Showing papers in "Russian Chemical Bulletin in 2006"
TL;DR: In this article, the results of systematic X-ray diffraction studies of the electron density distribution in the crystals of compounds with strong intramolecular hydrogen bonds N-H...O, O-H...O, N- H...N, and N H...S are discussed.
Abstract: The review concerns the results of systematic X-ray diffraction studies of the electron density distribution in the crystals of compounds with strong intramolecular hydrogen bonds N-H...O, O-H...O, O-H...N, and N-H...S. The advantages of the topological analysis of the electron density distribution function in the analysis of the nature and estimation of the H-bond energies directly from experimental data are discussed.
49 citations
TL;DR: The [{Pr(NO3)2(H2O)3}{Pr( NO3)3·4H 2O and [{Nd(NO 3)(H 2 O)4} 2(NO(@C36H36N24O12)][Nd[NO3]6] complexes were prepared by heating a mixture of lanthanide nitrates, cucurbit[6]uril, and water in a sealed tube, and X-ray diffraction study demonstrated that the metal atoms in the former complex are linked to the
Abstract: The [{Pr(NO3)2(H2O)3}{Pr(NO3)(H2O)4} (C36H36N24O12)](NO3)3·4H2O and [{Nd(NO3)(H2O)4} 2(NO3@C36H36N24O12)][Nd(NO3)6] complexes were prepared by heating a mixture of lanthanide nitrates, cucurbit[6]uril, and water in a sealed tube. X-ray diffraction study demonstrated that the metal atoms in the former complex are linked to the macrocycle through tridentate coordination of the portal oxygen atoms of cucurbit[6]uril to the praseodymium(III) cation. The neodymium(III) complex is the first example of lanthanide compounds with cucurbit[6]uril belonging to coordination polymers.
47 citations
TL;DR: In this article, the photochemical chlorination of nanodiamond by molecular chlorine in the liquid phase was studied quantitatively for the first time and a possibility of disintegration of the initial aggregates (<60 µm) to finer aggregates <200 nm was shown.
Abstract: A procedure for the photochemical chlorination of nanodiamond by molecular chlorine in the liquid phase was proposed. This process was studied quantitatively for the first time. Hydrolytic stability of the chlorinated nanodiamond surface in air and in a 0.05 M solution of NaOH was determined. A possibility of disintegration of the initial aggregates (<60 µm) to finer aggregates (<200 nm) was shown. The reactions of a series of C-nucleophiles (organolithium reagents, CN− ion) with the chlorinated surface were carried out.
39 citations
TL;DR: A coordination polymer of the general formula [Co(OOCCMe3)2]n (2) was prepared by mild thermolysis of the coordination polymers of variable composition as discussed by the authors.
Abstract: A coordination polymer of the general formula [Co(OOCCMe3)2]n (2) was prepared by mild thermolysis of the coordination polymer of variable composition [(HOOCCMe3)xCo(OH)n(OOCCMe3)2−n
]m, the dinuclear cobalt complex Co2(μ-H2O)(OOCCMe3)4(HOOCCMe3)4, the tetranuclear cobalt cluster Co4(μ3-OH)2(OOCCMe3)6(HOEt)6, and the hexanuclear cluster [Co6(μ4-O)2(μn-OOCCMe3)10(C4H8O)3(H2O)]·1.5(C4H8O) (7) in organic solvents. In the crystal, the polymer has a chain structure. Unlike thermolysis of cobalt pivalates, thermolysis of the dinuclear complex Ni2(μ-H2O)(OOCCMe3)4(HOOCCMe3)4 gave rise to the hexanuclear complex Ni6(μ2-OOCCMe3)6(μ3-OOCCMe3)6 (3). The magnetic properties of compound 2 are substantially different from those of 3. Compound 2 undergoes the magnetic phase transition into the ordered state at T
c = 3.4 K (H = 1 Oe), whereas compound 3 exhibits antiferromagnetic properties. Solid-state decomposition of polymeric cobalt carboxylate 2 (below 350 °C) afforded the octanuclear cluster Co8(μ4-O)2(μ2-OOCCMe3)6(μ3-OOCCMe3)6 (9) as the major product, which sublimes without decomposition. Decomposition of 3 gave nickel oxide as the final product. Pivalates 2 and 3 reacted with 2,3-lutidine in acetonitrile at 80 °C to form the isostructural dinuclear complexes (2,3-Me2C5H3N)2M2(μ-OOCCMe3)4 (M = Co or Ni). The structures of compounds 3 and 7 were established by X-ray diffraction. The structure of polymer 2 was determined by powder X-ray diffraction analysis.
39 citations
TL;DR: In this article, spontaneous photochemical trans-cis isomerization of cross-conjugated dienones under the scattered light in solution was observed for the first time.
Abstract: Cross-conjugated dienones were synthesized by the reactions of cyclic ketones with two equivalents of aromatic aldehydes under basic conditions. An NMR spectroscopic study and X-ray diffraction analysis demonstrated that all reaction products are formed as E,E isomers. Spontaneous photochemical trans-cis isomerization of cross-conjugated dienones under the scattered light in solution was observed for the first time. The degree of isomerization depends mainly on the nature of the central fragment of the dienone molecule. The previously unknown product of photochemical [2+2]-cycloaddition of 2,5-bis[(E)-(3-pyridyl)methylidene]cyclopentanone was synthesized and characterized by spectroscopic methods and X-ray diffraction. Under the conditions used, only one isomer of the cyclobutane adduct was obtained.
36 citations
TL;DR: In this paper, the metathesis reaction of the magnesium complex (dpp-BIAN)2−Mg2+(THF)3] with one equivalent of AlCl3 in toluene gave the [(dpp]-BIAN]2−AlCl2]−[Mg 2Cl3(THF6]+ complex (1).
Abstract: The metathesis reaction of the magnesium complex [(dpp-BIAN)2−Mg2+(THF)3] (dpp-BIAN is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with one equivalent of AlCl3 in toluene gave the [(dpp-BIAN)2−AlCl2]−[Mg2Cl3(THF)6]+ complex (1). Reduction of dpp-BIAN with aluminum metal in the presence of AlCl3 and AlI3 in toluene and diethyl ether afforded the radical-anionic complex [(dpp-BIAN)−AlCl2] (2) and the dianionic complexes [(dpp-BIAN)2−AlI(Et2O)] (3) and [(dpp-BIAN)2−AlCl(Et2O)] (4), respectively. Compounds 1–4 were isolated in the crystalline state and characterized by IR spectroscopy and elemental analysis. The structures of compounds 1–3 were established by X-ray diffraction. Compound 2 was characterized by ESR spectroscopy. Compounds 3 and 4 were studied by 1H and 13C NMR spectroscopy.
32 citations
TL;DR: The tetradentate coordination of the macrocyclic cucurbit[6]uril ligands through the portals leads to the formation of sandwich compounds, in which the tetranuclear hydroxo complex is located between two microcyclic molecules as discussed by the authors.
Abstract: The tetranuclear lanthanide complexes {[Ln4(μ3-OH)4(μ2-OH)2(C5NH4COO)2 (H2O)4-(C36H36N24O12)2][Ln(H2O)8]1.5[Ln(H2O)6(NO3)2]0.5} (NO3)9·nH2O (Ln = Ho, Gd, or Er) were prepared by heating (130 °C) aqueous solutions of lanthanide nitrates, cucurbit[6]uril (C36H36N24O12), and 4-cyanopyridine. The tetradentate coordination of the macrocyclic cucurbit[6]uril ligands through the portals leads to the formation of sandwich compounds, in which the tetranuclear hydroxo complex is located between two macrocyclic molecules. The polynuclear complexes are additionally stabilized by the chelating effect of the isonicotinate ligands generated by hydrolysis of 4-cyanopyridine. In the complexes, the aromatic moiety of the isonicotinate ion is encapsulated into the hydrophobic inner cavity of cucurbit[6]uril. In the absence of cucurbit[6]uril, the reaction with 4-cyanopyridine produces only the polymeric complexes [Nd(C5NH4COO)3(H2O)2] and [Ln(C5NH4COO)2(H2O)4]NO3 (Ln = Pr, Sm, or Gd), whose structures were established by X-ray diffraction. In water and aqueous solutions of nonionic and cationic surfactants, irreversible changes of the tetranuclear fragment of the complex (Ln = Gd) were observed after storage for two days, whereas the anionic surfactant stabilizes the complexes.
31 citations
TL;DR: In this article, a new molecular orbital diagram for bond formation is proposed, which takes into account the interaction of all five substituents at the central atom (M = Si, Ge) in atrane molecules.
Abstract: Molecular geometries of fifty-six metallatranes N(CH2CH2Y)3M-X and fifty-six carbon analogs HC(CH2CH2Y)3M-X (M = Si, Ge; X = H, Me, OH, F; Y = CH2, O, NH, NMe, NSiMe3, PH, S) were optimized by the DFT method. Correlations between changes in the bond orbital populations, electron density ρ(r), electron density laplacian ∇2ρ(r), ¦λ1¦/λ3 ratio, electronic energy density E(r), bond lengths, and displacement of the central atom from the plane of three equatorial substituents and the nature of substituents X and Y were studied. As the number of electronegative substituents at the central atom increases, the M←N, M-X, and M-Y bond lengths decrease, while the M←N bond strength and the electron density at critical points of the M←N, M-X, and M-Y bonds increase. An increase in electronegativity of a substituent (X or Y) is accompanied by a decrease in the ionicities of the other bonds (M-X, M-Y, and M←N) formed by the central atom (Si, Ge). A new molecular orbital diagram for bond formation is proposed, which takes into account the interaction of all five substituents at the central atom (M = Si, Ge) in atrane molecules.
30 citations
TL;DR: In this article, X-ray diffraction study demonstrated that the aqua hydroxo complexes are linked to the macrocycle through hydrogen bonds between the hydroxos and aqua ligands of the polycations and the portal oxygen atoms of cucurbit[6]uril.
Abstract: Supramolecular compounds of the di-, trideca-, and triacontanuclear aluminum aqua hydroxo complexes, viz., [Al2(OH)2(H2O)8]4+, [Al12(AlO4)(OH)24(H2O)12]7+, and [Al30O8(OH)56(H2O)26]18+, respectively, with the organic macrocyclic cavitand cucurbit[6]uril (C36H36N24O12) were prepared by evaporation of aqueous solutions of aluminum nitrate and cucurbit[6]uril after the addition of pyridine, ammonia, KOH, or NaOH at pH 3.1–3.8. X-ray diffraction study demonstrated that the aqua hydroxo complexes are linked to the macrocycle through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of cucurbit[6]uril.
27 citations
TL;DR: In this article, a representative of a new family of xyloketals, was isolated from the marine-derived mangrove fungus Xylaria sp. 2508 and its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction analysis.
Abstract: (3R*,3aR*,9aR*)-3,9a-Dimethyl-2,3,3a,9a-tetrahydro-4H-furo[2,3-b]chromene-5,7-diol (xyloketal H), a representative of a new family of xyloketals, was isolated from the marine-derived mangrove fungus Xylaria sp. 2508. Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction analysis.
26 citations
TL;DR: The structure of conjugated dienyl sulfides formed in the reaction was determined by 2D NMR spectroscopy as mentioned in this paper. But the structure of the sulfide was not analyzed.
Abstract: Nickel-catalyzed addition of benzenethiol to alkynes leads to alkenyl and dienyl sulfides; the direction of the process can be controlled by varying the PhSH/alkyne ratio. An advanced procedure, which ensures higher yields of 2-phenylsulfanylalkenes, includes gradual addition of alkyne to the other reactants. The structures of conjugated dienyl sulfides formed in the reaction were determined by 2D NMR spectroscopy.
TL;DR: In this paper, the molecular structure of the (CatPb)4·(PbO)2·6C3H6O complex (Cat is the dianion of 3,6-di-tert-butylcatechol) was established by X-ray diffraction.
Abstract: Lead(II) catecholate complexes were prepared by reduction of 3,6-di-tert-butyl-o-benzoquinone and its derivatives with lead metal in THF. The molecular structure of the (CatPb)4·(PbO)2·6C3H6O complex (Cat is the dianion of 3,6-di-tert-butylcatechol), which was synthesized by hydrolysis of lead 3,6-di-tert-butylcatecholate in acetone, was established by X-ray diffraction. A series of lead(II) o-semiquinone complexes, which were prepared by the addition of the phenoxyl radical to lead catecholates or by oxidation of the latter with mercury(II), copper(II), or silver(I) halides, were studied by the ESR method. Lead(II) mono-o-semiquinolate complexes undergo symmetrization to form stable bis-o-semiquinolates, which were isolated and characterized in individual state.
TL;DR: In this article, the role of metal centers in controlling the synthesis of 2,3-dihydro-1,2,4-oxadiazoles is discussed.
Abstract: Data on 1,3-dipolar cycloaddition of nitrones to free and coordinated nitriles producing 2,3-dihydro-1,2,4-oxadiazoles (or Δ4-1,2,4-oxadiazolines) are summarized. The latter compounds belong to the virtually unknown class of heterocyclic systems. The main factors responsible for the cycloaddition reactions are discussed. Particular attention is given to the role of metal centers in controlling the synthesis of 2,3-dihydro-1,2,4-oxadiazoles.
TL;DR: Chiral coordinatively saturated cobalt(III) complexes with Schiff bases of enantio-pure amino acids are formed as Λ and Δ-isomers, which are not transformed into each other under normal conditions as discussed by the authors.
Abstract: Chiral coordinatively saturated cobalt(III) complexes with Schiff bases of enantio-pure amino acids are formed as Λ and Δ-isomers, which are not transformed into each other under normal conditions. These complexes catalyze the formation of enantiomerically enriched cyanohydrins from aldehydes and Me3SiCN under homo-and heterogeneous catalysis.
TL;DR: In this article, an analysis of the influence of the nature of the imidazolium cation on the formation of a hydrogen bond system and the supramolecular arrangement of ions demonstrated that not only CH⋯Br contacts but also anion-π-system and CH-π system interactions exist in the crystalline state.
Abstract: Systematic X-ray diffraction study of the crystal structures of 1,3-dialkylimidazole-based ionic liquids containing the Br− anion was performed. Analysis of the influence of the nature of the cation on the formation of a hydrogen bond system and the supramolecular arrangement of ions demonstrated that not only CH⋯Br contacts but also anion—π-system and CH—π-system interactions exist in the crystalline state. Conclusions were drawn on the character of changes in the melting point in a series of bromide ionic liquids containing the imidazolium cation.
TL;DR: In this article, it was shown that ligand 1 stabilizes reduced forms of 2-(2-pyridyl)benzothiazole complexes with Ni, Co, or Cu atoms in the oxidation state + 1.
Abstract: The reactions of 2-(2-pyridyl)benzothiazole (1) with MX2·nH2O salts (M = NiII, CoII, or CuII; X = Cl or ClO4; n = 0–2) in EtOH afforded the corresponding complexes. Depending on the nature of the counterion in the starting metal salt, the reactions give compounds of composition M(1)Cl2·nH2O or Cu(1)2(ClO4)2·H2O. The molecular and crystal structure of the CuII(1)2(ClO4)2·H2O complex was established by X-ray diffraction. The copper atom in this complex has a distorted tetragonal-pyramidal ligand environment and is coordinated by four nitrogen atoms of two ligand molecules and one water molecule. Electrochemical study of the ligand and the resulting complexes by cyclic voltammetry and at a rotating disk electrode demonstrated that ligand 1 stabilizes reduced forms of complexes containing Ni, Co, or Cu atoms in the oxidation state +1.
TL;DR: In this paper, a new method was developed for the synthesis of functionalized β-tropolones based on acid-catalyzed condensation of 2-methylquinoline derivatives with 3,5-di(tert-butyl)-1,2-benzoquinone and 4,6-dioxo-2-azabicyclo[3.3.0]octa-2,7-diene Noxide.
Abstract: A new method was developed for the synthesis of functionalized β-tropolones based on acid-catalyzed condensation of 2-methylquinoline derivatives with 3,5-di(tert-butyl)-1,2-benzoquinone and 4,6-di(tert-butyl)-3-nitro-1,2-benzoquinone (14). The mechanism of the multistep reaction giving rise to β-tropolones and their tautomerism were studied by quantum chemical methods (DFT B3LYP/6-31G**). The reaction of 2-methylquinoline derivatives containing the tertiary amino group at position 4 with quinone 14 is accompanied by the formation of derivatives of a new heterocyclic system, viz., 4,6-dioxo-2-azabicyclo[3.3.0]octa-2,7-diene N-oxide. The molecular and crystal structures of two 5,7-di(tert-butyl)-3-hydroxy-2-(quinolin-2-yl)tropolones and two dioxoazabicyclooctadiene N-oxides, as well as of the preparatively isolated intermediate of the first condensation step and of the by-product of the reaction were established by X-ray diffraction.
TL;DR: In this paper, a facile preparative procedure was developed for the synthesis of 17 and 18-electron closo-(diphosphine)ruthenacarborane complexes.
Abstract: A facile preparative procedure was developed for the synthesis of 17-and 18-electron closo-(diphosphine)ruthenacarborane complexes. This method is based on the replacement of PPh3 ligands with bis(diphenylphosphino)alkanes Ph2P(CH2)nPPh2 (n = 2—4) in ruthenacarborane 3,3-(PPh3)2-3-Cl-3-H-closo-3,1,2-RuC2B9H11. The resulting complexes exhibit high activity in controlled radical polymerization of vinyl monomers.
TL;DR: In this paper, the most favorable thermal decomposition pathways of nitrotriazoles were assessed using the density functional approach (B3LYP/6-31G* approximation), and the relationship between the thermolysis pathways of these substances and their molecular and electronic structures was studied.
Abstract: Possible decomposition mechanisms of C-nitro-and N-nitro-1,2,4-triazoles were simulated. We showed that in addition to the experimentally detected thermolysis products including N2, N2O, NO, CO2, HCN, HNCO, 1,2,4-triazole, 3(5)-nitroso-1,2,4-triazole, and 1,2,4-triazolone, some other decompositon products (H2O, CO, NO2, cyanamide, cyanuric acid, and melamine) can be formed. Using the density functional approach (B3LYP/6-31G* approximation), we assessed the most favorable thermal decomposition pathways of nitrotriazoles and studied the relationships between the thermolysis pathways of these substances and their molecular and electronic structures. We found a correlation between the energy gap width (energy difference between the frontier molecular orbitals) and the stabilities of the C-nitro-1,2,4-triazole tautomers to thermal decomposition.
TL;DR: In this paper, new initiators based on closo and exo-nido-ruthenacarboranes with phosphine and diphosphine ligands were proposed as chain growth regulators.
Abstract: New initiators based on closo-and exo-nido-ruthenacarboranes with phosphine and diphosphine ligands were proposed as chain growth regulators. They allow conducting the controlled synthesis of poly(methyl methacrylate) under radical initiation conditions.
TL;DR: In this article, the influence of the nature of a metal (Li, Na, K) on the formation of the pentaphosphacyclopentadienide anion was studied.
Abstract: Heating of a mixture of white phosphorus and sodium in diethylene glycol dimethyl ether in the presence of catalytic amounts of dibenzo-18-crown-6 affords a pure solution of sodium pentaphosphacyclopentadienide NaP5. One of the intermediate products is trisodium heptaphosphide Na3P7. The influence of the nature of a metal (Li, Na, K) on the formation of the pentaphosphacyclopentadienide anion was studied.
TL;DR: In this paper, a new five-coordinate complexes Co(ISQ-Pri)2Cl, Co(IsQ-Me)2C2C and Co(isQ-me)2D2C were synthesized and characterized by UV-Vis and IR spectroscopy.
Abstract: New five-coordinate complexes Co(ISQ-Pri)2Cl, Co(ISQ-Me)2Cl, Co(ISQ-Me)2I, Co(ISQ-Me)2(SCN), Mn(ISQ-Pri)2Cl, and Fe(ISQ-Me)2Br (ISQ-Pri and ISQ-Me are the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-and 4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-iminobenzosemiquinone radical anions, respectively) were synthesized. The complexes were characterized by UV-Vis and IR spectroscopy and magnetochemistry. The molecular structures of the Fe(ISQ-Me)2Br and Mn(ISQ-Pri)2Cl complexes were established by X-ray diffraction. The singlet ground state (S = 0) of the cobalt complexes is caused by antiferromagnetic coupling between the unpaired electrons of the radical ligands (S = 1/2) through the fully occupied atomic orbitals of low-spin cobalt(III) (d6, S = 0). The effective magnetic moments of the complexes at 10 K are 0.18 μB for Co(ISQ-Pri)2Cl and 0.16 μB for Co(ISQ-Me)2I. The ground state of the manganese complex is triplet (S = 1). Two unpaired electrons of the o-iminobenzosemiquinone ligands are strongly antiferromagnetically coupled with two of four unpaired electrons of high-spin manganese(III) (d4, S = 2).
TL;DR: In this paper, a reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate, the halogen atom was replaced by the ethyl Xanthate group.
Abstract: In a reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate, the halogen atom was replaced by the ethyl xanthate group. Acid hydrolysis of the product gave 4,7-di(tert-butyl)-5,6-dihydroxy-1,3-benzodithiol-2-one containing a pyrocatechol fragment, which was oxidized into the corresponding quinone. When irradiated in solution with visible light, this quinone quantitatively eliminated a CO molecule with contraction of the ring to a five-membered one. The quinones obtained were studied as ligands in coordination spheres of metals by ESR spectroscopy.
TL;DR: In this paper, the authors measured the heats of dissolution of tetramethyl-bis-carbamide (the pharmaceutical Mebicarum) in H2O and D2O at 288.15, 298.15 and 318.15 K using a sealed microcalorimeter with an isothermal shell.
Abstract: The heats of dissolution of tetramethyl-bis-carbamide (the pharmaceutical Mebicarum) in H2O and D2O were measured at 288.15, 298.15, and 318.15 K using a sealed microcalorimeter with an isothermal shell. The error of measurements did not exceed 0.2%. The limiting molar enthalpies of dissolution Δsol
H
n
∞ and the H/D-isotope enthalpy effects of hydration δΔhydr
H
n
∞(H2O → D2O) were determined. Different effects of temperature on the pattern of variation of δΔ hydr
H
n
∞ were found: when T ≤ 315 K, this value is positive and decreases with T, while for T ≥ 315 K, hydration of tetramethyl-bis-carbamide upon replacement of H2O by D2O progressively becomes less endothermic.
TL;DR: In this paper, the reactions of carbocyclic, hetercyclic, and steroidal ketones with benzylamine and diethyl phosphite in a catalytic three-component one-pot synthesis of α-amino phosphonates were studied.
Abstract: Reactions of carbocyclic, heterocyclic, and steroidal ketones with benzylamine and diethyl phosphite in a catalytic three-component “one-pot” synthesis of α-amino phosphonates were studied. The activities of mono-and binuclear complexes of tetra(tert-butyl)phthalocyanines as catalysts for this process were compared.
TL;DR: In this paper, the reactions of tin(II) and antimony(III) chlorides with dtb-bi-isopropylphenyl)imino]acenaphthene were studied by ESR spectroscopy.
Abstract: Reactions of diimines dtb-BIAN and dph-BIAN with GeCl2 afford germanium(II) complexes with radical-anionic ligands, (dtb-BIAN)GeCl (5) and (dph-BIAN)GeCl (6a), respectively, where dtb-BIAN is 1,2-bis[(2,5-di-tert-butylphenyl)imino]acenaphthene and dph-BIAN is 1,2-bis[(2-biphenyl)imino]acenaphthene. The latter reaction gives 6a along with [(dph-BIAN)GeCl]+[GeCl3]− (6b). The reactions of tin(II) and antimony(III) chlorides with dtb-BIAN and dpp-BIAN produce complexes of these halides with neutral coordinated diimines, viz., (dtb-BIAN)SnCl2 (7) and (dpp-BIAN)SbCl3 (8) (dpp-BIAN is 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene). Paramagnetic complexes 5 and 6a were studied by ESR spectroscopy. Diamagnetic compounds 7 and 8 were characterized by 1H NMR spectroscopy. The structures of complexes 5, 6a,b, 7, 8, and (dpp-BIAN)Ge (9) were established by X-ray diffraction analysis.
TL;DR: In this paper, the insertion of N,N′-dicyclohexyl carbodiimide at one of the Y-N bonds of the [(Me3Si)2N]3Y complex in toluene at 70 °C afforded the monoguanidinate diamide derivative { (Me 3Si2NC(N-cyclo-Hex)2}Y[N(SiMe)3]2 ) in 72% yield.
Abstract: The insertion of N,N′-dicyclohexylcarbodiimide at one of the Y-N bonds of the [(Me3Si)2N]3Y complex in toluene at 70 °C afforded the monoguanidinate diamide derivative { (Me3Si)2NC(N-cyclo-Hex)2}Y[N(SiMe)3]2 (1) (cyclo-Hex is cyclohexyl) in 72% yield. The reaction of equimolar amounts of sodium N,N′-dicyclohexyl-N″-bis(trimethylsilyl)guanidinate, which was prepared in situ from {(Me3Si)2N}Na and N,N′-dicyclohexylcarbodiimide, and YbI2(THF)2 in THF gave the [{(Me3Si)2NC(N-cyclo-Hex)2}YbI(THF)2]2 complex (2). An attempt to use this procedure for the synthesis of the yttrium compound { (Me3Si)2NC(NSiMe3)2}2YCl containing the sterically more hindered guanidinate ligand unexpectedly led to the formation of the diamide chloride complex [{(Me3Si)2N}2Y(THF)(µ-Cl)]2 (3). The structures of complexes 1–3 were established by X-ray diffraction. Compound 1 is mononuclear. Complexes 2 and 3 are dinuclear and contain two µ2-bridging halide ligands.
TL;DR: In this article, the reactions of 3-nitro-2-trifluoromethyl-2H-chromenes with thiols and aromatic amines proceed via the nucleophilic addition type to the activated double bond.
Abstract: The reactions of 3-nitro-2-trifluoromethyl-and 3-nitro-2-trichloromethyl-2H-chromenes with thiols and aromatic amines proceed via the nucleophilic addition type to the activated double bond to form 2,3,4-trisubstituted chromanes in high yields. The stereoisomeric compositions and structures of the diastereomers were determined by 1H, 19F NMR and 2D NOESY spectroscopies and X-ray diffraction analysis.
TL;DR: In this article, a series of CuII, NiII, and CoII complexes with 5-(pyridylmethylidene)-substituted 2-thiohydantoins (L) were synthesized by the reactions of the corresponding organic ligands with MCl2·nH2O.
Abstract: A series of CuII, NiII, and CoII complexes with 5-(pyridylmethylidene)-substituted 2-thiohydantoins (L) were synthesized by the reactions of the corresponding organic ligands with MCl2·nH2O. The resulting complexes have the composition LMCl2 (M = Cu or Ni) or L2MCl2 (M = Co). The reactions with N(3)-unsubstituted thiohydantoins afford complexes containing four-membered metallacycles, in which the metal ion is coordinated by the S and N(3) atoms of the thiohydantoin ligand. The reactions of N(3)-substituted thiohydantoins give complexes in which the S and N(1) atoms are involved in coordination. Study by IR spectroscopy demonstrated that the pyridine nitrogen atom is not involved in coordination. Based on the results of electrochemical study of the ligands and complexes by cyclic voltammetry and calculation of their frontier orbitals by the PM3(tm) method, the mechanism of oxidation and reduction of these compounds was proposed. In the first reduction and oxidation steps, the metal atom in the copper and nickel complexes remains, apparently, intact, and these processes occur with the involvement of the ligand fragments, viz., the coordinated thiohydantoin ligand and chloride anion, respectively. In the cobalt complexes, the first reduction step occurs at the ligand; the first oxidation state, at the metal atom. Measurements of the contact angle of aqueous wetting and electrochemical study demonstrated that carboxy-containing 2-thiohydantoins and their complexes can be adsorbed on the cystamine-modified gold surface. The structures of the complexes on the surface differ from the structures of these complexes in solution.