II) coordination polymers, [Cu(μ2‐HL)]n⋅n(CH3)2C=O (1), [Cu(μ1‐HL)(CH3OH)]n (2) and [Cu(μ1‐HL)(H2O)]n (3) were isolated by recrystallization (in acetone, methanol and dimethylformamide, respectively) of an intermediate produced by a solid state ball milling reaction of CuCl2⋅2H2O with 2‐(2‐(1,3‐dioxo‐1‐(phenylamino)butan‐2‐ylidene)hydrazinyl)benzoic acid (H3L). Reaction under conventional fully solution‐based conditions of CuCl2⋅2H2O with H3L in acetone and dimethylformamide leads to 3, and in methanol to the known monomeric compound [Cu(HL1)(H2O)(CH3OH)] (4). All the coordination polymers 1−3 act as homogenous catalysts for the peroxidative (H2O2) oxidation of acetone to acetic acid with yields up to 50% and at room temperature. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a set of iron(III) complexes, viz. the mononuclear [Fe(L)3] (1) and [NHEt3][Fe(L)2(Cl)2] (2), the dinuclear methoxido-bridged [Fe(L)2(μ-OMe)]2.DMF.1.5MeOH (3), and the heteronuclear Fe(III)/Na(I) two-dimensional coordination polymer [Fe(N3)(μ-L)2(μ-O)1/2(Na)(μ-H2O)1/2]n (4), are reported. Reactions of 3-amino-2-pyrazinecarboxylic acid (HL) with iron(III) chloride under different reaction conditions were studied, and the obtained compounds were characterized by elemental analysis, Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray single-crystal diffraction. Compound 1 is a neutral mononuclear complex, whereas 2 is mono-anionic with its charge being neutralized by triethylammonium cation. Compounds 3 and 4 display a di-methoxido-bridged dinuclear complex and a two-dimensional heterometallic Fe(III)/Na(I) polynuclear coordination polymer, respectively. Compounds 3 and 4 are the first examples of methoxido- and oxido-bridged iron(III) complexes, respectively, with 3-amino-2-pyrazinecarboxylate ligands. The electrochemical study of these compounds reveals a facile single-electron reversible Fe(III)-to-Fe(II) reduction at a positive potential of 0.08V vs. saturated calomel electrode (SCE), which is in line with their ability to act as efficient oxidants and heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation (with tert-butyl hydroperoxide) of cyclohexanol to cyclohexanone (almost quantitative yields after 1 h). Moreover, the catalysts are easily recovered and reused for five consecutive cycles, maintaining a high activity and selectivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • New copper(I) C-scorpionate compounds are synthesized and characterized. • Low-power microwave-assisted three component cycloaddition reaction in aq medium. • Catalytic system highly efficient under mild reducing agent-free conditions. Abstract Reactions of CuX (X = Br or I) and [Cu(MeCN) 4 ][BF 4 ] with the neutral C-scorpionates HC(3,5-Me 2 pz) 3 and HC(3-Phpz) 3 (Tpm∗ and TpmPh, respectively) proceed readily at room temperature to give the neutral copper(I) complexes [CuBr(TpmPh)] (1), [CuI(TpmPh)] (2), [CuBr(Tpm∗)] (3), [CuI(Tpm∗)] (4) and the cationic [Cu(TpmPh)(NCMe)][BF 4 ] (5), [Cu(Tpm∗)(NCMe)][BF 4 ] (6) and [Cu(Tpm∗) 2 ][BF 4 ] 2 (7), the latter also obtained from 6 after some time in air. Compounds 1 – 7 act as homogeneous catalysts for the low-power microwave-assisted three component (alkyne, bromobenzyl, sodium azide) cycloaddition reaction (CuAAC) to afford 1,4-disubstituted-1,2,3-triazoles, with 7 as the best catalyst. The catalytic reaction evolves well in ROH/H 2 O solution, depends on the R group and proceeds better when R = Me, here achieving yields up to 94%. The alcohol plays a role in the Cu(II)-to-Cu(I) Glaser-type induction period, therefore avoiding a reducing agent in the system. [ABSTRACT FROM AUTHOR]

A survey of the electrochemical properties of homoscorpionate tris(pyrazol-1-yl)methane complexes is presented. The relationship between structural features and catalytic efficiency toward the oxidative functionalization of inexpensive and abundant raw-materials to added-value products is also addressed. [ABSTRACT FROM AUTHOR]

For the first time, microwave (MW) irradiation was successfully applied to peroxidative cyclohexane oxidation catalyzed by a C-scorpionate complex, [FeCl2(Tpm)] (1; Tpm = hydrotris(pyrazol-1-yl)methane), providing a highly selective and fast eco-friendly procedure to produce a KA (cyclohexanol + cyclohexanone) oil mixture (up to ca. 100% selectivity) with 28% yield in 1 h at 50 °C in MeCN. Water, organics, and ionic liquids (ILs, [bmim][N(CN)2] and [bmim][BF4]) were used as solvents, and their interactions with 1 were determined by DFT calculations. The possibility to recycle and reuse 1 (up to nine consecutive cycles) without loss of activity is also observed for the IL [bmim][BF4]. Moreover, higher catalytic activities under additive-free conditions are obtained with the ILs in comparison to those with the other solvents. Tuning the alcohol/ketone selectivity is also possible by choosing the appropriate IL solvent. [ABSTRACT FROM AUTHOR]

The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) with a copper(II) salt of a base of a strong acid, i.e., nitrate, chloride or sulphate, yielded the mononuclear complexes [Cu(H2L)(NO3)(H2O)] (1), [Cu(H2L)Cl]μ2MeOH (2) and the binuclear complex [{Cu(H2L)} 2 (μ-SO4)]μ2MeOH (3), respectively, with H2Lμ in the keto form. Compounds 1-3 were characterized by elemental analysis, Infrared (IR) spectroscopy, Electrospray IonisationMass Spectrometry (ESI-MS) and single crystal X-ray crystallography. All compounds act as efficient catalysts towards the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, under mild conditions. In the presence of an acid promoter, overall yields (based on the alkane) up to 25% and a turnover number (TON) of 250 (TOF of 42 h-1) after 6 h, were achieved. [ABSTRACT FROM AUTHOR]

The iron(III) complexes [H(EtOH)][FeCl(L)] ( 1), [Hbipy][FeCl(L)].DMF ( 2) and [FeCl(L)(2,2′-bipy)] ( 3) (L = 3-amino-2-pyrazinecarboxylate; Hbipy = doubly protonated 4,4′-bipyridine; 2,2′-bipy = 2,2′-bipyridine, DMF = dimethylformamide) have been synthesized and fully characterized by IR, elemental and single-crystal X-ray diffraction analyses, as well as by electrochemical methods. Complexes 1 and 2 have similar mononuclear structures containing different guest molecules (protonated ethanol for 1 and doubly protonated 4,4′-bipyridine for 2) in their lattices, whereas the complex 3 has one 3-amino-2-pyrazinecarboxylate and a 2,2′-bipyridine ligand. They show a high catalytic activity for the low power (10 W) solvent-free microwave assisted peroxidative oxidation of 1-phenylethanol, leading, in the presence of TEMPO, to quantitative yields of acetophenone [TOFs up to 8.1 × 10 h, ( 3)] after 1 h. Moreover, the catalysts are of easy recovery and reused, at least for four consecutive cycles, maintaining 83 % of the initial activity and concomitant rather high selectivity. Graphical Abstract: 3-Amino-2-pyrazinecarboxylic acid is used to synthesize three new iron(III) complexes which act as heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation of 1-phenylethanol. [InlineMediaObject not available: see fulltext.] [ABSTRACT FROM AUTHOR]

One-pot template condensation of CCl3C≡N with ammonia on a metal source [MnCl2·4H2O, FeCl3·6H2O or Co(CH3COO)2·4H2O] in DMSO led to the formation of tris{2,4-bis(trichloromethyl)-1,3,5-triazapentadienato}-M(iii) complexes, [M{NH=C(CCl3)NC(CCl3)=NH}3]·n(CH3)2SO [M = Mn, n = 1 (1); M = Fe, n = 2 (2); M = Co, n = 2 (3)], which were characterized using elemental analysis, and IR, ESI-MS and single-crystal X-ray analysis. The role of inter- and intramolecular non-covalent halogen and hydrogen bonds in the synthesis of 1–3 is discussed. It is shown that the crystal ionic radii of the metal ions [68.5 (Co) ＜ 69 (Fe) ＜ 72 (Mn), pm] are related to the corresponding Cl…Cl distances [3.178 (3) ＞ 3.155 (2) ＞ 3.133 (1) Å]. Compounds 1–3 and the related di(triazapentadienato)-Cu(ii) complex [Cu{NH=C(CCl3)NC(CCl3)=NH}2]·2(CH3)2SO (4) act as catalyst precursors for the additive-free microwave (MW) assisted homogeneous oxidation of 1-phenylethanol with tert-butylhydroperoxide (TBHP), leading to the formation of acetophenone with yields up to 99% and TONs up to 5.0 × 103 after 1 h of low power (10 W) MW irradiation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The in situ spectroelectrochemical cyclic voltammetric studies of the antimony-monocapped nickel(II) and iron(II) tris-pyridineoximates with a labile triethylantimony cross-linking group and Zr(IV)/Hf(IV) phthalocyaninate complexes were performed in order to understand the nature of the redox events in the molecules of heterodinuclear zirconium(IV) and hafnium(IV) phthalocyaninate-capped derivatives. Electronic structures of their 1e-oxidized and 1e-electron-reduced forms were experimentally studied by electron paramagnetic resonance (EPR) spectroscopy and UV−vis−near-IR spectroelectrochemical experiments and supported by density functional theory (DFT) calculations. The investigated hybrid molecular systems that combine a transition metal (pseudo)clathrochelate and a Zr/Hf-phthalocyaninate moiety exhibit quite rich redox activity both in the cathodic and in the anodic region. These binuclear compounds and their precursors were tested as potential catalysts in oxidation reactions of cyclohexane and the results are discussed. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the catalytic activity of hybrid materials of iron supported on hierarchical zeolites in the oxidation reaction of 1-phenylethanol to acetophenone. A greener approach was considered for the preparation of the catalyst and performance of the oxidation reaction. Hierarchical BEA zeolite samples were obtained from an alkaline and a subsequent acid treatment. The materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen adsorption at −196 °C. An iron salt was incorporated onto the hierarchical zeolites by mechanochemical grinding and the catalytic performance of the prepared materials was evaluated towards the microwave assisted oxidation reaction of 1-phenylethanol. The catalyst obtained by Fe immobilization on sample modified by 0.2 M NaOH followed by acid treatment (Fe@BEA0.2AT) is the most promising material with 35% yield and 56% selectivity to acetophenone, allowing five reuse cycles without significant loss of activity and selectivity. [ABSTRACT FROM AUTHOR]

A new hexa-nuclear Cu(II) complex [Cu3(μ2-1κNO2,2κNO2-L)(μ-Cl)2(Cl)(MeOH)(DMF)2]2 (1), where H4L = N′1,N′2-bis(2-hydroxybenzylidene)oxalohydrazide, was synthesized and fully characterized by IR spectroscopy, ESI-MS, elemental analysis, and single crystal X-ray diffraction. Complex 1 and the dinuclear oxidovanadium(V) one [{VO(OEt)(EtOH)}2(1κNO2,2κNO2-L)]·2H2O (2) were used as catalyst precursors for the neat oxidation of primary (cinnamyl alcohol) and secondary (1-phenyl ethanol, benzhydrol) benzyl alcohols and of the secondary aliphatic alcohol cyclohexanol, under microwave irradiation using tert-butyl hydroperoxide (TBHP) as oxidant. Oxidations proceed via radical mechanisms. The copper(II) compound 1 exhibited higher catalytic activity than the vanadium(V) complex 2 for all the tested alcohol substrates. The highest conversion was found for 1-phenylethanol, yielding 95.3% of acetophenone in the presence of 1 and in solvent and promoter-free conditions. This new Cu(II) complex was found to exhibit higher activity under milder reaction conditions than the reported aroylhydrazone Cu(II) analogues. [ABSTRACT FROM AUTHOR]

The mononuclear Cu(II) complex [Cu((kNN′O-HL)(H2O)2] (1) was synthesized using N-acetylpyrazine-2-carbohydrazide (H2L) and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray crystallography. Two Fe(III) complexes derived from the same ligand viz, mononuclear [Fe((kNN′O-HL)Cl2] (2) and the binuclear [Fe(kNN′O-HL)Cl(μ-OMe)]2 (3) (synthesized as reported earlier), were also used in this study. The catalytic activity of these three complexes (1–3) was examined towards the oxidation of alcohols using tert-butyl hydroperoxide (TBHP) as oxidising agent under solvent-free microwave irradiation conditions. Primary and secondary benzyl alcohols (benzyl alcohol and 1-phenylethanol), and secondary aliphatic alcohols (cyclohexanol) were used as model substrates for this study. A comparison of their catalytic efficiency was performed. Complex 1 exhibited the highest activity in the presence of TEMPO as promoter for the oxidation of 1-phenylethanol with a maximum yield of 91.3% of acetophenone. [ABSTRACT FROM AUTHOR]

The catalytic activity of the water-soluble scorpionate coordination compounds [Cu(κ-NN′O-Tpms)2] (1), [Mn(Tpms)2] (2) and Li[FeCl2(κ-NN′N″-Tpms)] (3) [Tpms = tris(pyrazolyl)-methane sulfonate, O3SC(pz)3−], were studied towards the (Henry) reaction between benzaldehyde and nitromethane or nitroethane in aqueous medium to afford, respectively, 2-nitro-1-phenylethanol or 2-nitro-1-phenylpropanol, the latter in the syn and the anti diastereoisomeric forms. Complex 1 exhibited the highest activity under the optimum experimental conditions and was used to broaden the scope of the reaction to include several aromatic aldehydes achieving yields up to 94%. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) polynuclear Cu(II) complex (1) derived from (5-bromo-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H2L) is synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS, and single crystal X-ray crystallography. Its catalytic performance towards the solvent-free microwave-assisted peroxidative oxidation of aliphatic and aromatic hydrocarbons under mild conditions is compared with that of dinuclear Cu(II) complexes (2 and 3) of the same ligand, previously reported as antiproliferative agents. Polymer 1 exhibits the highest activity, either for the oxidation of cyclohexane (leading to overall yields, based on the alkane, of up to 39% of cyclohexanol and cyclohexanone) or towards the oxidation of toluene (selectively affording benzaldehyde up to a 44% yield), after 2 or 2.5 h of irradiation at 80 or 50 °C, respectively. [ABSTRACT FROM AUTHOR]

Abstract A microwave-assisted protocol to selectively produce benzaldehyde from neat styrene was developed by using ferrite magnetic nanoparticles, MFe 2 O 4 [M = Mn2+, Fe2+, Co2+, Ni2+, Cu2+ or Zn2+] as catalysts. The CoFe 2 O 4 nanoparticles revealed the best catalytic performance towards the selective production of benzaldehyde (93% selectivity at 86% styrene conversion) in 3 h at 80 °C using t -BuOOH as oxidant. The catalyst can be readily isolated by using an external magnet, and no significant loss of activity is observed when reused up to 5 consecutive runs. The low E -factor (mass ratio of waste to desired product) value (2.5) is indicative of the eco-friendly nature of the present catalytic system. Graphical abstract Unlabelled Image Highlights • Novel, eco-friendly benzaldehyde synthesis • Ferrite nanoparticles able to catalyze styrene oxidation. • Nanocatalytic systems using low catalyst loading, mild and solvent-free conditions. • Reusable stable magnetic metal-transition ferrite nanocatalysts [ABSTRACT FROM AUTHOR]

Reaction of a new hydrazone of β-diketone, 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)isophthalic acid (H 3 L), with zinc(II) nitrate hexahydrate in a mixture of DMF and water (1:1) under hydrothermal conditions affords the 1D coordination polymer [Zn( μ 3 -HL)(H 2 O) 2 ] n ∙ nH 2 O ( 1 ), where one of the carboxylic groups links two Zn(II) centers in a bridging bidentate ( syn-syn -type) mode and the remaining one ligates a third metal cation in a monodentate fashion. It was characterized by IR and NMR spectroscopies, ESI-MS, elemental and single-crystal X-ray crystal structural analyses. 1 acts as an efficient pre-catalyst for the Henry reaction at 40 °C in aqueous medium, providing β-nitroalcohols with good yields (67–86%) and diastereoselectivities ( syn:anti 77:23–69:31). [ABSTRACT FROM AUTHOR]