Aluminum Complexes Research Articles

Aluminium complexes: next-generation catalysts for selective hydroboration.

Organoboranes obtained from hydroboration reactions are one of the important classes of compounds that could be used to provide valuable synthons for follow-up transformations such as various functional group incorporation or C-C bond forming reactions. For decades, various transition metals were utilised as catalysts in such transformations. Recently Earth-abundant and less toxic main group metals have revived their importance in hydroboration chemistry, among which the suitable candidates are aluminium complexes as catalysts. In this regard, the development of aluminium complexes to achieve more robust catalytic systems with greater efficiency is appreciable.

An insight into application and harmful effects of aluminium, aluminium complexes and aluminium nano-particles

Aluminium metal matrix compounds are attaining extensive undertakings for automobile, aerospace, farming equipment and many other industrial applications as their vital properties like immense strength, little density, excellent formability, good corrosion protection, good wear resistance correlated to other metals. This review paper deals with the inclusion of additional materials such as graphite, fly ash, silicon carbide, red mud, organic material, etc. in various proportions to the aluminium matrix to make it compatible for advanced uses. Each assisted material has its characteristic property which when combined improves the properties of the base alloy. It also includes the various complexes formed by aluminium, the role of aluminium nanoparticles in cancer therapies, remediation of pollutants, the interaction of nanoparticles with organisms and contaminants, and lastly Alzheimer’s disease as therapeutics. The increased use of nanoparticles in commercial and domestic applications prompts the emission of these harmful materials into the environment. In addition, the potential benefits of using nanoparticles, considering the specific sections of information related to their vulnerability to nanoparticles can have their applications in health and natural wellbeing. The investigation shows that aluminium compounds can be mixed with other traditional metals for superior implementation and durability.

Aluminium complexes containing indolyl-phenolate ligands as catalysts for ring-opening polymerization of cyclic esters.

A family of aluminium complexes supported by mono-anionic indolyl-phenolate ligands are described. Reactions of indolyl-phenolate based ligand precursors, IndHPhROH, with 1.0 or 0.5 equivalents of AlMe2Cl in toluene afforded aluminium indolyl-phenolate complexes 1-4 and aluminium bis-indolyl-phenolate complexes 5-8 respectively. The molecular structure is reported for 5. Based on the NMR spectroscopic and X-ray crystallographic studies, a 1,3-hydrogen shift could happen from nitrogen to carbon on the five-membered ring of the indolyl group upon reacting with aluminium reagents. These novel aluminium complexes demonstrate catalytic activities toward the ring-opening polymerization of cyclic esters in the presence of alcohol.

Modification of bidentate bis(N-heterocyclic imine) ligands for low-valent main group complexes

The synthesis of modified neutral bis-NHI (NHI is N-heterocyclic imine) ligands and their application for the stabilization of tetryliumylidenes are reported. The ligands’ scaffolding consists of either saturated or methylated imidazoline backbones, and the bridge alternated from flexible ethylene to more rigid o-phenylene. Transmetalation reactivity of the cationic SnII compounds was tested towards LiAlH4 and IDipp→SiCl2 [IDipp is 1,3-bis(2,6-diisopropyl- phenyl)imidazol-2-ylidene] affording the respective aluminium and silicon complexes.

Investigations into the structure, reactivity, and AACVD of aluminium and gallium amidoenoate complexes.

Amidoenoate (AME = {ethyl-3-(R-amido)but-2-enoate}) complexes of aluminium and gallium, of the type: [AlCl2(AMER)] R = iPr (1-Al); [AlCl(AMER)2] R = iPr (2-Al), Dip (3-Al); [GaCl2(AMER)] R = iPr (1-Ga) and [GaCl(AMER)2] R = iPr (2-Ga), Dip (3-Ga), have been synthesised (iPr = isopropyl, Dip = 2,6-diisopropylphenyl). The coordination chemistry of these complexes has been studied in relation to precursor suitability. Investigations into the reactivity of the aluminium and gallium amidoenoate complexes involved reactions with hydride sources including alkali metal hydride salts, alkylsilanes, and magnesium hydride species and magnesium(I) dimers. The isolation of alkyl metal amidoenoate precursors including an aluminium hydride amidoenoate, [AlH(AMEDip)2] (4-Al) and dimethyl gallium amidoenoates [GaMe2(AMEDip)] (4-Ga), [GaMe2(AMEiPr)] (5-Ga) concluded the synthetic studies. A selection of the isolated complexes were used as precursors for aerosol assisted chemical vapour deposition (AACVD) at 500 °C. Thin films of either amorphous Al2O3 or Ga2O3 were deposited and subsequently annealed at 1000 °C to improve the materials' crystallinity. The films were characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV-vis) spectroscopy and energy dispersive X-ray analysis (EDXA).

Komparativna analiza strategija glodanja površina složene geometrije

This paper analyses the influence of machining strategies and cutting parameters on the milling of aluminium complex geometry parts. In the first experimental phase, parts were machined with a combination of two roughing strategies and three finishing strategies, with recommended machining parameters. The machining time, machining surface roughness, and the surface geometric accuracy were measured. In the second phase, a new sample was machined with corrected cutting parameters using the best strategy adopted from the first phase. The results have shown that the selection of machining strategy and cutting parameters significantly affects the productivity, quality, and accuracy when machining complex geometry parts.

Synthesis of a polyaminocarboxylate-based aluminum complex and its structural studies using 1H{13C}-HMBC NMR and a Karplus-type function.

The HBED chelator is used to stabilize small and hard metal ions such as Fe3+, Ti4+, Ga3+ and Al3+ in both medicine and industry. While the coordination of hexadentate HBED4- is known in the case of Fe3+, Ti4+ and Ga3+, it is unknown in the case of the small Al3+ ion since its corresponding complex has never been fully characterized. Thus, in this work the coordination pattern in a newly synthesized aluminum HBED-based complex ([Al-HBED-NN]-Na+) was determined using 2D NMR in conjunction with DFT calculations.

Diverse reactivity of an iron-aluminium complex with substituted pyridines.

The reaction of an Fe–Al complex with an array of substituted pyridines is reported. Depending on the substitution pattern of the substrate site-selective sp2 or sp3 C–H bond activation is observed. A series of reaction products are observed based on (i) C–Al bond formation, (ii) C–C bond formation by nucleophilic addition or (iii) deprotonation of the β-diketiminate ligand. A divergent set of mechanisms involving a common intermediate is proposed.

A Mechanistic Study on Homo- and Copolymerization of L-Lactide and Ε-Caprolactone Catalyzed by an Aluminum Complex Bearing a Bis(Phenoxy)Amine Ligand: A Dft Study

A Mechanistic Study on Homo- and Copolymerization of L-Lactide and Ε-Caprolactone Catalyzed by an Aluminum Complex Bearing a Bis(Phenoxy)Amine Ligand: A Dft Study

Ring-Opening Polymerization of ε-Caprolactone and Styrene Oxide-CO2 Coupling Reactions Catalyzed by Chelated Dehydroacetic Acid-Imine Aluminum Complexes.

A series of chelated dehydroacetic acid–imine-based ligands L1H~L4H was synthesized by reacting dehydroacetic acid with 2-t-butylaniline, (S)-1-phenyl-ethylamine, 4-methoxylbenzylamine, and 2-(aminoethyl)pyridine, respectively, in moderate yields. Ligands L1H~L4H reacted with AlMe3 in toluene to afford corresponding compounds AlMe2L1 (1), AlMe2L2 (2), AlMe2L3 (3), and AlMe2L4 (4). All the ligands and aluminum compounds were characterized by IR spectra, 1H and 13C NMR spectroscopy. Additionally, the ligands L1H~L4H and corresponding aluminum derivatives 1, 3, and 4 were characterized by single-crystal X-ray diffractometry. The catalytic activities using these aluminum compounds as catalysts for the ε-caprolactone ring-opening polymerization (ROP) and styrene oxide-CO2 coupling reactions were studied. The results show that increases in the reaction temperature and selective solvent intensify the conversions of ε-caprolactone to polycaprolactone. Regarding the coupling reactions of styrene oxide and CO2, the conversion rate is over 90% for a period of 12 h at 90 °C. This strategy dispenses the origination of cyclic styrene carbonates, which is an appealing concern because of the transformation of CO2 into an inexpensive, renewable and easy excess carbon feedstock.

Five-coordination aluminum complexes: Synthesis, crystal structures and utilization for the construction of substituted guanidines

Insertion of 2,6-iPr2C6H3N(Li)SiMe3 or PhN(Li)SiMe3 to the CN bond of Me2NCN or PhCN afforded the lithium complexes [Li(2,6-iPr2C6H3)NC(NMe2)NC(NMe2)N(SiMe3)]2 (1a) and [Li(PhNC(Ph)NSiMe3)]2 (1b). Complexes 1a and 1b were used as precursors to react with AlCl3 affording [(2,6-iPr2C6H3)NC(NMe2)NC(NMe2)N(SiMe3)]2AlCl (2) and [(PhNC(Ph)NSiMe3)]2AlCl (3), respectively. The structures of 2 and 3 were presented. Both 2 and 3 exhibit good activity to catalyze the addition reaction of arylamines to N,N'-diisopropylcarbodiimide.

Lactide Lactone Chain Shuttling Copolymerization Mediated by an Aminobisphenolate Supported Aluminum Complex and Al(OiPr)3: Access to New Polylactide Based Block Copolymers.

The chain shuttling ring-opening copolymerization of l-lactide with ε-caprolactone has been achieved using two aluminum catalysts presenting different selectivities and benzyl alcohol as chain transfer agent. A newly synthesized aminobisphenolate supported aluminum complex affords the synthesis of lactone rich poly(l-lactide-co-lactone) statistical copolymeric blocks, while Al(OiPr)3 produces semicrystalline poly(l-lactide) rich blocks. Transalkoxylation is shown to operate efficiently. The crystalline ratios and glass transition temperatures of these new classes of polylactide based block copolymers can be tuned by adjusting the catalysts and the comonomers ratio.

Indium-Catalyzed CO2/Epoxide Copolymerization: Enhancing Reactivity with a Hemilabile Phosphine Donor.

Group 13 metal complexes have emerged as powerful catalysts for transforming CO2 into added-value products. However, direct comparisons of reactivity between Al, Ga, and In catalysts are rare. We report aluminum (1), gallium (2), and indium (3) complexes supported by a half-salen H[PNNO] ligand with a pendent phosphine donor and investigate their activity as catalysts for the copolymerization of CO2 and cyclohexene oxide. In solution, the P-donor is dissociated for the Al and Ga complexes while for the In complex it exhibits hemilabile behavior. The indium complex shows higher conversion and selectivity than the Al or Ga analogues. The mechanism of the reaction was studied by NMR and FTIR spectroscopy experiments as well as structural characterization of off-cycle catalytic intermediate indium trichloride complex [(PNNO)InCl3][TBA] (4). This study highlights the impact of a hemilabile phosphine group on group 13 metals and provides a detailed analysis of the initiation step in CO2/epoxide copolymerization reactions.

Methylaluminum complexes based on tridentate 2,6-bis(mercaptoalkyl)pyridine SNS-ligands

New SNS-ligands were obtained by consequent ring-opening of substituted thiiranes by lithiated 2,6-lutidine, mono- functionalized SN-ligands having been isolated as the intermediate compounds. The molecular structure of ligand 2,6-Py(CH2CH2CBn2SH)2 was elucidated by XRD analysis.The reaction of AlMe3 with SNS-ligands afforded monomeric methyl aluminum complexes which have been tested in ring- opening polymerization of ε caprolactone in bulk.

Charred plant fragment–aluminium complexes in buried humic horizons of a cumulative volcanic soil profile: Formation, accumulation and potential role

AbstractThe objective of the present study was to investigate the formation, accumulation and potential role of charred plant fragment (CPF)–aluminium (Al) complexes in several buried A (Ab) horizons of a cumulative volcanic soil profile, focusing on CPFs, active Al components and soil age. Nineteen soil samples were collected from four buried humic horizons (2A–5A, from 7.3 cal ka BP to AD 1471), and their CPF–carbon (C), soil organic C (SOC), acid oxalate‐extractable Al (Alox), pyrophosphate‐extractable Al (Alpy, Al–humus complexes) and short‐range ordered Al minerals (Alox − Alpy) were quantified. The proportion of CPF–C content (up to 15.8 g kg−1) to SOC content (up to 117 g kg−1) ranged from 2.3% to 15.1% (8.4% on average). The contents of active Al components (6.71–77.1 g kg−1) increased: Alpy < Alox − Alpy < Alox. No consistent trends with age were found for the accumulation levels of CPF–C, SOC and active Al components. However, significant positive correlations (p < 0.001) were found between the Alpy and CPF–C and SOC contents, suggesting that the accumulation and stabilisation of soil organic matter in these humic layers proceeded simultaneously with the formation of organo–Al complexes, including CPF–Al complexes. On the other hand, significant negative correlations (p < 0.01) were obtained between the Alox − Alpy and Alpy, CPF–C or SOC contents. From these correlations, it was assumed that the complexation of organic constituents, including CPFs, with Al competed with the synthesis of short‐range ordered Al minerals (including allophane and imogolite), irrespective of soil age and climatic conditions with the range of more than 6000 years. This competitive relationship in the presence of CPFs was first described in the current study.Highlights Significance of charred plant fragment–aluminium complexes in humic horizons was discussed. There were no consistent trends with age for the accumulation levels of organic constituents. The accumulation of organic matter proceeded simultaneously with the formation of the complexes. The formation of the complexes competed (>6000 years) with the synthesis of aluminium minerals.

Aluminum(III), iron(III) and copper(II) complexes of luteolin: Stability, antioxidant, and anti-inflammatory properties

In this work complexation of luteolin (H4Lu) with Al(III), Fe(III) and Cu(II) at 37 °C and in 0.16 M NaCl is discussed. To evaluate the competition of the ligand for the metal cations and H+, the protonation constant of luteolin was also determined under the same experimental conditions. Speciation profiles obtained by potentiometric titrations show that in aqueous solution a complexation occurs at 1:1 ligand-to-Al(III) ratio, and at 1:1 and 2:1 ligand-to-cation ratios for Fe(III) and Cu(II). The coordination sites of luteolin to the different metal ions were determined by a computational approach, displaying that copper ion shows no selective preference towards any of the complexation sites of luteolin, while the six-membered chelate ring of the 4–5 site (i.e., the 4-carbonyl-5-hydroxyl site of the A and C rings of the ligand) is the preferred one for aluminum and iron ions. Additionally, we have evaluated the antioxidant and anti-inflammatory properties of free luteolin and of the luteolin-metal ion complexes. The complex with iron was found to have a higher activity than the other complexes (i.e., Fe(III)-Lu > Cu(II)-Lu > Al(III)-Lu), and its DPPH radical scavenging ability was even higher than that of free luteolin. Finally, all luteolin metal complexes were found to significantly reduce lipopolysaccharide (LPS)-induced interleukin (IL)-6 levels in monocyte-derived macrophages with the following order: Fe(III)-Lu > Al(III)-Lu > Cu(II)-Lu > free Lu.

Mono- and di-phosphine oxide complexes of aluminium, gallium and indium with weakly coordinating triflate anions – Synthesis, structures and properties

Reaction of the Group 13 triflates, M(OTf)3 (M = Al, Ga, In; OTf = CF3SO3−), with 3 mol. eq. of R3PO (R = Ph or Me) gives the six-coordinate complexes, [M(OTf)3(R3PO)3], with coordinated triflate, as white powdered solids. Similarly, using 3 mol. eq. of PyNO (pyridine-N-oxide) readily forms [In(OTf)3(PyNO)3], whose crystal structure confirms a mer octahedral arrangement. In contrast, reaction of the harder Lewis acids Al(III) and Ga(III) with PyNO produce mixtures, mostly likely of the 3:1 and 4:1 species, [M(OTf)3(PyNO)3] and [M(OTf)2(PyNO)4][OTf] (M = Al, Ga). Both of the tetrakis species have been confirmed via single crystal X-ray studies and shown to exist as trans isomers. Higher ratios (4:1, 5:1 and 6:1) of Me3PO coordinated to In(OTf)3 can also be achieved by varying the reaction stoichiometry appropriately, with the coordinated OTf groups readily displaced by the Me3PO.Crystal structures of two polymorphs of the salt, [In(OTf)2(Me3PO)4][In{(OH2)2(OTf)4}(Me3PO)4], in which the [In{(OH2)2(OTf)4}(Me3PO)4]− anion is (unusually) comprised of a ‘InIII(OH2)2(Me3PO)4′ unit with four OTf anions H-bonded to the aquo ligands, giving the overall monoanionic charge. A similar arrangement is present in [In(OTf)2(Ph3PO)4][In{(OH2)4(OTf)4}(Ph3PO)2], the structure of which shows that all of the H atoms associated with the four aquo ligands in the [In{(OH2)4(OTf)4}(Ph3PO)2]− form significant H-bonds to the OTf groups; specifically, the four OTf− anions each show two O⋯H interactions, forming bridges that link the equatorial aquo ligands into a 24-membered ‘pseudo-macrocyclic’ ring. The crystal structure of the mononuclear 5:1 complex, [Ga(Me3PO)5(MeCN)][OTf]3, is also described.Using the diphosphine dioxide, dppmO2 (Ph2P(O)CH2P(O)Ph2), with M(OTf)3 in a 3:1 ratio readily affords the tris-chelate species, [M(dppmO2)3][OTf]3 for all three metals, while a 2:1 ratio also gives [Ga(OTf)2(dppmO2)2][OTf]. Crystal structures of both [Al(dppmO2)3][OTf]3·MeCN and [Ga(dppmO2)3][OTf]3·2CHCl3 are reported.Multinuclear (1H, 13C{1H}, 19F{1H}, 31P{1H}, 27Al, 71Ga and 115In, where appropriate) NMR data show that in CD3CN the complexes are labile and the different R3PO coordination environments are not distinguished (although exchange between coordinated and ‘free’ Me3PO is slow on the 31P NMR timescale), while the MeCN solvent also replaces OTf in the metal coordination sphere.

Diamidoamine Aluminum Complexes: Synthesis, Structure, L–Lactide and ϵ‐Caprolactone Polymerization

AbstractA series of methyl and chlorido aluminum complexes decorated with diamidoamine ligands with different number of carbon atoms in the alkyl chains were prepared via methane elimination, salt methatesis route, transmetallation strategy or chlorination. They were investigated by various methods including 19F, 27Al NMR spectroscopy and showed to be active catalysts of ring‐opening polymerization of ϵ‐Cl and L−La.

Yellow Emissive Tris(8-hydroxyquinoline) Aluminum by the Incorporation of ZnO Quantum Dots for OLED Applications.

Tris(8-hydroxyquinoline) aluminum complexes are of significant interest because of their remarkable optical and electrical properties, both as an emissive layer and electron injection layer. They emit light in the blue and green ranges of the visible spectrum, so for white organic light emitting diodes (OLEDs), yellow emission is required as well. In this study, we propose the use of zinc oxide quantum dots to tune the emission color of the complex while maintaining its luminous efficiency. Hence, tris(8-hydroxyquinoline) aluminum-zinc oxide nanohybrids with different zinc oxide quantum dots concentrations (10, 20, or 30 wt.%) were synthesized. The structural properties were characterized using powder X-ray diffraction analysis, while the composition and optical characteristics were characterized by Fourier transform infrared spectroscopy, UV-visible absorption spectroscopy, and photoluminescence emission spectroscopy. The results show that increased levels of zinc oxide quantum dots lead to a decrease in crystallinity, double hump emission and a slight red shift in emission peaks. Also, at 20 and 30 wt.% of zinc oxide quantum dots concentrations, yellow emission was observed.

Experimental Study on Preventing Formation Damage Due to Clay Swelling Caused by Water Based Drilling Fluid Using Aluminum Ion Based Clay Inhibitor

Formation damage is an unfavorable challenge that occurs during drilling. The present study reports applicability of aluminum complex (AC, the combination between Al ion of aluminum sulfate (AS) and ethylenediaminetetraacetic (EDTA)) as a permanent clay swelling inhibitor in water-based drilling fluids. That used to reduce formation damage in the near wellbore. This complex is an environmentally friendly and inexpensive additive in water-based drilling fluids (WBDFs) as a clay swelling inhibitor. Some experiments were performed in this study including free swelling test, bentonite sedimentation test, compatibility test, and core flood analysis. The results showed that AC solution can act properly as a clay swelling inhibitor at optimal concentration of AC around 5.4%wt. More than, compatibility test indicated that AC additive is compatible with other common additives in WBDF. The results show adding 8.1 wt.% of AC solution have lowest permeability reduction compared to other concentrations. More than, core flooding results showed AC solution can act as permanent clay inhibitor compared to KCl that is a temporary inhibitor. The AC solution performance was not much sensitive to salinity.