Alkoxo bridged heterobimetallic CoIIISnIV compounds with face shared coordination octahedra: Synthesis, crystal structure and cyanosilylation catalysis

The self-assembly reaction of the Schiff base N,N’-ethylenebis(2-hydroxyacetophenoneimine) (H2L), CoCl2··6H2O and [SnPh2Cl2] led to the alkoxo-bridged heteroorganometallic CoIIISnIV complex [{SnPhCl2}(1κO2:2κO2N2-μ-L)(μ-OMe){CoPh}]·CH3OH·H2O (1) or [{SnPhCl2}(1κO2:2κO2N2-μ-L)(μ-OEt){CoPh}] (2) in MeOH or EtOH, respectively. The structures of these complexes are authenticated by single crystal X-ray diffraction analyses. They are derived from an intermetallic (Sn to Co) phenyl shift, leading to face-shared distorted octahedral coordination geometries. The complexes were tested as homogeneous catalysts for the solvent-free cyanosilylation reaction of benzaldehyde with trimethylsilyl cyanide (TMSCN) under low power microwave irradiation at 50°C. They exhibited a high catalytic activity, yielding (for catalyst 1) up to 93% of the cyano-derivative from benzaldehyde in 90 minutes. © 2021 Elsevier B.V

Noncovalent interactions in alkane chemistry

The selective functionalization of alkanes remains one of the mainstream objectives of modern synthetic chemistry, because these inert hydrocarbons derived from natural gas and oil are the most readily available (and inexpensive) natural carbon resources. Moreover, noncovalent interactions (hydrogen, halogen, chalcogen, pnicogen, tetrel, and icosagen bonds, as well as agostic, anagostic, π-π stacking, n-π*, π-cation and π-anion interactions, etc.) or their cooperation with coordination bonds can be employed for selective activation of covalent bonds in synthetic operations. According to the CCDC structural database, many cyclic and acyclic alkanes have been isolated as solid organic or inorganic associates, combined via noncovalent interactions. These interactions can be used in separation, transportation, or storage of alkanes and can weaken C-H or C-C bonds eventually toward their functionalization, issues that are discussed in this chapter. © 2019 John Wiley & Sons Ltd

Polyaromatic Carboxylate Ligands Based Zn(II) Coordination Polymers for Ultrasound-Assisted One-Pot Tandem Deacetalization–Knoevenagel Reactions

Solvothermal reactions between the polyaromatic group containing carboxylic acid proligands 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H2L1) and 5-{(anthracen-9-ylmethyl)amino} isophthalic acid (H2L2) with Zn(NO3)2·6H2O led to the formation of the new 1D coordination polymer [Zn(L1)(NMF)]n (1) and four other coordination polymers, [Zn(L1)(DMF)]n (2), [Zn(L1)(4,4′-Bipy)]n (3), [Zn(L2)(DMF)(H2O)2 ]n·n(H2O) (4) and [Zn2(L2)2 (DMF)(CH3OH)]n (5), which were previously reported by our group. Single crystal X-ray diffraction analyses revealed that the CP 1 has a one-dimensional (1D) double-chain-type structure similar to that of CP 2. For CP 3, the assembly of the Zn(II) ion with a deprotonated L12− ligand and 4,4′-bipyridine produces a 3D network. CP 4 and 5 exhibit 1D linear and 2D layered-type structures. The ultrasound-assisted tandem reactions promoted by CPs have not yet been well studied. Thus, in the present work, we have investigated the catalytic activities of the newly synthesized CP 1, as well as of the other CPs 2–5, towards the tandem deacetalization–Knoevenagel condensation reactions of various acetals under ultrasonic irradiation. They proved to be highly efficient, with special emphasis on catalyst 1, which completely converted the substrate (benzaldehyde dimethyl acetal) into the desired product (2-benzylidenemalononitrile) after 2 h. The stability of the catalysts, namely regarding the action of ultrasonic radiation, was demonstrated by their reuse, where only a slight loss of activity was observed after four cycles. Heterogeneity was also demonstrated, and no leaching was detected over the various cycles. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

A mixed valence Co^IIco^III2 field-supported single molecule magnet: Solvent-dependent structural variation

One-pot reaction of the Schiff base N,N’-ethylene bis(salicylaldimine) (H2L), CoCl2.6H2O, and [Ph2SnCl2] in acetone produces the mixed valence CoIICoIII 2 compound [CoIICoIII 2(μ-L)2(Ph)2(μ-Cl)2]·(CH3)2CO·H2O (1). Our recent study already revealed that the same reaction mixtures in methanol or ethanol produced a heterometallic SnIVCoIII (2) or monometallic CoIII complex (3), respectively. Comparison of these organometallic systems shows that the 2,1-intermetallic Ph shift occurs in any of those solvents, but their relevant structural features (mononuclear, dinuclear-heterometallic, and trinuclear mixed valence) are solvent dependent. Geometrical structural rotation is also discussed among the related organometallic CoIICoIII 2 systems. The AC magnetic susceptibility measurements indicate that 1 is a single molecule magnet (SMM), exhibiting a field-induced slow magnetic relaxation with two modes. The relaxation time for the low-frequency channel is as slow as τ~0.6 s at T = 2.0 K and BDC = 1.0 T

Oxido-and dioxido-vanadium(V) complexes supported on carbon materials: Reusable catalysts for the oxidation of cyclohexane

Oxidovanadium(V) and dioxidovanadium(V) compounds, [VO(OEt)L] (1) and [Et3NH][VO2L] (2), were synthesized using an aroylhydrazone Schiff base (5-bromo-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H2L). They were characterized by elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), (1H and51V) nuclear magnetic resonance (NMR), electrospray ioniza-tion mass spectrometry (ESI-MS) and single crystal X-ray diffraction analyses. Both complexes were immobilized on functionalized carbon nanotubes and activated carbon. The catalytic performances of 1 and 2, homogenous and anchored on the supports, were evaluated for the first time towards the MW-assisted peroxidative oxidation (with tert-butylhydroperoxide, TBHP) of cyclohexane under heterogeneous conditions. The immobilization of 1 and 2 on functionalized carbon materials improved the efficiency of catalytic oxidation and allowed the catalyst recyclability with a well-preserved catalytic activity. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

CO2 + ionic liquid biphasic system for reaction/product separation in the synthesis of cyclic carbonates

The possibility of using supercritical CO2 (scCO2) technology as a second step for extracting propylene carbonate produced from the coupling reaction between propylene oxide and CO2, was investigated. The coupling reaction was performed under biphasic gas-liquid conditions, using a zinc(II) complex of arylhydrazones of β-diketones (Zn(II)-AHBD) as metal catalyst, combined with tetrabutylammonium bromide (TBABr). 1-Ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) and methyltrioctylammonium chloride ([ALIQUAT][Cl]) were explored as reaction solvents, in order to efficiently solubilize the catalyst and retain the catalyst inside the reactor during the product extraction step. Results obtained were compared with other common used solvents as methyl ethyl ketone (MEK), ethyl lactate (EL), and polyethylene glycol 400 (PEG 400). [ALIQUAT][Cl] was selected as the most promising solvent and scCO2 extraction was effectively applied as a second step to isolate propylene carbonate from the catalyst system. Following this strategy, the catalyst system was reused three times, without loss of activity. © 201

New Microbe Killers: Self-Assembled Silver(I) coordination polymers driven by a cagelike aminophosphine

New Ag(I) coordination polymers, formulated as [Ag(μ-PTAH)(NO3)2]n (1) and [Ag(μ-PTA)(NO2)]n (2), were self-assembled as light- and air-stable microcrystalline solids and fully characterized by NMR and IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS(±), elemental analysis, powder (PXRD) and single-crystal X-ray diffraction. Their crystal structures reveal resembling 1D metal-ligand chains that are driven by the 1,3,5-triaza-7-phospaadamantane (PTA) linkers and supported by terminal nitrate or nitrite ligands; these chains were classified within a 2C1 topological type. Additionally, the structure of 1 features a 1D!2D network extension through intermolecular hydrogen bonds, forming a two-dimensional hydrogen-bonded network with fes topology. Furthermore, both products 1 and 2 exhibit remarkable antimicrobial activity against different human pathogen bacteria (S. aureus, E. coli, and P. aeruginosa) and yeast (C. albicans), which is significantly superior to the activity of silver(I) nitrate as a reference topical antimicrobial. © 2019 by the authors

Heterogeneous gold nanoparticle-based catalysts for the synthesis of click-derived triazoles via the azide-alkyne cycloaddition reaction

A supported gold nanoparticle-catalyzed strategy has been utilized to promote a click chemistry reaction for the synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition (AAC) reaction. While the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) has demonstrated the catalysis of the AAC reaction, additional robust catalytic systems complementary to the copper catalyzed AAC remain in high demand. Herein, Au nanoparticles supported on Al2 O3, Fe2 O3, TiO2 and ZnO, along with gold reference catalysts (gold on carbon and gold on titania supplied by the World Gold Council) were used as catalysts for the AAC reaction. The supported Au nanoparticles with metal loadings of 0.7–1.6% (w/w relative to support) were able to selectively obtain 1,4-disubstituted-1,2,3-triazoles in moderate yields up to 79% after 15 min, under microwave irradiation at 150◦ C using a 0.5–1.0 mol% catalyst loading through a one-pot three-component (terminal alkyne, organohalide and sodium azide) procedure according to the “click” rules. Among the supported Au catalysts, Au/TiO2 gave the best results. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

CO2 + ionic liquid biphasic system for reaction/product separation in the synthesis of cyclic carbonates

The possibility of using supercritical CO2 (scCO2) technology as a second step for extracting propylene carbonate produced from the coupling reaction between propylene oxide and CO2, was investigated. The coupling reaction was performed under biphasic gas-liquid conditions, using a zinc(II) complex of arylhydrazones of β-diketones (Zn(II)-AHBD) as metal catalyst, combined with tetrabutylammonium bromide (TBABr). 1-Ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) and methyltrioctylammonium chloride ([ALIQUAT][Cl]) were explored as reaction solvents, in order to efficiently solubilize the catalyst and retain the catalyst inside the reactor during the product extraction step. Results obtained were compared with other common used solvents as methyl ethyl ketone (MEK), ethyl lactate (EL), and polyethylene glycol 400 (PEG 400). [ALIQUAT][Cl] was selected as the most promising solvent and scCO2 extraction was effectively applied as a second step to isolate propylene carbonate from the catalyst system. Following this strategy, the catalyst system was reused three times, without loss of activity. © 201