Monomer-isomerization polymerization. V. Effects of transition metal compounds on monomer-isomerization polymerizations of butene-2 and pentene-2

In order to clarify the correlation between polymerization and monomer isomerization in the monomer-isomerization polymerization of β-olefins, the effects of some transition metal compounds which have been known to catalyze olefin isomerizations on the polymerizations of butene-2 and pentene-2 with Al(C₂H₅)₃–TiCl₃ or Al(C₂H₅)₃–VCl₃ catalyst have been investigated. It was found that some transition metal compounds such as acetylacetonates of Fe(III), Co(II), and Cr(III) or nickel dimethylglyoxime remarkably accelerate these polymerizations with Al(C₂H₅)₃–TiCl₃ catalyst at 80°C. All the polymers from butene-2 were high molecular weight polybutene-1. With Al(C₂H₅)₃–VCl₃ catalyst, which polymerizes α-olefins but does not catalyze polymerization of β-olefins, no monomer-isomerization polymerizations of butene-2 and pentene-2 were observed. When Fe(III) acetylacetonate was added to this catalyst system, however, polymerization occurred. These results strongly indicate that two independent active centers for the olefin isomerization and the polymerizations of α-olefins were necessary for the monomer-isomerization polymerizations of β-olefins.     

Catalytic action of metallic salts in autoxidation and polymerization. VIII. Polymerization of methyl methacrylate by various metal acetylacetonate–cyclic ether hydroperoxides

Polymerization of methyl methacrylate by cyclic ether hydroperoxide–metal acetylacetonate systems for a number of different metals was carried out to compare with the tert-butyl hydroperoxide–metal acetylacetonate initiating systems. The rate of polymerization of methyl methacrylate with cyclic ether hydroperoxides as initiating systems was much higher than that with tert-butyl hydroperoxide. In cyclic ether hydroperoxide initiating systems, V(III), Co(II,III), Fe(III), Cu(II), and Mn(II) promoted the polymerization rate markedly, and Zn(II), Ni(II), Al(III), and Mg(II) had little or no effect; in the tert-butyl hydroperoxide initiating system only V(III), Co(II), and Mn(II) enhanced polymerization rate, and most of other metals showed little or no effect. Furthermore, noticeable differences in color of solution and appearance during polymerization, and in relation between conversion and the degree of polymerization were observed. The effect of metal acetylacetonates on hydroperoxide initiators in polymerization of methyl methacrylate was also compared with that on the decomposition of hydroperoxides.     

Studies of adsorption and solution of acetylacetonates of Cr(III), Co(III) and Al(III) by gas chromatography

Summary Specific retention volumes, adsorption isotherms, molar heats of solution and changes of the entropy were determined from chromatographic data, which was obtained by the gas chromatographic separation of metal acetylacetonates. The retention data for Cr(III), Co(III) and Al(III) acetylacetonates were measured at different temperatures and different flow rates. From the retention data other values associated with adsorption and solution phenomena were calculated.     

Electronic Structure and Magnetic Properties of a High-Spin MnIII Complex: [Mn(mesacac)3] (mesacac=1,3-Bis(2,4,6-trimethylphenyl)-propane-1,3-dionato)

Metal acetylacetonates of the general formula [M(acac)₃] (M^III=Cr, Mn, Fe, Co) are among the best investigated coordination compounds. Many of these first-row transition metal complexes are known to have unique electronic properties. Independently, photophysical research with different β-diketonate ligands pointed towards the possibility of a special effect of the 2,4,6-trimethylphenyl substituted acetylacetonate (mesacac) on the electron distribution between ligand and metal (MLCT). We therefore synthesized and fully characterized the previously unknown octahedral title complex. Its solid-state structure shows a Jahn-Teller elongation with two Mn−O bonds of 2.12/2.15 Å and four Mn−O bonds of 1.93 Å. Thermogravimetric data show a thermal stability up to 270 °C. High-resolution mass spectroscopy helped to identify the decomposition pathways. The electronic state and spin configuration of manganese were characterized with a focus on its magnetic properties by measurement of the magnetic susceptibility and triple-zeta density functional theory (DFT) calculations. The high-spin state of manganese was confirmed by the determination of an effective magnetic moment of 4.85 μ_B for the manganese center.     

Effect of Cr(III), Fe(III), Co(III), and Ni(II) acetylacetonates on the formation and thermal oxidative degradation of epoxy-anhydride polymers and composites

The effect of Cr(III), Fe(III), Co(III), and Ni(II) acetylacetonates on epoxy-anhydride polycondensation in preparation of unmodified polymeric materials based on UP-650T epoxy resin and isomethyltetrahydrophthalic anhydride and of epoxy-siloxane hybrid composites was examined The resistance of the materials obtained to high-temperature oxidation and thermal oxidative degradation was evaluated.     

Thermal study of chelates of Co(II), Cu(II), Ni(II), Cr(III), Mo(III), and Fe(III) with bis(acetylacetone)ethylenediimine on activated silica gel surface

The divalent copper, nickel, cobalt and trivalent chromium, molybdenium and iron chelate compounds derived from bis(acetylacetone) ethylenediimine were grafted on activated silica gel using a batch process in methanolic solution. The sequence of the maximum retention capacity was Cr(III)>Mo(III)>Fe(III)>Co(II)>Ni(II)>Cu(II). Calorimetric titration was employed to study the interaction of activated silica gel with these series of metal chelate compounds. Exothermic enthalpic results were obtained throughout all interactions process. The spontaneity of these systems was reflected in negative and positive free Gibbs energy from entropic values.     

Facile synthesis and reactions of some olefin-substituted acetylacetonate complexes

Synthesis of transition metal complexes of olefin-substituted acetylacetones has been effected by reaction of nonaqueous solutions of substituted acetylacetones with the metal salt in the presence of Zn or Mg. 3-Allylacetylacetonates of Be(II), Cu(II), Ni(II), Fe(III), Co(II), Pd(II) and Zn(II) have thus been synthesized in quantitative yields. 3-Propylideneacetylacetone, which exists mainly in the keto form, afforded the corresponding 3-propenylacetylacetonates in which 3-propylideneacetylacetone has rearranged to 3-propenylacetylacetone which has a greater probability of existing in the enol form, thus making its reaction with metal ions favorable. Metal–metal exchange reactions of transition metal salts with olefin-substituted Zn or Mg acetylacetonates provide yet another route for the synthesis of transition metal olefin-substituted acetylacetonates. The homogeneous catalytic hydrogenation of the olefin moiety in olefin-substituted metal acetylacetonates could be achieved by a Pt/Sn catalyst.     

Thermal and spectral studies on complexes derived from tetradentate Schiff bases

Several new complexes of Schiff bases ligands H₄La and H₄Lb with transition metal ions such as Cr(III), Fe(III), Co(II) and Zn(II) are synthesized. Elemental analysis, infrared, UV–Vis and thermal analysis, as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. A square planar geometry is suggested for Zn(II) complexes, while an octahedral geometry suggested for the Cr(III), Fe(III) and Co(II) complexes. The thermal decomposition of complexes was found to be first order reaction and the thermodynamic parameters corresponding to the different decomposition steps were reported.     

Solid Phase Sorption of Phenols on Metals Acetylacetonates

The solid phase extraction properties of surface layers of Eu(III), Al(III), Fe(III), Cr(III) acetylacetonates are compared for sorption some phenols and chlorophenols. The effects of the energies of adsorption and complexation on the retention of various sorbates were calculated. GC methods with preconcentration are proposed to evaluate phenols by means of solid-phase extraction on a sorbent with a surface layer of Eu acetylacetonate with extraction effectiveness of 85%.     

Fractional sublimation of some metal chelates of thenoyltrifluoroacetone

Studies on the fractional sublimation of various metal β-diketone chelates have been extended to include the chelates of thenoyltrifluoroacetone (TTA). Many of the common metal chelates were found to be stable, to sublime readily, and to form well-defined zones in the vacuum fractional sublimator. Of the 17 chelates reported only those of manganese (II) and iron(II) were not volatile. The chelates of UO₂(II), Zr(IV), Pb(II), and Cr(III) partially decomposed during sublimation and their recovery was incomplete. The recovery of the sublimed chelates of Ni(II), Mg(II), Al(III), Pd(II), Co(II), Cu(II). Fe(III), Tl(III), Zn(II) and Be(II) ranged from 87 to 100%, with most recoveries being quantitative. The sublimation recrystallization zone temperatures of the various chelates are compared to those of the metal acetylacetonates and the benzoyltrifluoroacetonates; in general, the metal chelates of TTA sublime more readily than those of benzoyltrifluoroacetone but are potentially less useful for fractional sublimation separations than the corresponding metal acetylacetonates. Even so, a quantitative separation of iron(III) from Ni(II), Al(III), Mn(II), and Fe(II) is proposed that depends upon the fractional sublimation of the TTA chelates.     

Toward a general strategy for the synthesis of heterobimetallic coordination complexes for use as precursors to metal oxide materials: synthesis, characterization, and thermal decomposition of Bi(2)(Hsal)(6).M(acac)(3) (M = Al, Co, V, Fe, Cr)

Bismuth(III) salicylate, [Bi(Hsal)(3)](n), reacts readily with the trivalent metal beta-diketonate compounds M(acac)(3) (acac = acetylacetonate; M = Al, V, Cr, Fe, Co) to produce trinuclear coordination complexes of the general formula Bi(2)(Hsal)(6).M(acac)(3) (M = Al, V, Cr, Fe, Co) in 60-90% yields. Spectroscopic and single crystal X-ray diffraction experiments indicate that these complexes possess an unusual asymmetric nested structure in both solution and solid state. Upon standing in dichloromethane solution, Bi(2)(Hsal)(6).Co(acac)(3) eliminates Bi(Hsal)(3) to give the 1:1 adduct Bi(Hsal)(3).Co(acac)(3). The 2:1 heterobimetallic molecular compounds undergo facile thermal decomposition on heating in air to 475 degrees C to produce heterometallic oxide materials, which upon annealing for 2 h at 700 degrees C form crystalline oxide materials. The synthetic approach detailed here represents a unique, general approach to the formation of heterobimetallic bismuth-based coordination complexes via the coordination of M(acac)(3) complexes to bismuth(III) salicylate.     

The microdetection of organoparticulates from diazonium compounds

The thermal decompositions of a series of diazonium compounds have been investigated using the new technique of organic particulate analyses (OPA). This extremely sensitive technique makes possible the detection of particulates emitted from the diazonium compounds during thermal decomposition. The submicron particulates derived in this fashion are readily detectable by their influence on the output current of an ion chamber detector or by their effect on the cloud chamber of a condensation nuclei monitor.Of the 14 diazonium compounds evaluated, 11 were found to exhibit particulation behavior below 190 °C. In some cases, very strong particulation was detectable. No apparent correlation between the organic particulation temperature range (OPTR) and their literature thermal decomposition temperatures was evident. Efforts were made to characterize the nature of the particulates using mass spectrometry but this was hampered by the extreme complexities of the spectral patterns.In terms of their abilities to produce particulates, the diazonium compounds can be placed in four main groups reflecting their chemical composition, molecular size, and degree of substitution. Vapor phase association of the molecular fragments formed during thermal decomposition might be occurring to produce the required particulate size detectable by the present instrumentation.     

On the mechanism of electroreduction of sulphur-containing ligands induced by the electroreduction of transition metal cations

The large scale electrolysis of Zn(II), Cd(II), Hg(II), Cu(II), Ni(II), Co(II), Co(III), Fe(II), Mn(II), Cr(II), Cr(III), Bi(III), In(III) and Sb(III) at mercury electrodes in presence of mercaptoacetic acid, 3-mercaptopropionic acid, cysteine and thiourea was carried out and the products were investigated. In case of transition metal ions the catalytic reduction of organic compounds resulting in the formation of sulphide ions was found. There are two possible ways of the production of these ions: (i) consisting in the formation of a complex between transition metal ion and organic ligand which is subsequently, reduced, and (ii) direct electroreduction of organic compound on the electrode modifiied by the deposition of metal and metal sulphide. For both cases the mechanism of electroreduction was discussed.     

Silica Gel Modified Due to Pyrolysis of Acetylacetone and Metal (Ti, Cr, Co, Ni, Zn, Zr) Acetylacetonates

Mesoporous silica gels modified due to pyrolysis of acetylacetone or acetylacetonates (AcAc) of zirconium [Zr(AcAc)(4)], titanium [titanyl TiO(AcAc)(2)], nickel [Ni(AcAc)(2)], zinc [Zn(AcAc)(2)], chromium [Cr(AcAc)(3)], and cobalt [Co(AcAc)(2)] were studied using nitrogen adsorption-desorption, TPD-DTG, TEM, XRD, and XRF methods. Grafted C/X phases consist of metal compounds (X denotes oxide, silicate, or metal crystallites) and pregraphite pyrocarbon, whose characteristics can be varied by changing the metal in M(AcAc)(n). The structural parameters of C/X/SiO(2), such as the specific surface area of micro- and mesopores, pore volume, pore size and fractal dimension distributions, and adsorptive ability, depend nonlinearly on the concentrations of the C/X deposit due to alterations in the topology of grafted matters with increased concentrations and a possible catalytic effect of the X phase on pyrolysis. Copyright 2000 Academic Press.     

Solubility of β-diketonate complexes for cobalt(III) and chromium(III) in supercritical carbon dioxide

The solubilities of tris(2,2,6,6-tetramethyl-3,5-heptanedionate) cobalt(III) (Co(thd)₃) and chromium(III) (Cr(thd)₃) in supercritical carbon dioxide (scCO₂) were measured at temperatures ranging from 313 to 343 K. The measurements were carried out using a circulation-type apparatus with a UV–vis spectrometer. The solubilities of both Co(thd)₃ and Cr(thd)₃ increased as both the density of scCO₂ and the temperature increased, which has the same tendency as cobalt(III) acetylacetonate (Co(acac)₃) and chromium(III) acetylacetonate (Cr(acac)₃) had in our previous work. The solubilities of Cr(thd)₃ were higher than that of Co(thd)₃, and the solubilities of Co(thd)₃ and Cr(thd)₃ were about 50- and 70-fold higher than those of Co(acac)₃ and Cr(acac)₃, respectively. The measured solubilities of the metal complexes were correlated with the equation based on Chrastil's equation. The parameters were determined by correlating the experimental data for each metal complex, and the correlated results well reproduced the experimental data, especially Co(thd)₃. Moreover, the charge density distributions on the molecular surface of CO₂ and the metal complexes used in the measurement were estimated by the quantum chemical calculation and the COSMO-RS to clear the effect of the molecular structure of the metal complexes on the affinity for CO₂.     

Ligand exchange reactions between Cu(II), Pb(II), Al(III), and Cr(III) acetylacetonates and dipivaloylmethanates: The possibility of using exchange reactions in estimation of standard enthalpies of formation of metal β-diketonates

Ligand exchange reactions between Cu(II), Pb(II), Al(III), and Cr(III) acetylacetonates and dipivaloylmethanates were studied by mass spectrometry with sample evaporation from an analog of the Knudsen effusion cell (direct inlet probe). It was shown that exchange reactions can be used to estimate the standard enthalpies of formation of metal β-diketonates.     

乙酰丙酮在低温电热蒸发ICP-AES中的化学改进作用机理研究

近年来 ,低温蒸发技术的研究和应用引起了人们的重视 [1～ 3 ] .我们 [4]曾报道应用乙酰丙酮试剂作化学改进剂 ,于石墨管中低温 (～ 75 0℃ )蒸发铍的乙酰丙酮螯合物的 ETV-ICP-AES法 ,并用于人发中痕量铍的测定 .本文从机理上探讨了待测物 (铍或铬 )在石墨管中的蒸发及传输形式 ;研究了相应的乙酰丙酮螯合物的生成条件及主要影响因素 ;在此基础上得出在低温蒸发条件下相应的规律 .1　实验部分1.1　仪器装置　所用的 ICP-AES仪器、电热蒸发装置及它们之间的连接与文献 [1,4]相同 .紫外 -可见分光光度计 (日本岛津 UV-2 0 0 0 ) ,仪器…     

Organic particulate analysis of isocyanate compounds

The technique of Organic Particulate Analysis (OPA) has been employed to investigate the thermal decomposition of a series of isocyanate compounds; OPA measures the temperature at which particulate or aerosol matter is emitted from a heated organic substance. Of the eighteen isocyanate compounds investigated, seventeen showed strong organoparticulation activity below 200 °C. With the possible exception of four isocyanates, no obvious correlation exists between the OPA values and the melting or decomposition point of the compound.In an attempt to characterize the nature of the particulate matter derived from these compounds, mass-spectral data were obtained at thermoparticulation. Most of the massspectral particulate analyses showed the presence of very polar species (such as diethylamine) which were capable of exhibiting hydrogen-bonding properties. This hydrogen bonding gives rise to particulate matter of sufficient size to be detected by an ion chamber instrument. The ability of phenols to particulate, whereas thiophenols do not particulate, is discussed.     

Calorimetric and Thermal Investigation of Metal Derivatives of 6-aminopicolinic Acid

The comparison of thermal and calorimetric properties of metal derivatives of 6-aminopicolinic acid (APH) is presented. The salts and complexes of APH with Cr(III), Cd(II), Cu(II), Ni(II), Pb(II), Co(II)and Ag(I) have been studied by TG-DTA and DSC methods up to 1200°C in a nitrogen atmosphere. Decomposition processes are proposed. The decarboxylation, deamination and carbonation of the organic fragments of molecules take place. The compounds decompose to metal or to metal oxides. The values of the transition enthalpy were determinated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Some new initiators and inhibitors in vinyl polymerization

This work examines some discrepancies between claimed effects in polymerization of certain metal acetylacetonates. Cupric acetylacetonate inhibits the thermal polymerization of styrene but acts only as a retarder in the sensitized polymerization of styrene and in the thermal polymerization of methyl methacrylate. Aluminium acetylacetonate initiates weakly the polymerization of styrene, but ferric acetylacetonate does not influence the rates of polymerization of the above mentioned monomers.