Zinc-67 NMR study of zinc ions in water and in some nonaqueous and mixed solvents

Solutions of zinc salts in water, methanol (MeOH), dimethylformamide (DMF) and binary mixtures of water with the two nonaqueous solvents were studied by zinc-67 NMR measurements. Anhydrous zinc nitrate solutions in DMF and MeOH show upfield, concentration independent, chemical shifts at –27 and –19 ppm, respectively, vs. the aqueous solution standard. Addition of DMF or MeOH to an aqueous solution of a zinc salt results in a diamagnetic shift but for the addition of acetonitrile a paramagnetic shift results. In all cases the signal was broadened very considerably, e.g., in ZnCl₂ solution the linewidth increased from 40 to 600 Hz in going from water to 35% aqueous MeOH. Both⁶⁷Zn and¹³C NMR failed to show any complexation of Zn²⁺ ion by crown ethers in aqueous solution. A gradual addition of EDTA, of diaza-18-crown-6 or of tetraazacyclotetradecane resulted in an immediate broadening of the⁶⁷Zn signal which became undetectable when one equivalent of a ligand was added.     

Chelate synthesis of 3-ethoxycarbonyl-4-hydroxy-2-trifluoromethylpyridine from ethyl acetoacetate and trifluoroacetonitrile

Ethyl 2-acetyl-3-amino-4,4,4-trifluoro-2-butenoate was synthesized by treatment of ethyl acetoacetate with CF₃CN in the presence of Ni(acac)₂. Condensation of the diphenylboron chelate of the former with dimethylformamide dimethylacetal followed by refluxing in ethanol yielded 3-ethoxycarbonyl-4-hydroxy-2-trifluoromethylpyridine.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1329–1331, July, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08964).     

Efficient DMF‐Promoted Solventless Hydrolysis of Epoxides with Equimolar Amount of H2O,Affording 1,2‐Diols

A mild and efficient N,N‐dimethylformamide (DMF)–catalyzed solvent‐free hydrolysis of epoxides with an equimolar amount of H₂O to afford 1,2‐diols in good to excellent yields has been developed.     

Chelate synthesis of 8-diaminomethylene-5,6,7,8-tetrahydroquinazoline-7-one derivatives

A scheme for synthesizing 5,6,7,8-tetrahydroquinazoline systems from ketene aminal1 via its diphenylboron chelate2 has been suggested. The interaction ofp-toluamidine with the condensation product of the chelate with dimethylformamide dimethylacetal results in the formation of 8-(N-benzoyldiaminomethylene)-2-p-tolyl-5,6,7,8-tetrahydroquinazoline-7-one, which is easily debenzoylated by sodium ethoxide. 8-Diaminomethylene-5,6,7,8-tetrahydroquinazolinone derivatives can be used for the preparation of boron chelate complexes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 888–890, May, 1994.     

Mobilities of complex forming cations in non-aqueous donor solvents

Conductance measurements are reported for Al(ClO₄)₃ in acetonitrile Co(ClO₄)₂, Zn(ClO₄)₂, and Al(ClO₄)₃ in dimethylformamide, and Al(ClO₄)₃, Fe(ClO₄)₃, and FeCl₃ in dimethylsulfoxide (DMSO), at 25°C. From uv spectral effects the FeCl (DMSO) ₅ ²⁺ complex cation is shown, to predominate in DMSO, while hexasolvated cations occur in the metal perchlorate solutions. The limiting conductances of the cations, including earlier data, indicate non-Stokesian dependences of mobility on the ionic charge, a unique property of the structurally related complex ions ML ₆ ^z+ and MXL ₅ ^(z–1)+ . The observed regularities are discussed in terms of both their possible applications and the migration mechanism.     

Freezing temperatures of aqueous solutions of mixtures of amides and polyols. Gibbs energy of interaction of the amide group with the hydroxyl group in aqueous solution

Freezing temperatures of dilute aqueous mixtures of: formamide with myo-inositol, d-mannitol, and cyclohexanol; N,N-dimethylformamide with inositol, mannitol, and cyclohexanol; and acetamide with inositol and mannitol have been measured. These data have been analyzed to yield the pairwise molecular Gibbs energies of interaction between the molecules in an aqueous solution. Using the group additivity principle, the results yield the pairwise functional group Gibbs energies of interaction of the amide group with the hydroxyl group, G _OH,CONH =–31 J-kg-mol^–2.     

DMA水溶液的1H NMR研究

测量了N,N-二甲基乙酰胺(DMA)水溶液体系不同温度下全浓度范围的¹H NMR数据, 对体系中的缔合情况进行了讨论, 应用化学缔合模型求得了各缔合平衡常数K和缔合平衡的ΔH. 结合N,N-二甲基甲酰胺(DMF)和N-甲基乙酰胺(NMA)水溶液的研究结果, 发现酰胺自身结构和酰胺浓度是影响酰胺水溶液性质的主要因素.     

The synthesis and coordination chemistry of 2,6-bis(pyrazolyl)pyridines and related ligands — Versatile terpyridine analogues

Derivatives of 2,6-di(pyrazol-1-yl)pyridine and 2,6-di(pyrazol-3-yl)pyridine have been used as ligands for 15 years, and have both advantages and disadvantages in this regard compared to the much more widely investigated terpyridines. A review of the synthesis of these and some related ligand types, and a survey of their complex chemistry, are presented. Highlights of the latter include luminescent lanthanide compounds for biological sensing, and iron complexes showing unusual thermal and photochemical spin-state transitions.