Synthesis and electronic,magnetic and E.s.r. studies of some bimetallic alkoxides of copper(II) with niobium(V) and Tantalum(V)

Summary Novel bimetallic alkoxides of copper(II) of the type Cu[M(OPr-i)₆]₂ (M = Nb or Ta) have been synthesised by the interaction of CuCl₂ (1 mol) with K[M(OPr-i)₆] (2 mol). These bimetallic isopropoxides undergo facile alcohol interchange with primary alcohols such as MeOH, EtOH,n-PrOH andn-BuOH. However, witht-BuOH, the reaction cannot be driven to completion even under prolonged continuous azeotropic fractionation of the liberatedi-PrOH and the final product corresponded in analysis to Cu[Ta(OPr-i)₂(OBu-t)₄]₂.I.r., electronic and electron spin resonance spectral and magnetic susceptibility measurements indicate a distorted octahedralD _4h geometry for copper(II) in these bimetallic alkoxides.     

Polymerization of cyclohexene oxide with aluminum complex-silanol catalyst. IV. Photopolymerization with Ph3SiCOPh-Al complex-alcohol catalyst system

A new catalyst system (Ph₃SiCOPh-aluminum complex-alcohol) was investigated for photopolymerization of cyclohexene oxide. Polymer conversion and molecular weight increased with polymerization time. When a Ph₃SiCOPh-Al (n-Praa)₃-alcohol catalyst system was used the catalyst activity decreased, depending on the alcohol: i-PrOH > n-PrOH > i-BuOH > MeOH > t-BuOH > H₂O. When the Ph₃SiCOPh-Al complex-i-PrOH catalyst system was used the catalyst activity decreased, depending on the ligand of the Al complex: ß-ketoester > orthocarbonyl phenol > ß-diketone. Benzophenone derivatives were effective for catalyst activation as a photosensitizer.     

Reactions of nanoparticles inside a polyethylene matrix: Reduction of lead(II) and mercury(II) oxides by supercritical isopropanol

Methods were developed for manufacturing of isolated nanoparticles of lead(II) and mercury(II) oxides produced by the thermal decomposition of metal compounds in a solution-melt of low-density polyethylene (LDPE) in mineral oil. The PbO and HgO nanoparticles stabilized in the LDPE matrix were characterized using X-ray powder diffraction and transmission electron microscopy (TEM). The metal oxides in the polyethylene matrix were reacted with a supercritical fluid of isopropanol (SCF i-PrOH). The PbO in the nanoparticles was reduced to the metal as a result of the reaction with SCF i-PrOH. When SCF i-PrOH was reacted with the HgO nanoparticles stabilized in the LDPE matrix, the oxide was also reduced to the metal. TEM showed that the nanoparticles were conserved after their reaction with SCF i-PrOH.     

Direct observation of hydrophobic interactions in aqueous solutions of organic compounds by supercooling and enthalpies of mixing

Supercooling temperatures and enthalpies of mixing with some solvents have been examined for two kinds of solutions subjected to different thermal treatments (solutions I and II) of tetrahydrofuran (THF), isopropyl alcohol (2-PrOH), and ethyleneglycol butylether (BE), and ethyleneglycol isobutylether (i-BE) in order to observe more directly the structural organization of water molecules around a nonpolar molecule in an aqueous solution. For THF and 2-PrOH solutions, supercooling temperatures of solution I were found to be 2–3 degrees higher than those of solution II, and differences H_I-H_II were found to be about 3 kJ mol^–1. It has been concluded that these results directly reflect the difference in the stability of hydrogen-bonded water networks in an aqueous solution.     

Spectroscopic investigations of C3 primary alcohols on platinum electrodes in acid solutions.: Part I. n-propanol

The electrochemical behavior of n-propanol (n-PrOH) on polycrystalline Pt in acid solutions was investigated using in situ Fourier transform infrared spectroscopy (FTIRS) and on line differential electrochemical mass spectrometry (DEMS). The main products of n-PrOH oxidation are CO₂, propanal and propionic acid. Different types of adsorbates with one, two or three C atoms were detected. Ethane and propane are produced from n-PrOH adsorbates during potential cycling in the H-adatom potential region. An increase in the quantity of adsorbed CO was observed after hydrogenation of n-PrOH adsorbates.     

Spectrophotometric investigation of nickel(II) chloro complexes in alcoholic solutions

Summary A spectrophotometric study of Ni^II chloro complexes in the u.v.-vis. region was carried out at 25 °C and constant ionic strength of 1 mol dm^–3. A matrix rank treatment method was used to identify two successive mononuclear complexes, NiCl⁺ and NiCl₂, in the three alcohols studied viz. MeOH, EtOH and i-PrOH. The best values for the apparent overall stability constants, _j , were calculated using a program based on the least-squares method. The log ₁ and log ₂ values in MeOH, EtOH and i-PrOH are 1.3 and 1.2, 1.7 and 1.8, and 1.9 and 2.2, respectively. The stability increases directly with the mol. wt. of the solvent, or decreases as a linear function of the permittivity of the pure solvent. The electronic spectra and the formation curves of the two complexes in MeOH solutions were calculated.     

Untersuchungen über Zinn(IV)-alkoxide. I Kristall- und Molekülstruktur des Zinn(IV)-isopropanolat-Isopropanolsolvats,Sn(OiPr)4 · i-PrOH

Investigations into Tin(IV) Alkoxides. I. Crystal and Molecular Structure of Tin(IV)-isopropoxide-Isopropanol Solvate, Sn(OⁱPr)₄ · i-PrOH The isopropanol complex of tin(IV)-isopropoxide has been prepared by the reaction of tin tetrachloride with sodium isopropoxide. The compound forms colourless, moisture sensitive crystals, which in dry air easily release the coordinated solvent molecules. The crystal and molecular structure of Sn(OⁱPr)₄ · i-PrOH has been determinated by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2₁/c with a = 1174.2(5), b = 1428.5(3), c = 1234.1(3) pm, β = 95.37(1)° and Z = 4. The crystal structure consists of discrete, dimeric molecules in which the two tin atoms are bridged by two alkoxide groups. The octahedral coordination sphere of each tin atom is completed by one solvent molecule which, in addition, forms one hydrogen bridge to an alkoxide group of the neighboring tin atom.     

Crystal structures and thermal properties of some rare earth alkoxides with tertiary alcohols Possible precursors for atomic layer deposition of rare earth oxides

Rare earth (RE) alkoxides of Y, La, Pr, and Gd were synthesized using three tertiary alcohols namely 2,3-dimethyl-2-butanol, 2,2-dimethyl-3-ethyl-3-pentanol, and 3-isopropyl-2,4-dimethyl-pentan-3-ol. ¹H and ¹³C NMR, elemental analysis (CHN) and MS were used to characterize the complexes. New crystal structures of dimeric [Y(OCEt₂ ^t Bu)₃]₂, [La(OCEt₂ ^t Bu)₃]₂, [Gd(OC ⁱ Pr₃)₃]₂, and [La(OC ⁱ Pr₃)₃]₂ were solved. Thermal properties of these compounds were studied with TG/SDTA and vacuum sublimation experiments. With all the cations Y, La, Pr, and Gd, the compounds with smallest ligand ⁱ PrMe₂CO⁻ seem to be the most volatile. The compounds with larger alkoxo ligands have lower volatility but their thermal stability is better. Atomic layer deposition experiments showed that RE oxide thin films could be grown from these alkoxides using water as the oxygen precursor.     

Solvation Effects in Hydrolysis of 2-Methylbenzenesulfonyl Halides in Binary Solvents H2O-i-PrOH, H2O-t-BuOH, and H2O-1,4-Dioxane with Low Concentration of Organic Component

Activation parameters of hydrolysis of 2-methylbenzenesulfonyl chloride are studied, as influenced by the mole fraction of an alcohol in binary solvents H₂O-i-PrOH and H₂O-t-BuOH. The dependences of the activation parameters on the mole fraction of the second component (X ₂) are strongly nonmonotonic, like those for the previously studied hydrolysis of toluenesulfonyl chloride and bromide in aqueous dioxane. The position of the extrema along the composition axis is controlled by the hydrophobicity of nonelectrolytes. Sharp minima of H and S in the binary system H₂O-i-PrOH at X ₂ 0.03 are caused by specific solvation of the sulfonyl chloride.     

Rapid access to novel 2-alkylthiopyrimidine derivatives and attempt of their Tacrine analogs synthesis

A variety of novel 2-alkylthiopyrimidines were synthesized through simple condensation of arylidenemalononitriles with different 2-alkylthiouronium halide derivatives catalyzed by anhydrous potassium carbonate (K₂CO₃). The reactions have been carried out under mild conditions in i-PrOH, and the products were obtained in moderate to good yields with a simple work-up method. Subsequently, some examples of these compounds have been converted into Tacrine analogs by applying the Friedländer reaction.     

The effect of chloroalkane/alcohol solvent composition on the photochemical properties of copper(II) dithiocarbamate mixed-ligand complexes. EPR study

The EPR technics has been used to study the effect of solvent composition on the photochemical conversion of Cu(II) dithiocarbamate mixed-ligand complexes Cu(Et₂dtc)X (X=Cl⁻, Br⁻) and Cu(Et₂dtc)⁺…Y⁻ (Y⁻=ClO₄⁻, NO₃⁻) in chloroalkane/alcohol solutions, where chloroalkane=CCl₄, CHCl₃ or CH₂Cl₂ and alcohol=MeOH, EtOH, i-PrOH or i-BuOH. The obtained results allow to get some insight into the behaviour of the mixed-ligand complexes towards the halogen donation power of chloroalkanes and the co-ordination abilities of alcohols. The paper deals with the nature of the complexes obtained as intermediate products of photolysis.     

The dependence of the enthalpy of solution of L-methionine on the composition of water-alcohol binary solvents at 298.15 K

The integral enthalpies of solution of L-methionine in water-methanol, water-ethanol, water-n-propanol, and water-iso-propanol mixtures were measured calorimetrically at alcohol concentrations x ₂ = 0–0.4 mole fractions. The standard enthalpies of solution (Δ_sol H ^o) and transfer of L-methionine (Δ_tr H ^o) from water to a binary solvent were calculated. The influence of the structure and properties of L-methionine and the composition of aqueous-organic mixtures on its enthalpy characteristics was considered. The enthalpic pair interaction coefficients (h _xy ) between L-methionine and alcohol molecules were calculated; they were positive and increased in the series methanol (MeOH), ethanol (EtOH), n-propanol (n-PrOH), iso-propanol (i-PrOH). The enthalpy characteristics of solution and transfer of L-methionine were compared with those of glycine, L-threonine, L-alanine, and L-valine in similar binary solvents.     

Medium effect in the base hydrolysis of pentaamminebromocobalt(III) ion

Summary The effect of organic cosolvent on the rate constant of the base hydrolysis of pentaamminebromocobalt(III) ion was investigated in mixtures of H₂O with MeOH, EtOH,i-PrOH,t-BuOH, and dioxane. The thermodynamic transfer functions, corresponding to the transfer of reactants and activated complex from water to the solvent mixtures, were evaluated from kinetic measurements and from solubilities of the complex salt. The experimental results are in good agreement with a dissociative mechanismvia the conjugate base.     

Kinetics of aquation ofcis- andtrans-chloro-nitrobis-(ethylene-diamine)cobalt(III) ion in binary aqueous mixtures

Kinetics of aquation ofcis- andtrans-[Co(en)₂NO₂Cl]⁺ were investigated in aqueous mixtures of MeOH, EtOH,i-PrOH andt-BuOH at 298.1 K. The values of transfer functions corresponding to the transfer of reactant and activated complex from H₂O to the solvent mixtures were calculated from kinetic measurements and from solubilities of the complex salt. The results of the analysis of solvent effect are discussed in terms of D and I_d mechanisms. TMC 2676     

Use of isopropyl alcohol as a solvent in Ti(O-i-Pr)4-catalyzed Knöevenagel reactions

Knöevenagel reactions of aldehydes and ketones with malononitrile, isopropyl cyanoacetate and diisopropyl malonate catalyzed by Ti(O-i-Pr)₄ proceeded smoothly in i-PrOH to give the corresponding reaction products in good to high yield. 3-Substituted coumarins were prepared by the present method.     

Effect of the nature of inert solvent on the decay kinetics of the carbocation generated in the photolysis of 1,2-dihydroquinolines in methanol

The dependence of the quantum yield and the decay rate constant for the carbocation generated in the photolysis of 6-ethoxy-1,2,2,4-tetramethyl-1,2-dihydroquinoline (6-EtO-DHQ) in methanol on the solvent composition was studied in the mixtures of methanol with isopropanol, acetonitrile, and pentane by pulse photolysis. The addition of these solvents decreases the yield of the carbocation and differently affects the kinetic parameters of its decay. The carbocation decay in the mixtures MeOH-i-PrOH and MeOH-C₅H₁₂ is described by the pseudo-first order equation (k ₁), with the dependence of k ₁ having a maximum at 50 vol % of MeOH in the MeOH-i-PrOH mixtures, and k ₁ increasing with a decrease in the MeOH concentration in the MeOH-C₅H₁₂ mixtures. In the MeOH-MeCN mixtures, the value of k ₁ decreases with a decrease in the MeOH concentration, and, at the concentration of MeOH lower than 50 vol %, the contribution of the second-order reaction (k ₂) is observed. The activation energies and preexponential factors were determined in the MeOH-C₅H₁₂ mixtures of different compositions, and it was shown that E _act practically did not depend on the solvent composition and were close to E _act for other carbocations obtained in MeOH. The increase in k ₁ with a decrease in the MeOH concentration is caused by an increase in the preexponential factor. The results were discussed on the basis of the reaction mechanism involving the competing reactions of the carbocation combination with two nucleophilic particles, the MeOH molecule and the MeO⁻ anion. The composition of the mixture and the nature of the inert solvent affect strongly the course of these reactions. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 3, pp. 411–416. The article was translated by the authors.     

Reactions of hydroxyalkyl radicals with nickel(II) and copper (II) complexes of 2-methyl-5-nitro-1H-imidazole-1-ethanol: A steady-state gamma-radiolysis and flash photolysis study

The yields for the loss of chromophore of Ni(II) and Cu(II) complexes of metronidazole,G(-Ni(II)M) andG(-Cu(II)M), reached almost zero when their aqueous solutions were -irradiated in the presence, of 0.4 mol·dm^–3 of MeOH, EtOH,i-PrOH andt-BuOH in aerated medium. However, under N₂O saturated conditions, these yields attained limiting values which suggests that the hydroxyalkyl radicals, derived from the alcohols by reaction with OH, react with the complexes in deaerated medium. But in aerated medium they react preferentially with O₂. The rate constants for the reactions of the different hydroxyalkyl radicals with the complexes have been determined by the flash photolysis technique and the plausible mechanisms for the reactions have been suggested.     

Synthesis of tetrahydroisoquinoline-diamine ligands and their application in asymmetric transfer hydrogenation

The use of the tetrahydroisoquinoline scaffold is well documented in biologically active compounds. However, reports of the utilisation of tetrahydroisoquinoline compounds in asymmetric catalysis are limited. The synthesis of novel diamine ligands possessing the tetrahydroisoquinoline (tetrahydroisoquinoline) backbone and evaluation of their activity in the asymmetric transfer hydrogenation of acetophenone are presented. The diamine ligands in conjunction with i-PrOH as the hydrogen source and [RhCl₂(Cp1)]₂ as the metal precursor proved to be the most effective of the tetrahydroisoquinoline derivatives for this catalytic system. Water was found to have a profound influence on the enantioselectivity of the reaction. Optimisation of the amount water, i-PrOH and catalytic loading content rendered the best result of 70% enantioselectivity for the (S)-1-phenylethanol isomer product.     

Ion-solvent molecule interaction in nonaqueous solutions: Spin-lattice relaxation time of7Li

The spin-lattice relaxation time (T ₁) of⁷Li⁺ was measured in solutions of LiCl and LiClO₄ in protic (MeOH, EtOH,n-PrOH,i-PrOH,n-BuOH, sec-BuOH, formamide, N-methylformamide) and aprotic (MeCN, acetone, methyl ethyl ketone, propylene carbonate, dimethyl sulfoxide, dimethylformamide, hexamethylphosphotriamide) solvents and in mixtures of H₂O-formamide, H₂O–N-methylformamide, H₂O–N,N-dimethylformamide, H₂O-DMSO, H₂O-hexamethylphosphotriamide, and formamide-N,N-dimethylformamide at 25°C. The values of (1/T ₁)₀ obtained by extrapolation are discussed in terms of current theories of the magnetic relaxation of ionic nuclei. Linear correlations were found between (1/T ₁)₀ and Gutmann's donor numbers and Kosower's Z-values. These correlations indicate that relaxation of⁷Li⁺ is dominated by donor-acceptor interaction of the cation with solvent molecules. Concentration dependences of 1/T ₁ for LiCl and LiClO₄ differ from one another in a given solvent, a fact which is accounted for by a specific cation-anion short-range potential. The quantity 1/T ₁ of⁷Li⁺ atC=1 mole per 55.5 moles of mixed solvent as a function of solvent composition show characteristic features, which are discussed in terms of the relaxation mechanism proposed.     

Kinetics of aquation of cis-aquabromo-bis(ethylenediamine) complexes of cobalt(III) and chromium(III) in binary aqueous mixtures

Summary The kinetics of aquation of cis-[Co(en)₂(H₂O)Br]²⁺ and cis-[Cr(en)₂(H₂O)Br]²⁺ (en = ethylenediamine) were investigated in aqueous mixtures of MeOH, EtOH, i-PrOH and t-BuOH. The values of transfer functions corresponding to the transfer of reactants and activated complex from water to the solvent mixtures were evaluated from kinetic measurements and from solubilities of the complex salt. Analysis of the solvent effect confirmed a common I_d mechanism for the aquation of the Co^III and Cr^III complexes.