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Pd(II) and Pt(II) composites with activated carbon (AC), graphene oxide, and multiwalled carbon nanotubes were prepared by ball milling and used as catalysts for the Suzuki-Miyaura reaction, under several energy inputs (mechanical grinding, conventional heating, and microwave irradiation). The catalytic composites were characterized by ICP-MS, BET, XPS analyses, TEM, and SEM. The average particle size of the prepared composites was estimated to be in the range of 6&ndash, 30 nm, while the loadings of Pd and Pt did not significantly affect the surface area of the AC support due to the tendency to agglomerate as observed by the TEM analysis. The Pd/AC composites exhibit high mechanochemical catalytic activity in cross-coupling of bromobenzene and phenylboronic acid with molar yields up to 80% with TON and TOF of 222 and 444 h&minus, 1, respectively, achieved with Pd(4.7 wt%)-AC catalyst under the liquid assisted grinding for 0.5 h at ambient conditions, using cyclohexene as an additive.

A series of phthalocyanine (Pc) complexes of general formula [M(Pc)] (M = Mg, V, Mn, Fe, Co, Ni, Cu, Zn) was tested as catalysts for functionalization of sp3 C H bonds, namely in the mild stereoselective oxidation of cyclic alkanes (isomers of dimethylcyclohexane and decahydronaphthalene) using peroxides as oxidants. A high catalytic activity (yield of products up to 75% based on the oxidant) and outstanding retention of stereoconfiguration of substrates (>95% for isomers of dimethylcyclohexane) was disclosed for the cobalt phthalocyanine catalyst [Co(Pc)] using m-chloroperbenzoic acid (m-CPBA) as oxidant and nitric acid as promoter. The phthalocyanine complexes other than Co are much less active with yields of products

A series of known metal complexes, [LaL2(NO3)(H2O)2]·5H2O (1), [Zn(μ-L)(NO3)(H2O)]n (2), {[Cd2(μ-HL)(μ-L)(NO3)3(H2O)]·H2O}n (3) and [Hg(μ-L)(N3)]n·nH2O (4), were synthesized from the corresponding metal salts and 2-pyridinecarboxaldehyde isonicotinoylhydrazone (HL), and demonstrated high activity and selectivity in the cyanosilylation of aldehydes. Although all the complexes are derived from the same HL hydrazone ligand, the catalytic activity of 1–4 is different and relates to the metal center and coordination environment, whereas complex 1 being the most effective homogeneous Lewis acid-base catalyst towards the synthesis of cyanohydrin trimethylsilyl ethers from both aliphatic and aromatic aldehydes with yields up to 96.3 % in 6 h in methanol solution and at room temperature. According to the proposed mechanism, both coordination and noncovalent interactions (hydrogen and tetrel bonds) play a significant role and account for the higher catalytic activity of complex 1.

Iron-containing particulate catalysts of 0.1&ndash, 1 &micro, m size were prepared by wet and ball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.

The new 1D copper(II) coordination polymers (CPs) [Cu(μ-L1)(H2O)]n (1, H2L1 = 2-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)benzoic acid) and [Cu(μ-H2L2)(H2O)]n (2, H4L2 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)terephthalic acid) and the known zwitterionic 1D CP [Cu2(H2O)2(μ-H2L3)(μ-L3)]n (3, H3L3 = 2-(2-(4,4-dimethyl-2,6-dioxocyclo-hexylidene)hydrazinyl)terephthalic acid) were synthesized and tested as homogeneous catalysts for cyanosilylation of a variety of aldehydes to the corresponding cyanohydrin trimethylsilyl ethers. Among these polymeric catalysts, 3, with a zwitterionic charater, is the most effective one, giving 86–99% yield of the ethers upon reaction of aliphatic and aromatic aldehydes with trimethylsilyl cyanide in methanol at room temperature in 4 h. Non-covalent interactions (cation-π and tetrel bondings) involving the aldehyde substrate are proposed to assist the cyanosilylation reaction.

Three new water-soluble copper(II) complexes [Cu(HL)(H2O){(CH3)2NCHO}] (1), [Cu(H2L)2(im)4]·CH3OH (2) and [Cu(HL)(CH3OH)]2(μ2-py) (3) were synthesized from copper(II) nitrate and sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzene-sulfonate (NaH2L), in the absence (for 1) and presence of imidazole (im) (for 2) or pyrazine (py) (for 3), and fully characterized. The complexes 1–3 have been tested as stereoselective C H activating catalysts for the model nitroaldol (Henry) condensation of nitroethane with various aldehydes in water. 1 was the most active catalyst affording 64−87% yields with syn/anti diasteroselectivities up to 77:23.

Heterometallic double Fe2O3–CoCl2, CoCl2–V2O5, MoO3–V2O5, and triple CuO–Fe2O3–CoCl2 3d metal dispersed systems were easily prepared by ball milling at room temperature and characterized by scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM), energydispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). They catalyze the microwave-assisted solvent-free heterogeneous oxidation of 1-phenylethanol to acetophenone with tert-butyl hydroperoxide (t-BuOOH) as oxidant, used as a model reaction. In most of the heterometallic systems a significant improvement in the catalytic activity was observed in comparison to homometallic ones. For the tested catalytic systems and experimental conditions, the CuO–Fe2O3–CoCl2 and Fe2O3–CoCl2 systems exhibit the highest activity with maximum 78% yield and TON 39 after 1 h. The possibility of magnetic recovery of the catalysts was demonstrated for the Fe2O3–CoCl2 (3:1) system. info:eu-repo/semantics/publishedVersion

3d metal (Cu, Fe, Co, V) containing composite catalysts for the solvent-free microwave-assisted transformation of 1-phenylethanol to acetophenone with tert-butyl hydroperoxide (TBHP) as oxidant were prepared by ball milling. The influence of multiwalled carbon nanotubes (CNTs) and graphene oxide (GO) additives on the catalytic activity of the catalysts was studied. CNTs or GO were mixed by ball milling with the metal salts (CoCl2), oxides (CuO, Fe2O3, V2O5) or binary systems (Fe2O3-CoCl2, CoCl2-V2O5, CuO-Fe2O3). For CoCl2-based catalytic systems, addition of small amounts (0.1–5%) of CNTs or GO leads to significant improvement in catalytic activity, e.g. 1% of the CNTs additive allows to rise yields from 28 to 77%, under the same catalytic conditions. The CoCl2-5%CNTs composite is the most active among the studied ones with 85% yield and TON of 43 after 1 h.

In this review we attempted to answer the question: how to construct complex functionalized molecules with significant added value from cheap and readily available alcohols in the simplest and most efficient manner? Accordingly, recent developments (mainly from the last 5 years) in the field of one-pot multiple transformations of alcohols are overviewed in terms of the process simplification and optimization, sustainability, atom-, bond-, step- and redox- economy. A particular attention has been paid to chemo- and stereoselective transformations with specific formation of particular bonds and configurations, leaving other parts of substrates unchanged.

Chemical transformations induced by mechanical force in solids are remarkable since they facilitate syntheses that are normally difficult to achieve in solution and thus allow the preparation of new molecules and materials or drastic improvements of the yields and selectivities. In many cases, the noncovalent interactions (NCIs) with mechanochemical treatment differ significantly from those which occur in analogous solvent-assisted processes. Moreover, if a “mechanocatalyst” is introduced into the system, it can additionally alter the NCIs, bond energies and properties of the reaction intermediates. As result, the outcome of many mechanocatalytic reactions can be very different in terms of efficiency or even reaction pathways compared with the traditional solution-based procedures or noncatalytic mechanochemical processes. Accordingly, in this chapter, certain mechanocatalytic reactions in which the NCIs play a key role are overviewed and discussed. Additionally, an overview of some experimental techniques used to study mechanochemical activation and the respective NCIs is also provided.

Intensification of chemical processes according to the motto “faster, simpler, greener” is among the main concerns nowadays. One of the ways of intensification is the application of synergistic catalytic effects when the overall efficiency of a composite catalyst is much higher than the sum of the component activities. Here, we report on the preparation of synergistic catalytic materials by a simple and straightforward ball milling procedure. Oxidation of benzoin was selected as a model reaction to demonstrate the viability of the concept. For the V2O5–TiO2 (95 : 5) composite material, the synergistic effect is triggered by low power microwave irradiation with more than a tenfold jump in the catalytic activity in comparison to the activities of the individual components.

Este trabalho foi financiado pelo Concurso Anual para Projetos de Investigação, Desenvolvimento, Inovação e Criação Artística (IDI&CA) 2016 do Instituto Politécnico de Lisboa. Código de referência IPL/2016/MechSynCat_ISEL The effect of microwave and mechanochemical ball milling energy inputs was studied for the peroxidative oxidation (with aqueous H2O2) of cyclohexane to cyclohexanol and cyclohexanone, over CoCl2 and/or V2O5 dispersed (μm scale) catalysts. A maximum total yield of cyclohexanol and cyclohexanone of 43% after 1 h of reaction at 30 °C, in acetonitrile and under microwave irradiation (5 W), was achieved over the CoCl2–V2O5 (3 : 1) catalyst prepared by ball milling. Cyclohexanol is the main final product with a selectivity of up to 93% over cyclohexanone. Conducting the oxidation reaction under microwave irradiation under the same conditions but without any mechanochemical treatment of the catalyst prior to use resulted in a lower total yield of 30% with a lower selectivity (69%) towards cyclohexanol over cyclohexanone. The sole application of mechanochemical treatment for the catalyst preparation and the catalytic oxidation of cyclohexane allowed to reach yields of 29% after 1 h of reaction, at room temperature, without microwave irradiation and any additive and in the absence of any organic solvent. Ball milling is shown to provide a convenient, solvent-free method to disperse these solid catalysts and to promote the above cyclohexane oxidation, although, in the latter case, not so effectively as microwave irradiation. info:eu-repo/semantics/publishedVersion

Two complexes with isoindole-core ligands of general formula [M{C6H4C(NH2)NC(ONCMe2)2}2](NO3)2 (M = Co for 1 and M = Ni for 2) were studied as catalysts for the mild stereoselective alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as a main model substrate. Complex 1 disclosed a pronounced activity, with high retention of stereoconfiguration of substrates (>98% for cis-1,2-DMCH) and highest cis/trans ratio of tertiary alcohols (products) of 56, under mild conditions. The best achieved yields of tertiary cis-alcohols were of 13.7 and 50.5%, based on the substrate (cis-1,2-DMCH) and the oxidant (m-CPBA) respectively. Kinetic experiments, high bond and stereoselectivity parameters, kinetic isotope effect of 7.2(2) in the oxidation of cyclohexane, and incorporation of 18O from H218O support the involvement of CoIVO high-valent metal–oxo intermediates as main C–H attacking species.

A new catalytic system for the anaerobic oxidation of benzyl alcohols using a tetrazole-amino-saccharin organocatalyst has been established. In a solvent-free and microwave assisted process comprising aqueous tert-butyl hydroperoxide (TBHP) as oxidant, a variety of benzyl alcohols has been efficiently converted to aldehydes under mild conditions. Most reactions are complete within 30 min and the catalyst exhibits varied functional group compatibility. A catalytic cycle for the oxidation of the alcohols promoted by the tetrazole-amino-saccharin derivative is outlined involving radical species. DFT calculations performed for the oxidation of benzyl alcohol with and without organocatalyst show that the rate limiting step of the whole reaction is the cleavage of the O-O bond in TBHP with the subsequent hydrogen abstraction from the alcohol. The tetrazole-amino-saccharin organocatalyst assists the H-abstraction from benzyl alcohol by the bound HO center dot radical. The simplicity, selectivity and softness of reaction conditions of the studied organocatalytic protocol suggest a great potential for extensive use in synthetic chemistry. (C) 2017 Elsevier B.V. All rights reserved. Foundation for Science and Technology (FCT), Portugal [IF/01270/2013/CP1163/CT0007] FCT [SFRH/BPD/99851/2014, SFRH/BD/52370/2013, PD/00248/2012]

The reaction of copper(II) nitrate hydrate with sodium 2-[2-(2,4-dioxopentan-3-ylidene)hydrazinyl]terephthalate (Na2HL1) in the absence or presence of imidazole (im) leads to the new complexes [(H2O)Cu0.5{(μ-L1-1κO:2κ3N,O′,O″)Cu(H2O)2}]2 (1) and [Cu(im)(μ-HL1-1κO:2κ3N,O,O′)]2 (2), respectively, whereas the 1D coordination polymer [Cu2(H2O)2(μ-H2L2-1κ3N,O,O′:2κO″)(μ-L2-1κ3N,O,O′:2κ2N′,O″)]n (3) is obtained from Cu(NO3)2·2.5H2O and sodium 2-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]terephthalate (Na2HL2). All of the compounds were characterized by ESI-MS, IR spectroscopy, elemental analysis and X-ray diffraction analysis. Di- or tri-deprotonated ligands display different coordination modes and lead to distinct nuclearities of the CuII complexes depending on the conditions used for the syntheses. Complexes 1–3 were successfully tested as dual-role catalysts for cyclohexane oxidation under acid-free conditions in the ionic liquid [1-butyl-3-methylimidazolium tetrafluoroborate, (bmim)(BF4)] as well as in acetonitrile. The application of the ionic liquid (IL) increased the product yield and turnover number and decreased the reaction time, in comparison with those for the use of the conventional acetonitrile solvent. Easy recycling of the catalyst, with preservation of almost the initial activity and selectivity, was also achieved by using the IL medium.

In spite of its impressive record in medicinal chemistry, the role of barbituric acid H 3 BA (pyrimidine-2,4,6(1 H ,3 H ,5 H )-trione) in coordination, organometallic and supramolecular chemistries has not yet been analyzed and reviewed. However, H 3 BA can be readily functionalized and provides rich opportunities to create coordination bonds and non-covalent interactions. Thus, derivatives of H 3 BA (barbituric acids, BAs) are widely used for the preparation of a wide range of complexes with various metals of almost all groups of the periodic table. The review systematizes information on the synthesis, tautomerism, acid–base properties of BAs and their use for the construction of organometallic and coordination compounds, as well as coordination polymers and supramolecular assemblies. The role of different metal ions and the structure of BAs in directing the preparative pathways and tuning particular structural properties of the resulting compounds are discussed. Some valuable applications of BAs, in particular in the construction of molecular receptors, magnetic and nonlinear optic materials, bioactive compounds, drug cocrystal design, catalysis and photochemistry are also envisaged.

The water-soluble copper(II) complex [Cu(H2R)(HL)]∙H2O (1) was prepared by reaction of copper(II) nitrate hydrate with (E)-2-(((1-hydroxynaphthalen-2-yl)methylene)amino) benzenesulfonic acid (H2L) and diethanolamine (H3R). It was characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. 1 shows a high catalytic activity for the solvent-free microwave (MW) assisted oxidation of 1-phenylethanol with tert-butylhydroperoxide, leading, in the presence of TEMPO, to yields up to 85% (TON = 850) in a remarkably short reaction time (15 min, with the corresponding TOF value of 3.40 × 103 h− 1) under low power (25 W) MW irradiation.

New organically templated complexes {(C4H12N2)[MII(H2O)4(SeO4)2]}·2H2O [MII = Co (1), Cu (2) and Zn (3)] were prepared by slow evaporation of aqueous solution containing metal(II) carbonate, selenic acid and piperazine taken in 1:2:1 M ratio. The compounds 1–3 were characterized by IR spectroscopy, ESI-MS, elemental and single-crystal X-ray diffraction analyses. The structures of the compounds contain [C4H12N2]2+ cation, H2O molecules and the [MII(H2O)4(SeO4)2]2− anions interlinked by Ow–Hw⋯O and N–H⋯O hydrogen bonding. 1–3 and known analogous mixed salts (C6H14N2)[MII(H2O)6](SeO4)2 [MII = Ni (4), Zn (5)] (C6H12N2 = 1,4-diazabicyclo[2.2.2]octane) are effective catalysts in the synthesis of β-nitroalkanols from nitroethane and aliphatic or aromatic aldehydes with yields up to 93% and threo/erythro ratio up to 79:21.

Metal-free regioselective activation of a carbon–carbon bond in 1,3,5-triazine derivatives of β-diketones is easily achieved, in the absence of a catalyst, with the assistance of intramolecular hydrogen bonding.

Template condensation of CCl 3 CN and ammonia on zinc(II) (used as acetate) afforded, in one step, bis(2,4-bis(trichloromethyl)-1,3,5-triazapentadienato)-zinc(II) 1 , which was characterized by elemental analysis, ESI-MS, IR and X-ray single-crystal analysis. The complex 1 was shown to be an effective catalyst in the nitroaldol (Henry) reaction, providing high yields (up to 99%) and good diastereoselectivities ( threo/erythro up to 3:1) at ambient conditions.

The methods of synthesis of arylhydrazones of methylene active compounds (AHMACs) as well as the preparation and properties of their metal complexes are reviewed. Nuclearity, supramolecular arrangements and other features (e.g., solubility, redox potentials, catalytic and antibacterial activities) of the complexes can be controlled by the introduction of different substituents to the methylene active and/or the aromatic fragments of AHMAC and by variation of metal-ions used in the synthesis.

Mononuclear Cu(II) and Co(II) complexes comprising 2-methyltetrazole-saccharinate bidentate N,N-chelating ligand have been synthesized for the first time and tested as homogeneous catalysts for oxidation of secondary alcohols in a solvent-free and microwave assisted protocol using aqueous tertbutyl hydroperoxide (TBHP) as oxidant. The developed catalytic system exhibits broad functional group compatibility, allowing efficient and selective conversion of a variety of secondary alcohols, including allylic ones, into the corresponding ketones. With typical 0.2 mol% content of the catalyst and under 20-50 W microwave irradiation, most reactions are complete within 10 min, presenting TONs up to 5.5 x 10(2) and TOFs up to 1.1 x 10(4)h(-1). No additives and co-oxidants have been used, while TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) acts as inhibitor in most cases. A plausible reaction mechanism involving the new catalytic systems is outlined. (C) 2016 Elsevier B.V. All rights reserved.

New Cu II complexes [Cu(H 2 O)(μ-L 1 )Na(H 2 O)] n ·2 n H 2 O ( 4 ), [Cu(H 2 O)(μ-HL 2 )Na(H 2 O)] n ·2 n H 2 O ( 5 ) and [Cu(H 2 O)(μ-L 3 )Na(H 2 O)] n ·2 n H 2 O ( 6 ), bearing the SO 3 − or COO − -functionalized arylhydrazones of β-diketones (AHBDs) 3-(2-hydroxy-3-sulfo-5-nitrophenylhydrazone)pentane-2,4-dione (H 3 L 1 , 1 ), 3-(2-hydroxy-3,5-disulfophenylhydrazone)pentane-2,4-dione (H 4 L 2 , 2 ) or 1-ethoxy-2-(2-hydroxy-4-carboxyphenylhydrazone)butane-1,3-dione (H 3 L 3 , 3 ), were synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS and X-ray analysis (for 4 ). 4 – 6 were immobilized on the layered double hydroxides (LDH) [Zn 0.74 Al 0.26 (OH) 2 ]ǀ(NO 3 ) 0.26 ·0.23H 2 O and characterized by X-ray powder diffraction patterns (XRPD), UV–vis, IR spectroscopies, thermogravimetric (TG) and differential thermal (DTA) analyses. The heterogenized Cu II AHBD-LDH systems catalyze the peroxidative oxidation (with TBHP or H 2 O 2 as oxidant) of alkanes (cyclohexane, n -pentane, n -hexane, n -heptane, n -octane) mainly to alcohols, under mild conditions, and can be recycled at least five times without significant loss of activity, with overall yields of 10–15% per cycle depending on the catalyst used. Regioselectivity at position 2 of the alkane is favoured by the heterogenized catalysts.

The reaction of CuII acetate with the new sulfo-functionalized arylhydrazone of β-diketone 2-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]benzenesulfonic acid (H2L, 1) in aqueous methanol solution led to the formation of the 2D coordination polymer {[Cu4(1κ2O,κN:2κO,κN-L)4(μ-OH2)2]·H2O}n (2). However, when the reaction was peformed in the presence of the N-containing species cyanoguanidine (cyg), 3,5-dimethyl-1H-pyrazole (dp), 2,2′-bipyridine (bpy) or pyrazine (py), the mononuclear (H3O+)2[Cu(κ2O,κN-L)2] (4), [Cu(κ2O,κN-L)(dp)2] (3) or [Cu(κ2O,κN-L)(κ2N-bpy)] (5) or dinuclear [{Cu(κ2O,κN-L)(H2O)}2(κ-py)]·CH3OH (6) complexes were obtained, respectively. The compounds were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis and, for 1, by 1H and 13C NMR spectroscopy. The CuII complexes 2–6 act as catalyst precursors for the selective peroxidative (with TBHP) allylic oxidation of cyclohexene to cyclohex-2-enol (Cy-ol) and cyclohex-2-enone (Cy-one), formed in a Cy-one/Cy-ol ratio of up to 9 with total yields of around 70 % and TONs of up to 350.

A new water-soluble β-diketone azo derivative ― 3-(5-chloro-2-hydroxy-3-sulfophenylhydrazo)pentane-2,4-dione(H3L, 1) ― was synthesized and found to be stable in DMSO solution and in the solid state in the hydrazo tautomeric form. Its water-soluble complexes [Co(HL)(en)(H2O)]·4H2O (3) and the zwitterionic [Cu(L)(Hen)(H2O)] (4), with buffering properties, were prepared by reaction of cobalt(II) and copper(II) nitrates with the ethylenediammonium (H2en) salt of 1, (H2en)(HL) (2). In the formation of 3 and 4, 1 is a chelating ligand, and a crucial synthetic and structural role is played by en, allowing the organization of water-soluble assemblies and influencing the overall 3D supramolecular arrangement. Compound 3 is the first cobalt complex with an azo derivative of a β-diketone. Complex 4 acts as catalyst precursor for the aerobic TEMPO-mediated selective oxidation of benzylic alcohols to the corresponding aldehydes in aqueous media.

The new three-dimensional (3D) heterometallic Cu(II)/Fe(II) coordination polymers [Cu(6)(H(2)tea)(6)Fe(CN)(6)](n)(NO(3))(2n)·6nH(2)O (1) and [Cu(6)(Hmdea)(6)Fe(CN)(6)](n)(NO(3))(2n)·7nH(2)O (2) have been easily generated by aqueous-medium self-assembly reactions of copper(II) nitrate with triethanolamine or N-methyldiethanolamine (H(3)tea or H(2)mdea, respectively), in the presence of potassium ferricyanide and sodium hydroxide. They have been isolated as air-stable crystalline solids and fully characterized including by single-crystal X-ray diffraction analyses. The latter reveal the formation of 3D metal-organic frameworks that are constructed from the [Cu(2)(μ-H(2)tea)(2)](2+) or [Cu(2)(μ-Hmdea)(2)](2+) nodes and the octahedral [Fe(CN)(6)](4-) linkers, featuring regular (1) or distorted (2) octahedral net skeletons. Upon dehydration, both compounds show reversible escape and binding processes toward water or methanol molecules. Magnetic susceptibility measurements of 1 and 2 reveal strong antiferromagnetic [J = -199(1) cm(-1)] or strong ferromagnetic [J = +153(1) cm(-1)] couplings between the copper(II) ions through the μ-O-alkoxo atoms in 1 or 2, respectively. The differences in magnetic behavior are explained in terms of the dependence of the magnetic coupling constant on the Cu-O-Cu bridging angle. Compounds 1 and 2 also act as efficient catalyst precursors for the mild oxidation of cyclohexane by aqueous hydrogen peroxide to cyclohexanol and cyclohexanone (homogeneous catalytic system), leading to maximum total yields (based on cyclohexane) and turnover numbers (TONs) up to about 22% and 470, respectively.

3-(2-Hydroxy-4-nitrophenylhydrazo)pentane-2,4-dione (H2L, 1) was synthesized by azocoupling of diazonium salts of 2-hydroxy-4-nitroaniline with pentane-2,4-dione and shown to exist in the hydrazone tautomeric form in the free state and in its new dicopper(II) complex [Cu2(H2O)2(μ-L)2] (2) whose X-ray crystal structure was determined. Complex 2 acts as a catalyst, under mild conditions, for the peroxidative oxidation (with H2O2) of cyclohexane to cyclohexanol, cyclohexanone and cyclohexyl hydroperoxide, in MeCN/H2O, and for the aerobic TEMPO-mediated selective oxidation of benzylic alcohols to the corresponding aldehydes, thus showing that azoderivatives of β-diketones can be the suitable ligands for such types of reactions.

The previously unknown reactions between phthalonitriles, 1,2-(CN)2(C6)R1R2R3R41 (1 a, R1=R2=R3=R4=H; 1 b, R1=R2=R4=H, R3=CH3; 1 c, R1=R4=H, R2=R3=Cl; 1 d, R1=R2=R3=R4=Cl; 1 e, R1=R2=R3=R4=F), and a cyclic nitrone, −O+NCHCH2CH2CMe22, proceed under heating in a sealed tube to give phthalimides 3, 2-oxadiazolyl-benzonitriles 4 or ortho-bis(oxadiazolyl)tetrafluorobenzene 4 e′. In the presence of palladium(II) chloride, phthalonitriles 1 react with 2 at room temperature, to give bis(pyrrolidin-2-ylidene)phthalamide PdII complexes 5 via metal-promoted rupture of the NO bond of the oxadiazoline ring. The ketoimine ligands thus generated can be liberated from the metal by displacement with a diphosphine. Although the first [2+3] cycloaddition of 2 to 1 can occur in the absence of the metal to give the mono-cycloadducts 4, the second [2+3] coupling at the still-unreacted cyano group requires its activation by coordination to PdII, affording complexes 6 containing two ligated oxadiazolyl-benzonitriles. These ligands undergo either i) further cycloaddition with 2 to afford ultimately (upon rearrangement) the bis(pyrrolidinylidene)phthalamide complexes 5 or ii) NO bond cleavage in the oxadiazoline ring with intramolecular attack of the imine nitrogen on the cyano carbon and bridging to a second PdII center to afford dimeric palladium(II) complexes 7, with chloride bridges, that bear a dihydropyrrolyl-iminoisoindolinone, a new type of ligand. The compounds were characterized by IR, 1H, and 13C NMR spectroscopy, ESI MS or FAB+ MS, elemental analyses and, in the case of 4 c, 5 a, 5 c, and 7 c, also by X-ray diffraction analysis. Complexes 5 a and 7 c show high catalytic activity for the Suzuki–Miyaura cross-coupling reaction of bromobenzene and phenylboronic acid and give biphenyl in high yields with turnover frequencies (TOFs) of up to 9.0×105 h−1.

The mono-, di-, tri-, tetra- and polynuclear copper(II) triethanolamine (H 3 tea) complexes [Cu(H 2 tea)(N 3 )] (1), [Cu 2 (H 2 tea) 2 (XC 6 H 4 COO) 2 ]. 2 H 2 O (X=4-H 2a, 4-CH 3 2b, 3-Cl 2c), [Cu 3 (H 2 tea) 2 -(4-OC6H4COO) 2 (H 2 O)].4H 2 O (3), [O C Cu 4 (tea) 4 -(BOH) 4 ][BF 4 ] 2 (4) and [Cu 2 (H 2 tea) 2 {μ-C 6 H 4 (COO) 2 -1,4} n ].2n H 2 O (5), respectively, are highly active and selective catalysts or catalyst precursors for the peroxidative oxidation of cyclohexane, in acetonitrile, to a cyclohexanol and cyclohexanone mixture, by aqueous hydrogen peroxide in acidic medium (liquid biphasic catalysis) at room temperature and atmospheric pressure. The effects on the catalytic activity of various factors, e.g., the relative amounts of cyclohexane, oxidant, catalyst, solvent and nitric acid, reaction time, catalyst recycling and impact of both carbon- and oxygen-centred radical traps (supporting mainly radical mechanisms) were investigated and allowed us to achieve yields and TONs up to ca. 39% and 380, respectively, corresponding to the most active copper systems so far reported for the oxidation of cyclohexane under mild conditions. The catalysts can be reused for recycling and, at least complex 4 maintains almost the same level of activity even after five reaction cycles. The preparation of the new complexes 1, 2b and 2c by self-assembly at room temperature, and their full characterization by IR spectroscopy, FAB-MS + , elemental and X-ray diffraction structural (for 1 and 2c) analyses are also reported.

The equilibrium compositions of the products of hydrolysis of Fe(III) and Cr(III) in their single or binary nitrate solutions, as a function of pH and neutralisation degree have been established and Fe(III)–Cr(III) hydroxides and products of their thermolysis have been obtained and characterized by potentiometric titration, thermal analysis, IR spectroscopy and X-ray powder diffraction, and an Fe(III)–Cr(III) interaction recognised in the binary systems. The obtained aquahydroxo complexes and metal hydroxides have been applied as catalysts for the homogeneous or heterogeneous, respectively, peroxidative oxidation of cyclohexane and cyclopentane to the corresponding ketones and alcohols, at room temperature. The effects of various parameters, such as pH, degree of neutralisation and reagents molar ratios, have been investigated and correlations between the catalytic activity and the form of the hydroxo complex were recognised for the homogeneous systems, whereas for the heterogeneous mixed (heteronuclear) hydroxides a synergic effect has been detected for the oxidation of cyclohexane, the catalytic activity (which can reach 30% yields and 30 turnover numbers (TONs)) being above those of the individual hydroxides.

Two complexes [KLa(HL(1))2{(CH3)2NCHO}2(H2O)3] (1) and [Sm(H2O)9](E-H2L(2))3·2H2O (2) were synthesized by the reaction of lanthanum(III) and samarium(III) nitrates with potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate (KH2L(1)) and potassium (E,Z)-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate (KH2L(2)), respectively. Both complexes were fully characterized by elemental analysis, IR, (1)H and (13)C NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. Cooperative E,Z→E isomerization of KH2L(2), induced by resonance assisted hydrogen bonding and ionic interactions, occurs upon the interaction with Sm(III). Catalytic activities of KH2L(1,2) and their lanthanide derivatives were evaluated in the Henry reaction of nitroethane with a variety of aromatic and aliphatic aldehydes. Good yields (up to 91%) and diastereoselectivities (syn/anti 3 : 1) were observed in the reactions catalyzed by 1 in water.

In spite of its impressive record in medicinal chemistry, the role of barbituric acid H 3 BA (pyrimidine-2,4,6(1 H ,3 H ,5 H )-trione) in coordination, organometallic and supramolecular chemistries has not yet been analyzed and reviewed. However, H 3 BA can be readily functionalized and provides rich opportunities to create coordination bonds and non-covalent interactions. Thus, derivatives of H 3 BA (barbituric acids, BAs) are widely used for the preparation of a wide range of complexes with various metals of almost all groups of the periodic table. The review systematizes information on the synthesis, tautomerism, acid–base properties of BAs and their use for the construction of organometallic and coordination compounds, as well as coordination polymers and supramolecular assemblies. The role of different metal ions and the structure of BAs in directing the preparative pathways and tuning particular structural properties of the resulting compounds are discussed. Some valuable applications of BAs, in particular in the construction of molecular receptors, magnetic and nonlinear optic materials, bioactive compounds, drug cocrystal design, catalysis and photochemistry are also envisaged.

One-pot template condensation of CCl3CN 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{NHC(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) 3.155 (2) > 3.133 (1) A]. Compounds 1–3 and the related di(triazapentadienato)-Cu(II) complex [Cu{NHC(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.

Template condensation of CCl 3 CN and ammonia on zinc(II) (used as acetate) afforded, in one step, bis(2,4-bis(trichloromethyl)-1,3,5-triazapentadienato)-zinc(II) 1 , which was characterized by elemental analysis, ESI-MS, IR and X-ray single-crystal analysis. The complex 1 was shown to be an effective catalyst in the nitroaldol (Henry) reaction, providing high yields (up to 99%) and good diastereoselectivities ( threo/erythro up to 3:1) at ambient conditions.

Three complexes are synthesized and tested for their activity in the diastereoselective Henry-reaction, with the shown catalyst being the most effective one.

Bis(1-phenylethanaminium) disulfatotetraaquazincate(II) dihydrate (C 8 H 12 N) 2 [Zn(H 2 O) 4 (SO 4 ) 2 ]·2H 2 O ( 1 ), bis(1H-benzo[d]imidazolium) hexaaquazinc(II) bis(sulfate) tetrahydrate (C 7 H 7 N 2 ) 2 [Zn(H 2 O) 6 ](SO 4 ) 2 ·4H 2 O ( 2 ) and bis(2-methyl-1H-imidazolium) hexaaquazinc(II) bis(sulfate) dihydrate (C 4 H 7 N 2 ) 2 [Zn(H 2 O) 6 ](SO 4 ) 2 ·2H 2 O ( 3 ) have been synthesized and fully structurally characterized including single-crystal X-ray diffraction analysis. 1 – 3 are organically templated hybrid layered materials comprising aquazinc(II) and aminium cations and sulfate anions. 1 – 3 are effective catalysts in the asymmetric Henry reaction; 1 being the most efficient one (yields up to 85% and threo/erythro diastereoselectivity up to 89:11).

A one-pot template condensation of 2-(2-(dicyanomethylene)hydrazinyl)benzenesulfonic acid (H(2)L(1), 1) or 2-(2-(dicyanomethylene)hydrazinyl)benzoic acid (H(2)L(2), 2) with methanol (a), ethylenediamine (b), ethanol (c) or water (d) on copper(II), led to a variety of metal complexes, that is, mononuclear [Cu(H(2)O)(2)(κO(1),κN(2)L(1a)] (3) and [Cu(H(2)O)(κO(1),κN(3)L(1b))] (4), tetranuclear [Cu(4)(1κO(1),κN(2):2κO(1)L(2a))(3)-(1κO(1), κN(2):2κO(2)L(2a))] (5), [Cu(2)(H(2)O)(1κO(1), κN(2):2κO(1)L(2c))-(1κO(1),1κN(2):2κO(1),2 κN(1)- L(2c))](2) (6) and [Cu(2)(H(2)O)(2)(κO(1),κN(2)- L(1dd))-(1κO(1),κN(2):2κO(1)L(1dd))(μ-H(2)O)](2·) 2H(2)O (7·2H(2)O), as well as polymer- ic [Cu(H(2)O)(κO(1),1κN(2):2κN(1)L(1c))](n) (8) and [Cu(NH(2)C(2)H(5))(κO(1),1κN(2):2κN(1)L(2a))](n) (9). The ligands 2-SO(3)H-C(6)H(4)-(NH)N=C{(CN)[C(NH(2))-(=NCH(2)CH(2)NH(2))]} (H(2)L(1b), 10), 2-CO(2)H-C(6)H(4)-(NH)N={C(CN)[C(OCH(3))-(=NH)]} (H(2)L(2a), 11) and 2-SO(3)H-C(6)H(4)-(NH)N=C{C(=O)-(NH(2))}(2) (H(2)L(1dd), 12) were easily liberated upon respective treatment of 4, 5 and 7 with HCl, whereas the formation of cyclic zwitterionic amidine 2-(SO(3)(−))-C(6)H(4)-N=NC(-C=(NH(+))CH(2)CH(2)NH)(=CNHCH(2)CH(2)NH) (13) was observed when 1 was treated with ethylenediamine. The hydrogen bond-induced E/Z isomerization of the (HL(1d))(−) ligand occurs upon conversion of [{Na(H(2)O)(2)(μ-H(2)O)(2)}(HL(1d))](n) (14) to [Cu(H(2)O)(6)][HL(1d)](2)·2H(2)O (15) and [{CuNa(H(2)O)-(κN(1),1κO(2):2κO(1)L(1d))(2)}K(0.5)(μ-O)(2)]n·H(2)O (16). The synthesized complexes 3–9 are catalyst precursors for both the selective oxidation of primary and secondary alcohols (to the corresponding carbonyl compounds) and the following diastereoselective nitroaldol (Henry) reaction, with typical yields of 80–99%.

The aquasoluble Fe(III) complexes [Fe(H(2)O)(3)(L(1))]∙4H(2)O (3) and [Fe(H(2)O)(3)(L(2))]∙3H(2)O (4), bearing the basic forms of 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxy-benzenesulfonic acid (H(3)L(1), 1) and 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid (H(3)L(2), 2), were synthesized and fully characterized including by X-ray crystal structural analysis. In the channels of the water-soluble 3D networks of 3 and 4, the uncoordinated water molecules are held by oxygen atoms of the carbonyl and sulfonyl groups, and by the water ligands. The Fe(III) coordination environment resembles that in the active sites of some mononuclear non-heme iron-containing enzymes. The complexes show a high catalytic activity for the peroxidative oxidation (with aqueous H(2)O(2)) of C(5)-C(8) cycloalkanes to the corresponding alcohols and ketones under mild conditions. The effects of various factors, such as amounts of oxidant, catalyst and HNO(3) additive, were investigated allowing to reach overall yields of ca. 25% and turnover numbers (TONs) up to 290. The catalytic reactions proceed via both oxygen- and carbon-radicals as shown by radical trap experiments.

Template combination of copper acetate (Cu(AcO)(2)⋅H(2)O) with sodium dicyanamide (NaN(C≡N)(2), 2 equiv) or cyanoguanidine (N≡CNHC(=NH)NH(2), 2 equiv) and an alcohol ROH (used also as solvent) leads to the neutral copper(II)-(2,4-alkoxy-1,3,5-triazapentadienato) complexes [Cu{NH=C(OR)NC(OR)=NH}(2)] (R = Me (1), Et (2), nPr (3), iPr (4), CH(2)CH(2)OCH(3) (5)) or cationic copper(II)-(2-alkoxy-4-amino-1,3,5-triazapentadiene) complexes [Cu{NH=C(OR)NHC(NH(2))=NH}(2)](AcO)(2) (R = Me (6), Et (7), nPr (8), nBu (9), CH(2)CH(2)OCH(3) (10)), respectively. Several intermediates of this reaction were isolated and a pathway was proposed. The deprotonation of 6-10 with NaOH allows their transformation to the corresponding neutral triazapentadienates [Cu{NH=C(OR)NC(NH(2))=NH}(2)] 11-15. Reaction of 11, 12 or 15 with acetyl acetone (MeC(=O)CH(2)C(=O)Me) leads to liberation of the corresponding pyrimidines NC(Me)CHC(Me)NCNHC(=NH)OR, whereas the same treatment of the cationic complexes 6, 7 or 10 allows the corresponding metal-free triazapentadiene salts {NH(2)C(OR)=NC(NH(2))=NH(2)}(OAc) to be isolated. The alkoxy-1,3,5-triazapentadiene/ato copper(II) complexes have been applied as efficient catalysts for the TEMPO radical-mediated mild aerobic oxidation of alcohols to the corresponding aldehydes (molar yields of aldehydes of up to 100 % with >99 % selectivity) and for the solvent-free microwave-assisted synthesis of ketones from secondary alcohols with tert-butylhydroperoxide as oxidant (yields of up to 97 %, turnover numbers of up to 485 and turnover frequencies of up to 1170 h(-1)).

The possibility of tunable regioselective activation of a dinitrile towards nucleophilic attack was demonstrated. For that, a sulfo-arylhydrazone unit was introduced into malononitrile and the thus formed intramolecular hydrogen bond systems assisted specific nucleophilic attacks to the cyano moieties leading to a variety of amidines, carboxamides and iminoesters depending on the nucleophiles and conditions used.

Reactions of copper(II) with 3-phenylhydrazopentane-2,4-diones X-2-C(6)H(4)-NHN=C{C(=O)CH(3)}(2) bearing a substituent in the ortho-position [X = OH (H(2)L(1)) 1, AsO(3)H(2) (H(3)L(2)) 2, Cl (HL(3)) 3, SO(3)H (H(2)L(4)) 4, COOCH(3) (HL(5)) 5, COOH (H(2)L(6)) 6, NO(2) (HL(7)) 7 or H (HL(8)) 8] lead to a variety of complexes including the monomeric [CuL(4)(H(2)O)(2)]·H(2)O 10, [CuL(4)(H(2)O)(2)] 11 and [Cu(HL(4))(2)(H(2)O)(4)] 12, the dimeric [Cu(2)(H(2)O)(2)(μ-HL(2))(2)] 9 and the polymeric [Cu(μ-L(6))](n)] 13 ones, often bearing two fused six-membered metallacycles. Complexes 10-12 can interconvert, depending on pH and temperature, whereas the Cu(II) reactions with 4 in the presence of cyanoguanidine or imidazole (im) afford the monomeric compound [Cu(H(2)O)(4){NCNC(NH(2))(2)}(2)](HL(4))(2)·6H(2)O 14 and the heteroligand polymer [Cu(μ-L(4))(im)](n)15, respectively. The compounds were characterized by single crystal X-ray diffraction (complexes), electrochemical and thermogravimetric studies, as well as elemental analysis, IR, (1)H and (13)C NMR spectroscopies (diones) and ESI-MS. The effects of the substituents in 1-8 on the HOMO-LUMO gap and the relative stability of the model compounds [Cu(OH)(L(8))(H(2)O)]·H(2)O, [Cu(L(1))(H(2)O)(2)]·H(2)O and [Cu(L(4))(H(2)O)(2)]·H(2)O are discussed on the basis of DFT calculations that show the stabilization follows the order: two fused 6-memberedtwo fused 6-membered/5-memberedone 6-membered metallacycles. Complexes 9, 10, 12 and 13 act as catalyst precursors for the peroxidative oxidation (with H(2)O(2)) of cyclohexane to cyclohexanol and cyclohexanone, in MeCN/H(2)O (total yields of ca. 20% with TONs up to 566), under mild conditions.

A facile, efficient and selective solvent-free synthesis of ketones from secondary alcohols with tert-butylhydroperoxide (TBHP) as the oxidant under microwave irradiation is achieved, where the copper(II) 2,4-alkoxy-1,3,5-triazapentadienato complexes are efficient catalysts providing high yields (up to 100%), TONs (up to 890) and TOFs (up to 1780 h−1).

A facile, efficient and selective solvent-free synthesis of ketones from secondary alcohols with tert-butylhydroperoxide (TBHP) as the oxidant under microwave irradiation is achieved, where the copper(ii) 2,4-alkoxy-1,3,5-triazapentadienato complexes are efficient catalysts providing high yields (up to 100%), TONs (up to 890) and TOFs (up to 1780 h(-1)).

[2 + 3] Cycloaddition reactions of the organonitriles RCN 1 (R = Me (1a), Et (1b), p-IC(6)H(4) (1c), p-BrC(6)H(4) (1d), p-ClC(6)H(4) (), p-FC(6)H(4) (1e)) with the pyrroline N-oxide (-)O(+)[upper bond 1 start]N[double bond, length as m-dash]CHCH(2)CH(2)C[upper bond 1 end]Me(2) in the presence of PdCl(2) proceed at room temperature for 12 h and allow the isolation of the corresponding palladium(ii) complexes trans-[PdCl(2){[upper bond 1 start]N[double bond, length as m-dash]C(R)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2)}(2)] 3a-3f containing fused bicyclic Delta(4)-1,2,4-oxadiazoline ligands, in good to excellent yields (75-90%). Treatment of trans-[PdCl(2)(EtCN)(2)] with the nitrone in acetone or propionitrile at room temperature affords, in good yield, (R = Et), confirming that complexes 3 are formed via nitrile activation by coordination. These reactions proceed with high diastereoselectivity and afford mixtures of enantiomers, due to the rigid conformation (E) of the cyclic nitrone 2. The oxadiazolines [upper bond 1 start]N[double bond, length as m-dash]C(R)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2) (R = Et (4b), p-FC(6)H(4) (4f)) are liberated upon reaction of complexes 3b,3f with a diphosphine (dppe). During the liberation of , the complex trans-[PdCl(2){[upper bond 1 start]N[double bond, length as m-dash]C(NHCOC(6)H(4)F-4)CH(2)CH(2)C[upper bond 1 end]Me(2)}(2)] was formed in a minor amount upon N-O bond cleavage of the oxadiazoline ring to give a pyrrolylbenzamide species coordinated by the N-atom of the pyrrolyl moiety. The compounds were characterized by IR, (1)H and (13)C NMR spectroscopies, ESI-MS, elemental analyses and, in the cases of 3b, 3d and 5, also by X-ray diffraction analyses. Complexes 3b and 3f show a high catalytic activity towards the microwave-assisted Suzuki-Miyaura cross-coupling reaction in aqueous medium, achieving a TON value of 2.7 x 10(5) and a TOF value of 1.1 x 10(6) h(-1).