Том 66, № 9 (2017)
- Год: 2017
- Статей: 28
- URL: https://journals.rcsi.science/1066-5285/issue/view/14924
Reviews
Nickel and palladium N-heterocyclic carbene complexes. Synthesis and application in cross-coupling reactions
Аннотация
N-Heterocyclic carbenes (NHCs) are widely used as ligands in catalysis by transition metal complexes. The catalytic activity of transition metal NHC complexes is much higher than that of the transition metal complexes bearing the phosphine and nitrogen-containing ligands. They show excellent catalytic performance in different transformations of the organic compounds, especially in the carbon—carbon and carbon—element bond forming reactions. Palladium NHC complexes are very efficient catalysts for the cross-coupling reactions. On the other hand, nickel is less expensive and regarded as a promising alternative to palladium and, therefore, it attracts increasing attention from the researches. The present review is focused on the recent advances in the synthesis of N-heterocyclic carbene complexes of nickel and palladium and their application in catalysis of cross-coupling reactions of organic, organoelement and organometallic compounds with organic halides.
Full Articles
Specific features of the adsorption of chlorinated methanes and water on carbon nanotubes and alumina
Аннотация
The adsorption of CH2Cl2, CH3Cl, CCl4, and H2O vapors on the surface of multi-walled carbon nanotubes and alumina in the temperature range of 10—25 °C was studied. Dependences of the isosteric heat of adsorption on the surface coverage were plotted. The initial heat of adsorption of dichloromethane, chloroform, and CCl4 on Al2O3 was found to be equal to 71, 28, and 31 kJ mol–1, respectively. In most cases, adsorption on the oxide adsorbent was characterized by a higher heat of adsorption compared to that found on the carbon material, which is apparently related to chemical interaction of sorbed molecules with the OH groups of the alumina surface.
Quantum chemical study of binuclear adducts of cobalt azomethine complexes with pyrene-4,5,9,10-tetraimine
Аннотация
A computer simulation of 2 : 1 adducts of cobalt azomethine complexes with pyrene-4,5,9,10-tetraimine was carried out within the framework of the density functional theory (DFT B3LYP*/6-311++G(d,p)). It was shown that the variation of the substituents at the nitrogen atoms of cobalt bischelates, as well as the annulation of the five-membered ring to the azomethine fragment, considerably affects the relative energies of the isomers with different spin states. Compounds, which can manifest one- and two-step redox-isomeric rearrangements, accompanied by the migration of paramagnetic centers, were revealed.
Nature and strength of weak intermolecular interactions with metal atoms in crystals of square-planar nickel(ii) complexes
Аннотация
The results of geometric analysis of 588 crystal structures of square-planar nickel complexes containing short intermolecular Ni…X contacts (X is a non-metal atom) are reported. The frequency of occurrence of Ni…X interactions of a particular type was evaluated depending on the nature of the X atom and geometric characteristics. The promolecular functions RDG and sign(λ2)•ρ(r) were used to analyze the character of Ni…X interactions in attractive/repulsive terms. The relative strength of these interactions was determined as the function of the nature of the X atom and the direction of charge transfer.
Intramolecular C—F→Ln dative interactions in lanthanide complexes with fluorinated ligands
Аннотация
Complexes reported in the literature and potentially capable of intramolecular C—F→Ln interactions were analyzed. It was proposed to use the ToposPro software for structural and topological analysis to search for intramolecular C—F→Ln interactions. The shortest detected Ln···F contact amounted to 2.374 Å, while the longest weak non-valence contact was 4.060 Å. For all lanthanide complexes with Ln···F distances shorter than 3.447 Å, only strong intramolecular (valence) interactions between these atoms were observed. These interactions can affect the physicochemical properties of complexes and they are to be taken into account in determination of the coordination environment of lanthanide atoms.
Ferrocene-containing tri- and tetranuclear cyclic copper(i) and silver(i) pyrazolates
Аннотация
New tri- and tetranuclear macrocyclic silver(i) and copper(i) 3-ferrocenyl-5-(trifluoromethyl)pyrazolates were prepared: [{(3-((η5-C5H4)Fe(η5-C5H5))-5-(CF3)-Pz}M]3 (M = Cu (1), Ag (2)) and [{(3-(( η5-C5H4)Fe(η5-C5H5))-5-(CF3)-Pz}Cu]4 (3). The structures of compounds were established by X-ray diffraction analysis. In the crystalline state, a planar trinuclear silver-containing macrocycliс pyrazolate and a saddle-shaped tetranuclear copper-containing macrocycle are formed. The introduction of a bulky substituent, ferrocene, into the pyrazole ligand results in complete shielding of the acidic metal sites, which precludes the coordination of base molecules.
Aluminum hydrides with radical-anionic and dianionic acenaphthene-1,2-diimine ligands
Аннотация
The reaction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with LiAlH4 affords two products regardless of the solvent used (tetrahydrofuran or diethyl ether). These products were isolated as green and colorless crystals. Green crystals of the complex [(dpp-bian)Al(H)2Li(THF)3] (1) were obtained from tetrahydrofuran; colorless crystals of the complex [{dpp-bian(H2)}Al(H)2Li(Et2O)2] (2), from diethyl ether. The reactions of compound 1 with 2,6-di-tert-butyl-4-methylphenol and benzophenone gave monohydrides [(dpp-bian)Al(H)(OC6H2-2,6-Bu2t-4-Me)][Li(THF)4] (3) and [(dpp-bian)Al(H)(OCHPh2)- Li(THF)2] (4), respectively. The diamagnetic aluminum hydride [(dpp-bian)AlH(THF)] (5) was synthesized by the reaction of dichloroalane HAlCl2 (in situ) with the disodium salt of dpp-bian in THF; the paramagnetic hydride [(dpp-bian)AlH(Cl)] (6) containing the dpp-bian radical anion was synthesized by the reaction of the monosodium salt (dpp-bian)Na with monochloroalane H2AlCl (in situ) in diethyl ether. The reaction of compound 6 with tert-butyllithium gives the complex [(dpp-bian)AlBut(Et2O)] (7). Diamagnetic derivatives 1—5 and 7 were characterized by 1Н NMR spectroscopy; paramagnetic compound 6, by ESR spectroscopy. The molecular structures of compounds 1—7 were determined by single-crystal X-ray diffraction.
Cadmium(ii) terephthalates based on trinuclear units {Cd3(bdc)3}: control of coordination structure dimensionality and luminescence properties
Аннотация
Two metal-organic coordination polymers based on cadmium(ii) ions and terephthalic (1,4-benzenedicarboxylic) acid were synthesized in dimethylformamide or a mixture of dimethylformamide and methanol: [Cd3(bdc)3(dmf)4] (1, bdc is 1,4-benzenedicarboxylate, dmf is N,N´-dimethylformamide) and [Cd3(bdc)3(dmf)2] (2), respectively. According to the single-crystal X-ray diffraction data, both compounds are built up by the trinuclear carboxylate units {Cd3(O2CR)6}. Compound 1 has a layered structure, whereas compound 2 has a three-dimensional structure due to the presence of additional coordination interactions between adjacent trinuclear units and the formation of polymer chains {Cd3(dmf)2(μ2-O2CR-κ1,κ1)2(μ2-O2CR-κ2,κ1)4(O2CR-κ1)2}. The synthesized compounds were characterized by IR spectroscopy, thermogravimetric analysis, elemental analysis, and powder X-ray diffrac- tion. The luminescence properties of these compounds provide evidence for the existence of both intraligand and charge-transfer transitions. The luminescence quantum yields for both compounds are 10%.
Optically active derivatives of terephthalic acid: synthesis and crystal structures
Аннотация
New optically active derivatives of terephthalic acid, which are of interest as precursors of chiral metal-organic frameworks (MOFs), were synthesized starting from available dimethyl 2-aminoterephthalate, N-Boc-l-alanine, and N-Boc-l-proline. The crystal structures of three samples were determined by powder X-ray diffraction. In all three structures, the acid molecules exist as zwitterions.
Reaction of adamantan-2-amine and (adamantan-1-yl)methylamine with methyl 2-(4-allyl-2-methoxyphenoxy)acetate
Аннотация
A reaction of methyl 2-(4-allyl-2-methoxyphenoxy)acetate with adamantan-2-amine and (adamantan-1-yl)methylamine in butanol leads, together with the target amides, to the formation of butyl ester of the corresponding acid, which is resistant to aminolysis.
Novel olefin metathetis catalysts with fluorinated N-alkyl-N´-arylimidazolin-2-ylidene ligands
Аннотация
Novel ruthenium carbene complexes bearing unsymmetrical NHC-ligands based on N-alkyl-N´-arylimidazoline with hexafluoroisopropylmethoxy group in para-position of N-aryl moiety have been synthesized. Catalytic activity of complexes obtained was investigated on model reactions of intra- and intermolecular olefin metathesis.
Conjugation of indole derivatives by copper-catalyzed alkyne-azide cycloaddition
Аннотация
An efficient synthetic procedure to combine biologically active indole derivatives by the triazole-containing spacer in a molecule has been proposed. The procedure was based on a copper-catalyzed alkyne-azide cycloaddition of azide-containing carbazoles and N-propargyl-containing carbazoles, tetrahydrocarbazoles, and tetrahydro-γ-carbolines.
CuI-catalyzed hetarylation of natural di- and polyamines with halopyridines
Аннотация
Copper(i)-catalyzed hetarylation of natural diamines (putrescine, cadaverine, and hexane-1,6-diamine), their analogs (propane-1,3-diamine and decane-1,10-diamine), as well as natural tri- (spermidine) and tetraamines (spermine) with 2-bromo, 2-iodo-, and 3-iodopyridines was studied. The CuI—2-isobutyrylcyclohexanone (10—20 mol.%) catalytic system provides the best results in the synthesis of target N,N´-dipyridinyl diamine derivatives. In some cases, an increase in the catalyst loading leads to an increase in the yields of the dihetarylated compounds. In the case of tri- and tetraamines, this catalytic system favors the predominant hetarylation of the primary amino groups with 2-bromopyridine and 3-iodopyridine.
Synthesis, structure, and magnetic properties of magnesium bis-3,6-di-tert-butyl-о-benzosemiquinonate complexes with N-donor ligands
Аннотация
A series of six-coordinate magnesium bis-3,6-di-tert-butyl-о-benzosemiquinonate complexes with different N-donor ligands (2,2´-dipyridyl, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, pyridine, N-phenyl-1-(4-pyridinyl)methanimine) were synthesized. The molecular and crystal structures of these complexes were determined by X-ray diffraction. In the complexes with bidentate N-donor ligands, the O,O-diolate o-semiquinone ligands are cis to each other, whereas the compounds with monodentate ligands contain organic radical anions in trans positions. The specific features of magnetic exchange coupling between organic radical ligands were studied by temperature-dependent magnetic susceptibility measurements.
Heterospin biradicals based on new piperidineoxyl-substituted 3,6-di-tert-butyl-o-benzoquinone
Аннотация
A nucleophilic addition reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (OH-TEMPO) to 3,6-di-tert-butyl-o-benzoquinone was used to obtain a new sterically hindered o-benzoquinone (1) containing 2,2,6,6-tetramethylpiperidineoxyl functional group, which was characterized by IR spectroscopy, mass spectrometry, elemental analysis, and X-ray diffraction. A one-electron reduction of 1 with potassium and thallium is an efficient method for the generation of earlier unknown heterospin biradicals 5a and 5b, respectively, containing nitroxide and o-semiquinone radical centers. Analysis of the hyperfine structure of the ESR spectra of biradicals 5a and 5b in solution showed that they belong to the group of heterospin biradicals with strong (J >> a) and fast exchange interaction between the radical centers.
Reaction of benzylidenetriphenylphosphorane with 1,4-dichloro-3а,6а-diaza-1,4-diphosphapentalene
Аннотация
The transylidation between 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalene and benzylidenetriphenylphosphorane (Ph3P=CHPh) results in either mono- or disubstitution of chlorine atoms by the Ph3P=C(Ph) group depending on the reactant molar ratio. In the crystal, the monosubstituted product has the planar diazadiphosphapentalene ring and the P—Cl ionic bond. The 31P NMR spectra of this compound exhibit a strong solvent-dependent behavior, which indicates that it exists both in the ionic form (in CH2Cl2, MeCN) and the molecular form (in THF). In the disubstituted product, the diazadiphosphapentalene skeleton is non-planar and is bent along the N—N bond.
New carborane-containing acids and amines
Аннотация
Alkylation of nido-carborane methyl sulfide derivative [9-MeS-7,8-C2B9H11]– was used to synthesize a series of new carborane-containing acids 9-HOOC(CH2)n(Me)S-7,8-C2B9H11 (n = 1—4) and amines 9-H2N(CH2)n(Me)S-7,8-C2B9H11 (n = 2, 3). The compounds obtained can be used for the development of BNCT agents.
Cobalt and manganese complexes with redox-active ligands in polymerization of acrylonitrile and methyl methacrylate
Аннотация
The influence of bis[4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-iminobenzosemiquinonato]cobalt(ii) and 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinonato]-[4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophenolate]manganese(iii) on polymerization of methyl methacrylate and acrylonitrile in the presence of azobisisobutyronitrile (as a traditional radical initiator) and alkyl halides (used for initiation of controlled atom transfer radical polymerization process) was studied. The effect of the nature of the activating agents (amines) and the temperature conditions on the overall polymerization rate of the indicated monomers, as well as molecular weight characteristics of the synthesized polymers, were analyzed. The optimal conditions for the synthesis of polyacrylonitrile and poly(methyl methacrylate) with a relatively narrow molecular weight distribution were selected.
Specific features of “compensating” copolymerization of butyl acrylate with vinyl butyl ether in the presence of triethylboron
Аннотация
Copolymerization of butyl acrylate with a large excess of boiling vinyl butyl ether was carried out in the presence of triethylborane. The analysis of the composition of the obtained product demonstrated that an alternating low-molecular-weight copolymer was predominantly formed. The formation of macromolecules occurred by both conventional and controlled radical polymerization (CRP), as evidenced by a bimodal molecular weight distribution. As conversion increased, the mode corresponding to the CRP mechanism shifted toward larger molecular masses. The relative activities of comonomers for the process initiated by triethylborane were calculated.
Triketiminate bis(borohydride) complexes of rare-earth metals [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Ln(BH4)2(THF)2 (Ln = Y, Nd): synthesis, structure, and catalytic activity in polymerization of rac-lactide, ε-caprolactone, and isoprene
Аннотация
A new triketimine (2,6-Me2C6H3N=CMe)2CH(2,6-Me2C6H3N=CBut) (1) was synthesized by the reaction of imidoyl chloride 2,6-Me2C6H3N=CClBut with lithium diketiminate (2,6-Me2C6H3N=CMe)2CHLi. In the crystalline state, compound 1 exists in the diimineenamine form; in solution, in the triimine form. The metalation of triketimine 1 with n-butyllithium in THF at 0 °C produced lithium triketiminate [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Li(THF)2 (2). The metathesis reactions of Ln(BH4)3(THF)3 (Ln = Y, Nd) with compound 2 (1: 1 molar ratio, THF) gave the neutral triketiminate bis(borohydride) complexes [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Ln(BH4)2(THF)2 (Ln = Y (3), Nd (4)). As opposed to the complexes with neutral triketimine, the monoanionic triketiminate ligand is coordinated to Li and Y or Nd cations in a bidentate fashion. Complexes 3 and 4 catalyze the polymerization of rac-lactide and ε-caprolactone; in combination with [Ph3C][B(C6F5)4] and AlBu3i (1 : 1 : 10 molar ratio), these compounds exhibit catalytic activity in the polymerization of isoprene.
Synthesis of thioether-containing carbosilane dendrimers with sterically shielded sulfur atoms
Аннотация
Carbosilane thiols were synthesized as the first- and second-generation (in silicon) dendrons. It was demonstrated that the resulting bulky thiols successfully undergo the thiol—ene addition to third-generation polyallyl carbosilane dendrimer as a photoinitiated radical reaction to give the corresponding thioether-containing derivatives with sterically shielded sulfur atoms.
Gas-phase fragmentation studies of biotinylated oligomannuronopyranosides under conditions of collisionally activated dissociation
Аннотация
High-resolution electrospray ionization mass spectra (MS and MS/MS) of a series of glycoconjugates containing biotin and oligomannuronopyranosyl residues linked via a hexaethylene glycol spacer were recorded in the positive and negative ion modes and interpret. In collision activation mass spectra of the positively charged ions (CID MS2), two series of the most abundant peaks were attributed to the fragments resulting from a glycosidic bond cleavage with localization of a charge at either reducing (Y series) or non-reducing end (B series). Fragmentation of hexaethylene glycol chain observed at relatively high activation energies (30 eV or higher) occurred predominantly at the C—O bond most distant from the biotin moiety. In the mass spectra of the negatively charged ions of the studied compounds, the peaks of B, C, and Z series (a systematic nomenclature for carbohydrate fragmentations was used) were present along with the peak analogous to the aforementioned one, which arose from the cleavage of the same C—O bond. The distinctive feature of the fragmentation of the negative ions is the elimination of H2S and H2CS from the biotin moiety.
Disperse aqueous systems based on (S)-lysine in a wide range of concentrations and physiologically important temperatures
Аннотация
It was shown for the first time using a complex of physicochemical methods (dynamic and electrophoretic light scattering, nanoparticle tracking analysis, transmission electron and atomic force microscopy, conductometry, pH-metry) that in a temperature range of 25—60 °С (S)-lysine aqueous solutions (1•10–17—1•10–2 mol L–1) are disperse systems, where the nature and parameters of the disperse phase change with dilution, which affects the nonmonotonic dependences of the specific conductivity and pH of the system. Nanoassociates hundreds of nanometers in size were found to contain ordered water structures that are responsible for the size and ζ-potential of the disperse phase in the aqueous systems and also participate in the formation of spatially organized systems on the support.
Effect of self-organization and properties of aqueous disperse systems based on the moss peptide PpCLE2 in a low concentration range on the growth of Arabidopsis thaliana roots
Аннотация
It is shown for the first time using a complex of physicochemical methods (dynamic and electrophoretic light scattering, conductometry, pH-metry) that below a threshold concentration of 1.0•10–7 mol L–1 the disperse phase of the aqueous systems based on moss peptide PpCLE2 undergoes the domain—nanoassociate rearrangement, which affects the nonmonotonic concentration dependences of the specific electrical conductivity and pH and can result in a multidirectional profile of the dependence of the growth of the primary and lateral roots of the Arabidopsis thaliana seed plant in the range of calculated concentrations from 1.0•10–6 to 1.0•10–12 mol L–1.
Bis(4-nitrobenzenethiolato)tetranitrosyldiiron: synthesis, structure, and pharmacological activity of a new nitric oxide (NO) donor
Аннотация
A preparative procedure was developed for the synthesis of new binuclear tetranitrosyl iron complex of the “μ-S” structural type, [Fe2(SC6H4NO2)2(NO)4] (1), comprising the replacement of the thiosulfate ligands in Na2[Fe2(S2O3)2(NO)4]•4H2O by anions of the 4-nitrobenzenethiolate hydrazinium salt. The salt was obtained by the reduction of bis(4-nitrophenyl) disulfide with hydrazine hydrate in ethanol. The physicochemical properties of the complex in the solid state were studied by IR and Mössbauer spectroscopy. According to amperometric measurements in aqueous solutions, the complex generates NO in a protic medium without additional photo, thermal, or redox activation, providing prolonged release of NO, since the para-positioned nitro group in the aromatic ligand functions as an additional NO source. A study of the pharmacological activity by the MTT assay showed that the complex possesses a high cytotoxic activity against the MCF7 human breast cancer cells (IC50 = 47 μmol L–1) and an antibacterial activity against gram-negative (E. coli, BB strain) and gram-positive (M. luteus, 21/26 strain) microorganisms.
Separation of levoglucosan supramers by high performance liquid chromatography
Аннотация
Analysis of levoglucosan by ligand-exchange chromatography with UV detection showed deviations from the Bouguer—Lambert—Beer law. Their character allowed us to suggest that the deviations are caused by the formation of levoglucosan supramers in the eluent.