Cyclic carbonate synthesis from CO2and epoxides using zinc(II) complexes of arylhydrazones of β-diketones

Zinc(II) complexes of arylhydrazones of β-diketones (AHBD) were used for the first time as catalysts combined with tetrabutylammonium bromide (TBABr), in the coupling reaction between CO2 and epoxides. The influence of pressure and temperature on cyclic carbonate formation was investigated, as well as the catalytic activity toward different substrates (e.g. styrene oxide, propylene oxide and cyclohexene oxide). The molar ratio between metal complex and TBABr was determined for maximum catalytic activity

Chalcogen bonding in synthesis, catalysis and design of materials

Chalcogen bonding is a type of noncovalent interaction in which a covalently bonded chalcogen atom (O, S, Se or Te) acts as an electrophilic species towards a nucleophilic (negative) region(s) in another or in the same molecule. In general, this interaction is strengthened by the presence of an electron-withdrawing group on the electron-acceptor chalcogen atom and upon moving down in the periodic table of elements, from O to Te. Following a short discussion of the phenomenon of chalcogen bonding, this Perspective presents some demonstrative experimental observations in which this bonding is crucial for synthetic transformations, crystal engineering, catalysis and design of materials as synthons/tectons. © 2017 The Royal Society of Chemistry

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

Chalcogen and Hydrogen Bonds at the Periphery of Arylhydrazone Metal Complexes

Ligands comprising an intramolecular resonance-assisted hydrogen bond (RAHB) and an intramolecular resonance-assisted chalcogen bond (RAChB) have been used to form Cu(II), Ag(I), and Cd(II) metal complexes. Both interactions undergo major changes on ligand binding to the metal even though metal-ligand binding does not directly involve either interactions. In fact, the RAChB synthon can act as an intermolecular H-bond donor or acceptor, is involved in intramolecular coordination-coupled proton transfer, or exhibits an ionic pattern. © 2022 American Chemical Society. All rights reserved

Water-soluble Al(iii), Fe(iii) and Cu(ii) formazanates: synthesis, structure, and applications in alkane and alcohol oxidations

A series of water-soluble metal formazanates, [Al2(OH)2(H2O)8](HL)2 (1), [{Fe(H2O)4}(HL)(H2L)]·2H2O (2) and [Cu(en)2(H2O)2][CuL(H2O)2]2 (3), were synthesized by the reaction of sodium 2-(2-((E)-cyano((E)-(2-sulfonatophenyl)diazenyl)methylene)hydrazineyl) benzenesulfonate (Na2HL) with Al(NO3)3·9H2O, FeCl3·6H2O and Cu(NO3)2·3H2O (in the presence of ethylenediamine) in methanol, respectively. The formazan pro-ligand Na2HL and its complexes 1-3 were characterized by ESI-MS, 1H/13C NMR (for Na2HL), IR spectroscopy, elemental and X-ray diffraction analyses (for 1-3). According to the X-ray analysis, the formazanate behaves as an anion or displays a mono- or bidentate coordination mode, for the Al, Fe or Cu centre, respectively. All complexes were tested as catalysts for the peroxidative (with H2O2) oxidation of cyclohexane and cyclohexanol to the coresponding organic products at room temperature. The complexes 2 and 3 are active homogeneous catalysts for the microwave-assisted peroxidative oxidation with aqueous H2O2 of cyclohexane (to cyclohexanol and cyclohexanone) and cyclohexanol to cyclohexanone. © 2022 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Chalcogen bonding in synthesis, catalysis and design of materials

Chalcogen bonding is a type of noncovalent interaction in which a covalently bonded chalcogen atom (O, S, Se or Te) acts as an electrophilic species towards a nucleophilic (negative) region(s) in another or in the same molecule. In general, this interaction is strengthened by the presence of an electron-withdrawing group on the electron-acceptor chalcogen atom and upon moving down in the periodic table of elements, from O to Te. Following a short discussion of the phenomenon of chalcogen bonding, this Perspective presents some demonstrative experimental observations in which this bonding is crucial for synthetic transformations, crystal engineering, catalysis and design of materials as synthons/tectons. © 2017 The Royal Society of Chemistry

Copper(II) complexes with carboxylic- or sulfonic-functionalized arylhydrazones of acetoacetanilide and their application in cyanosilylation of aldehydes

The new copper(II) complexes [Cu(HL1)(H2O)(CH3OH)] (1, H3L1 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzoic acid) and [Cu(HL2)(H2O)(CH3OH)] (2, NaH2L2 = sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate) were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. The coordination environment of the central copper(II) has a square pyramidal geometry, three sites being occupied by (HL1,2)2−, which chelates in the O,N,O fashion, while the two other sites are filled with the water and methanol ligands. Multiple intra- and intermolecular non-covalent interactions between the (HL1,2)2−, water and methanol ligands lead to supramolecular network. Both compounds 1 and 2 act as homogenous catalysts for the cyanosilylation reaction of a variety of both aromatic and aliphatic aldehydes with trimethylsilyl cyanide affording the corresponding cyanohydrin trimethylsilyl ethers in high yields (up to 90%) and at room temperature. © 2017 Elsevier B.V

Noncovalent Interactions at Lanthanide Complexes

Lanthanide complexes have attracted a widespread attention due to their structural diversity, as well as multifunctional and tunable properties. The development of lanthanide based functional materials has often relied on the design of the secondary coordination sphere of the corresponding lanthanide complexes. For instance, usually simple lanthanide salts (solvento complexes) do not catalyze effectively organic reactions or provide low yield of the expected product, whereas the presence of a suitable organic ligand with a noncovalent bond donor or acceptor centre (secondary coordination sphere) modifies the symmetry around the metal centre in lanthanide complexes which then successfully can act as catalysts in both homogenous and heterogenous catalysis. In this minireview, we discuss several relevant examples, based on X-ray crystal structure analyses, in which the hydrogen, halogen, chalcogen, pnictogen, tetrel and rare-earth bonds, as well as cation-π, anion-π, lone pair-π, π–π and pancake interactions, are used as a synthon in the decoration of the secondary coordination sphere of lanthanide complexes. © 2021 Wiley-VCH Gmb

Halogen bonding in cadmium(ii) MOFs: Its influence on the structure and on the nitroaldol reaction in aqueous medium

A solvothermal reaction of Cd(ii) with the dicarboxyl-functionalized arylhydrazone pro-ligands, 5-(2-(2,4,6-trioxotetrahydro-pyrimidin-5(2H)-ylidene)hydrazineyl)isophthalic acid (H5L1) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)isophthalic acid (H3L2), or their halogen bond donor centre(s) decorated analogs 2,4,6-triiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazineyl)isophthalic acid (H5L3) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)-2,4,6-triiodoisophthalic acid (H3L4), leads to the formation of known [Cd(H3L1)(H2O)2]n (1) and new {[Cd(HL2)(H2O)2(DMF)]·H2O}n (2), [Cd(H3L3)]n (3) and {[Cd2(μ-H2O)2(μ-H2L4)2(H2L4)2]·2H2O}n (4) coordination compounds, respectively. The aggregation of mononuclear units via Cd-OC and Cd-OH2 coordination and CAr-I⋯I types of intramolecular halogen bonds lead to a dinuclear tecton 4. Both CAr-I⋯O and CAr-I⋯I types of intermolecular halogen bonds play a fundamental role in the supramolecular architectures of the obtained metal-organic frameworks 3 and 4. Theoretical (DFT) calculations confirmed the presence of the CAr-I⋯O and CAr-I⋯I halogen bonds in 3 and 4 and allowed their characterisation. The formation of intermolecular noncovalent interactions between the attached iodine substituents to the hydrazone ligands and polar solvent (water or methanol) molecules promoted, at least in part, the solubility of the corresponding complexes (3 and 4), which act as homogeneous catalyst precursors in the Henry reaction between aldehydes and nitroethane. The corresponding β-nitroalkanol products were obtained in good yields (66-79%) and with good diastereoselectivity (threo/erythro ca. 72 : 28) in water at room temperature. © The Royal Society of Chemistry

Copper(II) complexes with carboxylic- or sulfonic-functionalized arylhydrazones of acetoacetanilide and their application in cyanosilylation of aldehydes

The new copper(II) complexes [Cu(HL1)(H2O)(CH3OH)] (1, H3L1 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzoic acid) and [Cu(HL2)(H2O)(CH3OH)] (2, NaH2L2 = sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate) were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. The coordination environment of the central copper(II) has a square pyramidal geometry, three sites being occupied by (HL1,2)2−, which chelates in the O,N,O fashion, while the two other sites are filled with the water and methanol ligands. Multiple intra- and intermolecular non-covalent interactions between the (HL1,2)2−, water and methanol ligands lead to supramolecular network. Both compounds 1 and 2 act as homogenous catalysts for the cyanosilylation reaction of a variety of both aromatic and aliphatic aldehydes with trimethylsilyl cyanide affording the corresponding cyanohydrin trimethylsilyl ethers in high yields (up to 90%) and at room temperature. © 2017 Elsevier B.V