Novel enhancement effect of a proton donor on chelate extraction: Extraction of iron(III) with acetylacetone and 3,5-dichlorophenol

Effect of 3,5-dichlorophenol (DCP) on the extraction of Fe(III) with acetylacetone (Hacac) in nonpolar organic solvents has been studied. It is found that a mixture of Hacac and DCP in heptane gives much higher extraction of Fe(III) than Hacac alone. Such novel enhancement effect is ascribable to the association of tris(acetylacetonato)iron(III) [Fe(acac)₃] with DCP in the organic phase by hydrogen bonding. Association of Hacac with DCP has also been investigated and the intrinsic extraction equilibrium of Fe(III) is analyzed by using the equilibrium concentration of free Hacac and DCP. The association complexes are found to be Fe(acac)₃ · n DCP (n=1, 2, 3) in heptane, and the overall association constants (_{ass, n}) are determined to be log _{ass, 1} = 3.41, log _{ass, 2}, = 5.97 and log _{ass, 3}, = 7.50.     

Covalent binding of fullerene C<Subscript>60</Subscript> to pharmacologically important compounds

The cycloaddition of diazo compounds derived from α-tocopherol, betulinic acid, ursolic acid, and Trolox methyl esters to fullerene C₆₀ in the presence of a Pd(acac)₂-PPh₃-Et₃Al catalytic system was performed. The reactions of the diazo compounds derived from the above-mentioned pharmacologically important compounds with fullerene C₆₀ in the presence of the Pd(acac)₂-PPh₃-Et₃Al system (1: 2: 4) afford predominantly the previously inaccessible pyrazolinofullerenes. A change in the component ratio of the Pd(acac)₂-PPh₃-Et₃Al catalyst from 1: 2: 4 to 1: 4: 4 favors the formation of methanofullerenes exclusively.     

Interaction of 2,2,6,6-tetramethylpiperidine-1-oxyl chloritewith alcohols

The kinetics of the oxidation of a series of alcohols (viz., ethanol, propan-2-ol, butan-1-ol, butan-2-ol, heptan-4-ol, decan-2-ol, propan-1,3-diol, butan-2,3-diol, cyclohexanol, benzyl alcohol, and borneol) with the oxoammonium salt 2,2,6,6-tetramethylpiperidine-1-oxyl chlorite in acetonitrile was studied by spectrophotometry. The products of oxidation of primary alcohols are the corresponding aldehydes and carboxylic acids, and the products of oxidation of secondary alcohols are ketones. The reaction rate is described by the second order equation. The rate constants and activation parameters were determined. The rate constant as a function of the alcohol nature is described by the one-parameter Taft equation.     

A Zeolite‐Supported Molecular Ruthenium Complex with η6‐C6H6 Ligands: Chemistry Elucidated by Using Spectroscopy and Density Functional Theory

An essentially molecular ruthenium–benzene complex anchored at the aluminum sites of dealuminated zeolite Y was formed by treating a zeolite‐supported mononuclear ruthenium complex, [Ru(acac)(η²‐C₂H₄)₂]⁺ (acac=acetylacetonate, C₅H₇O₂^?), with ¹³C₆H₆ at 413 K. IR, ¹³C NMR, and extended X‐ray absorption fine structure (EXAFS) spectra of the sample reveal the replacement of two ethene ligands and one acac ligand in the original complex with one ¹³C₆H₆ ligand and the formation of adsorbed protonated acac (Hacac). The EXAFS results indicate that the supported [Ru(η⁶‐C₆H₆)]²⁺ incorporates an oxygen atom of the support to balance the charge, being bonded to the zeolite through three Ru? O bonds. The supported ruthenium–benzene complex is analogous to complexes with polyoxometalate ligands, consistent with the high structural uniformity of the zeolite‐supported species, which led to good agreement between the spectra and calculations at the density functional theory level. The calculations show that the interaction of the zeolite with the Hacac formed on treatment of the original complex with ¹³C₆H₆ drives the reaction to form the ruthenium–benzene complex.     

Structure characterisation of the organoaluminium intermediate resulting from the alkylation of a chelated carbonyl group. Molecular structure of the trinuclear [MeAl][C12H20O4][AlMe2]2 compound

The interaction of Me₃Al with Me₂Al(acac) results in the carbonyl alkylation of the chelating acetylacetonate ligand and formation of trinuclear complex [MeAl][C₁₂H₂₀O₄][AlMe₂]₂ (1). The title compound has been characterised by ¹H-and ²⁷Al-NMR spectroscopy. The ¹H-NMR spectra are consistent with the presence of two distinct isomers in an equimolar ratio: cis-1 and trans-1. Both isomers contain two methylated acac units bridged by three organoaluminium moieties: central five-coordinated methyl aluminium species and two terminal four-coordinated dimethylaluminium species. The structure of cis-1 has been confirmed by X-ray crystallography which revealed that the five-coordinated aluminium atom rises in almost ideal square pyramidal geometry. The role of the molar ratio of reactants is discussed.     

The Structure of Mn(acac)3—Experimental Evidence of a Static Jahn–Teller Effect in the Gas Phase

The structure of free manganese(III) tris(acetylacetonate) [Mn(acac)₃] was determined by mass‐spectrometrically controlled gas‐phase electron diffraction. The vapor of Mn(acac)₃ at 125(5) °C is composed of a single conformer of Mn(acac)₃ in C₂ symmetry with the central structural motif of a tetragonal elongated MnO₆ octahedron and 47(2) mol % of acetylacetone (Hacac) formed by partial thermal decomposition of Mn(acac)₃. Three types of Mn−O separations have been refined (r_h1=2.157(16), 1.946(5), and 1.932(5) Å. We have found no indication for a significant deviation of the ‐C−C−C−O−Mn−O‐ six‐membered rings from planarity, which is observed in the solid state.     

Monomer-isomerization polymerization. XXIII.. Monomer-isomerization polymerization of 5-phenyl-2-pentene with ziegler–natta catalysts

5-Phenyl-2-pentene (5Ph2P) was found to undergo monomer-isomerization polymerization with TiCl₃–R₃Al (R = C₂H₅ or i-C₄H₉, Al/Ti > 2) catalysts to give a polymer consisting of exclusively 5-phenyl-1-pentene (5Ph1P) unit. The geometric and positional isomerizations of 5Ph2P to its terminal and other internal isomers were observed to occur during polymerization. The catalyst activity of alkylaluminum examined to TiCl₃ was in the following order: (C₂H₅)₃Al > (i-C₄H₉)₃Al > (C₂H₅)₂AlCl. The rate of monomer-isomerization polymerization of 5Ph2P with TiCl₃–(C₂H₅)₃Al catalyst was influenced by both the Al/Ti molar ratio and the addition of nickel acetylacetonate [Ni(acac)₂], and the maximum rate was observed at Al/Ti = 2.0 and Ni/Ti = 0.4 in molar ratios.     

Monomer-Isomerization polymerization. XXVIII. Catalytic activity of transition metals and alkylaluminums in monomer-isomerization polymerization of 2-butene

Monomer-isomerization polymerization of cis-2-butene (c2B) with Ziegler–Natta catalysts was studied to find a highly active catalyst. Among the transition metals [TiCl₃, TiCl₄, VCl₃, VOCl₃, and V (acac)₃] and alkylauminums used, TiCl₃? R₃Al (R = C₂H₅ and i-C₄H₉) was found to show a high-activity for monomer-isomerization polymerization of c2B. The polymer yield was low with TiCl₄? (C₂H₅)₃Al catalyst. However, when NiCl₂ was added to this catalyst, the polymer yield increased. With TiCl₃? (C₂H₅)₃Al catalyst, the effect of the Al/Ti molar ratio was observed and a maximum for the polymer yields was obtained at molar ratios of 2.0–3.0, but the isomerization increased as a function of Al/Ti molar ratio. The valence state of titanium on active sites for isomerization and polymerization is discussed.     

Monomer-isomerization polymerization. XXVI. Formation of polyallylcyclohexane from propenylcyclohexane through monomer-isomerization polymerization with Ziegler–Natta catalysts

Monomer-isomerization polymerization of propenycyclohexane (PCH) with TiCl₃ and R_3-xAICI_x (R = C₂H₅ or i-C₄H₉, x = 1–3) catalysts was studied. It was found that PCH underwent monomer-isomerization polymerization to give a high molecular weight polymer consisting of an allylcyclohexane (ACH) repeat unit. Among the alkyaluminum cocatalysts examined, (C₂H₅)₃Al was the most effective cocatalyst for the monomer-isomerization polymerization of PCH, and a maximum for the polymerization was observed at a molar ratio of Al/Ti of about 2.0. The addition of isomerization catalysts such as nickel acetylacetonate [Ni(acac)₂] to the TiCl₃–(C₂H₅)₃Al catalyst accelerated the monomer-isomerization polymerization of PCH and gave a maximum for the polymerization at a Ni/Ti molar ratio of 0.5. PCH also undergoes monomer-isomerization copolymerization with 2-butene (2B).     

Polymerization of styrene to isotactic polymer with MAO-Ni(acac)2. Examination of the factors that influence activity and stereospecificity

The soluble catalyst system methylaluminoxane (MAO)-Ni(acac), (acac: acetylacetonate) gives polystyrene consisting of an amorphous (aPS) and a crystalline isotactic (ips) fraction. Al(CH₃)₃, which is always present in commercial samples of MAO, decreases both polymer yield and stereospecificity. The polymer yield increases with increasing the MAO/Ni ratio but, at the same time, the iPS/aPS ratio decreases. Addition of N(C₂H₅)₃ (mole ratio N/Ni = 1) increases the proportion of the isotactic fraction, while it decreases the polymer yield. A tentative interpretation of the stereospecificity is reported.     

Hydrosilylation of 1,3-dienes with methyldichlorosilane in the presence of Ni catalyst systems

Conclusions The Ni(acac)₂-Et₃Al and Ni(acac)₂-i-Bu₃Al systems effectively catalyze with 1,4-addition of methyldichlorosilane to 1,3-dienes at 20–25C. In the case of butadiene and isoprene, the reaction is accompanied by the formation of appreciable amounts of bis-silylated products, viz., 1,4-bis(methyldichlorosilyl)-cis-2-butene and 1,4-bis(methyldichlorosilyl)-3-methyl-2-butene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 418–421, February, 1979.     

Role of the Support in Catalysis: Activation of a Mononuclear Ruthenium Complex for Ethene Dimerization by Chemisorption on Dealuminated Zeolite Y

A set of supported ruthenium complexes with systematically varied ratios of chemisorbed to physisorbed species was formed by contacting cis‐[Ru(acac)₂(C₂H₄)₂] ( I ; acac=C₅H₇O₂^?) with dealuminated zeolite Y. Extended X‐ray absorption fine structure (EXAFS) spectra used to characterize the samples confirmed the systematic variation in the loadings of the two supported species and demonstrated that removal of bidentate acac ligands from I accompanied chemisorption to form [Ru(acac)(C₂H₄)₂]⁺ attached through two Ru? O bonds to the Al sites of the zeolite. A high degree of uniformity in the chemisorbed species was demonstrated by sharp bands in the infrared (IR) spectrum characteristic of ruthenium dicarbonyls that formed when CO reacted with the anchored complex. When the ruthenium loading exceeded 1.0 wt % (Ru/Al≈1:6), the additional adsorbed species were simply physisorbed. Ethene ligands on the chemisorbed species reacted to form butenes when the temperature was raised to approximately 393 K; acac ligands remained bonded to Ru. In contrast, ethene ligands on the physisorbed complex simply desorbed under the same conditions. The chemisorption activated the ruthenium complex and facilitated dimerization of the ethene, which occurred catalytically. IR and EXAFS spectra of the supported samples indicate that 1) Ru centers in the chemisorbed species are more electron deficient than those in the physisorbed species and 2) Ru–ethene bonds in the chemisorbed species are less symmetric than those in the physisorbed species, which implies the presence of a preferred configuration for the catalytic dimerization.     

Color tunable phosphorescent light-emitting diodes based on iridium complexes with substituted 2-phenylbenzothiozoles as the cyclometalated ligands

Several iridium complexes {iridium(III)bis[2-(3-methoxyphenyl)-1,3-benzothiozolato-N,C^2′] acetylacetonate (MeO-BT)₂Ir(acac), iridium(III)bis[2-(2,4-difluorophenyl)-1,3-benzothiozolato-N,C^2′] acetylacetonate (2F-BT)₂Ir(acac), and iridium(III)bis[2-(2,4-difluorophenyl)-6-fluoro-1,3-benzothiozolato-N,C^2′] acetylacetonate (3F-BT)₂Ir(acac)} having different substituents on 2-phenylbenzothiazole have been synthesized. The phosphorescent light emitting diodes (PHOLEDs) using these iridium complexes as dopant emitters were fabricated. The experimental results revealed that the emissive colors of PHOLEDs could be finely tuned by suitable modification of the substituents on the 2-phenylbenzothiazole ligands. Furthermore, these iridium complexes show better emissive properties than the known iridium(III)bis(2-phenylbenzothiozolato-N,C^2′) acetylacetonate (BT)₂Ir(acac).     

High polymerization of methyl methacrylate with organonickel/MMAO systems

A series of nickel complexes, including Ni(acac)₂, (C₅H₅)Ni(η³‐allyl), and [NiMe₄Li₂(THF)₂]₂, that were activated with modified methylaluminoxane (MMAO) exhibited high catalytic activity for the polymerization of methyl methacrylate (MMA) but showed no catalytic activity for the polymerization of ethylene and 1‐olefins. The resulting polymers exhibited rather broad molecular weight distributions and low syndiotacticities. In contrast to these initiators, the metallocene complexes (C₅H₅)₂Ni, (C₅Me₅)₂Ni, (Ind)₂Ni, and (Me₃SiC₅H₄)₂Ni provided narrower molecular weight distributions at 60 °C when these initiator were activated with MMAO. Half‐metallocene complexes such as (C₅H₅)NiCl(PPh₃), (C₅Me₅)NiCl(PPh₃), and (Ind)NiCl(PPh₃) produced poly(methyl methacrylate) (PMMA) with much narrower molecular weight distributions when the polymerization was carried out at 0 °C. Ni[1,3‐(CF₃)₂‐acac]₂ generated PMMA with high syndiotacticity. The NiR(acac)(PPh₃) complexes (R = Me or Et) revealed high selectivity in the polymerization of isoprene that produced 1,2‐/3,4‐polymer at 0 °C exclusively, whereas the polymerization at 60 °C resulted in the formation of cis‐1,4‐rich polymers. The polymerization of ethylene with Ni(1,3‐tBu₂‐acac)₂ and Ni[1,3‐(CF₃)₂‐acac]₂ generated oligo‐ethylene with moderate catalytic activity, whereas the reaction of ethylene with Ni(acac)₂/MMAO produced high molecular weight polyethylene. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4764–4775, 2000     

Structural characterization of a hybrid terpyridine–pyrazine ligand and its one‐dimensional ZnII coordination polymer: a computational approach to conventional and nonconventional intermolecular interactions

The structures of a new hybrid terpyridine–pyrazine ligand, namely 4′‐[4‐(pyrazin‐2‐yl)phenyl]‐4,2′:6′,4′′‐terpyridine (L2), C₂₅H₁₇N₅, and its one‐dimensional coordination polymer catena‐poly[[bis(acetylacetonato‐κ²O,O′)zinc]‐μ‐4′‐[4‐(pyrazin‐2‐yl‐κN⁴)phenyl]‐4,2′:6′,4′′‐terpyridine‐κN¹], [Zn(C₅H₇O₂)₂(C₂₅H₁₇N₅)]_n or [Zn(acac)₂(L2)]_n (Hacac is acetylacetone), are reported. Packing interactions in both crystal structures are analyzed using Hirshfeld surface and enrichment ratio techniques. For the simpler structure of the monomeric ligand, further studies on the interaction hierarchy using the energy framework approach were made. The result was a complete picture of the intermolecular interaction landscape, which revealed some subtle details, for example, that some weak (at first sight negligible) C—H…N interactions in the structure of free L2 play a relevant role in the crystal stabilization.     

Sol-Gel Preparation of Highly Active Sulfated Zirconia Supported by Alumina Catalysts

A series of sulfated mixed oxides of alumina and zirconia having a relative composition of 5% and 10% of ZrO₂ was prepared by means of sol-gel methods using zirconium propoxide or zirconium acetylacetone as precursor. The characterization of the physicochemical properties was carried out using ²⁷Al NMR, XRD, N₂ adsorption at 77 K, thermogravimetry, FTIR analysis of adsorbed pyridine, ²⁷Al NMR-MAS and XPS. The catalytic properties were studied by means of isomerization of n-hexane at 250°C. Results obtained allowed to propose that the use of Zr(acac)₄ as a zirconium precursor leads to a better retention of sulfate species which seems to form polymeric superficial sites. The symmetry of aluminium undergo an increase from tetrahedral to octahedral coordination and Zirconium atoms seems to be located in the second coordination sphere of Al. XRD analysis indicated an amorphous structure of obtained solids calcined at 650°C. The sulfated solids presented both Lewis and Brönsted acidic sites. Catalytic results showed that both activity and selectivity towards isomerization products were better using Zr (acac)₄ as precursor. Furthermore, the increase of the Zr loading affected considerably the catalytic properties of sulfated zirconia supported by alumina.     

Chemical behavior of positive mouns in diamagnetic metal acetylacetonate solid solutions

Diamagnetic muon yields (P _D) in (Al _x Co_1−x )(acac)₃ and (Ga _x Co_1−x )(acac)₃ systems were investigated. Both in (Al _x Co_1−x )(acac)₃ and (Ga _x Co_1−x )(acac)₃, Co(acac)₃ was more influential on diamagnetic muon yield than Al(acac)₃ and Ga(acac)₃. Zerofield muon spin relaxation rate suggests that the diamagnetic muon resides in the vicinity of Co(acac)₃ molecules.     

Catalytic cycloaddition of diazoalkanes with heterocyclic substituents to fullerene C<Subscript>60</Subscript>

Methanofullerenes were directly synthesized under mild conditions by cycloaddition to fullerene C₆₀ of diazoalkanes generated in situ by oxidation of ketone hydrazones containing a heterocyclic fragment with manganese(IV) oxide in the presence of the catalytic system Pd(acac)₂-2 PPh₃-4 Et₃Al.     

Thermochemical properties of some f-electron element β-diketonates,and metal-oxygen bond energies. lanthanum(III)β-diketonates

The standard molar enthalpies of formation of the crystalline lanthanum(III) chelate complexes with pentane-2,4-dione (acetylacetone, Hacac) and 1-phenylbutane-1,3-dione (benzoylacetone, Hbzac) were determined by the solution calorimetry method. The following values ofΔH _f(s) ⁰ (kJ mol^?1) were obtained: La(acac)_3', ?1916.2±7.0; La(bzac)₃ · 2H₂O, ?2099.1 ±9.7. The enthalpies of the hypothetical complex dissociation reactions in the gaseous phase: $$LaL_{3(g)} = La_{(g)} + 3L_{(g)} and LaL_{3(g)} = La_{(g)}^{ + 3} + 3L_{(g)}^ - $$ were calculated as a measure of the mean bond dissociation energy, (La-O), and the mean coordinate bond dissociation energy, CB>(La-O), respectively.     

Nicke(II) complexes of half unit,symmetric and unsymmetric Schiff base ligands

Summary The template reaction of isonitrosoacetylacetone (Hina) witho-phenylenediamine (o-phenen) in the presence of (MeCO₂)₂Ni·4H₂O in EtOH yielded three types of nickel(II) complexes (depending on the molar ratio of the reactants) formulated as L¹Ni(O₂CMe)·2H₂O (1), (L¹)₂Ni (2), and L²Ni·H₂O (3). HL¹ and H₂L² are the half unit and symmetric Schiff base ligands obtained from the (11) and (21) condensation of (Hina) with (o-phenen) respectively. The (11) molar ratio reaction of (1) with either acetylacetone (Hacac) or (Hina) in CHCl₃ led to the formation of mixed ligand complexes L¹Ni(acac)·H₂O (4) and L¹Ni(ina)·H₂O (5) whereas a similar reaction with salicylaldehyde (Hsal) produced L³Ni (6); H₂L³ is the unsymmetric Schiff base formed by the (11) condensation of the amino group in (1) with (Hsal). Analytical, spectral and magnetic moment evidence are compatible with the suggested structures of the metal complexes.This paper is a summary of the M.Sc. thesis of S. M. Imam.