Dimethyl Aluminum Research Articles

Contrasting a series of bidentate amido phosphine oxide, sulfide, or selenide ligands and complexes of dimethyl aluminum and indium.

A series of EP(V)-imine phosphine-imine ligands (Dipp-NC(CH3)-(CH2)-PE(Ph2)) (Dipp = 2,6-diisopropylphenyl, E = O, S, Se) and corresponding dimethyl aluminum and indium complexes were prepared and characterized using multi-nuclear NMR spectroscopy and SC-XRD. Solution-state 1H and 31P NMR spectroscopy indicate a mixture of isomers in solution (C6D6, CDCl3, and CD3CN). Solid state structures of both the imine and (E)-enamine isomers of the oxygen-based ligand have been observed. These three ligands (L) were then deprotonated with M(CH3)3 (M = Al or In), with methane loss forming a 6-membered ring via bidentate chelation ((κ2-L)M(CH3)2). The indium/oxide complex also crystallized as a 12-membered ring.

Study on the Structure, Thermodynamic property, and Fluorescence of Pyridin‐2‐ylmethyl‐tert‐butylamine Dimethyl aluminum complex

AbstractPyridin‐2‐ylmethyl‐tert‐butylamine dimethyl aluminum complex with a planar five‐membered ring was synthesized and characterized by elemental analysis, UV‐Vis spectra, TG/DSC, 1H NMR, and 13C NMR. Through single‐crystal diffraction, it is proved that the structure of the alkyl aluminum complex is a planar five‐membered ring. By comparison the crystal data of 11 kinds of five‐membered ring dialkyl aluminum complexes, we found that the planar five‐membered ring dialkyl aluminum is formed when there is at least one unequal sp2 hybrid nitrogen in the ligand. TG/DSC study of the compound′s thermodynamic properties showed the thermal decomposition temperature of complex 7 was determined to be 210 °C. The rigid plane structure of the product was proved by fluorescence analysis. When the excitation wavelength was 380 nm, the emission wavelength was 478 nm.

Thermo-Rheological and Shape Memory Properties of Block and Random Copolymers of Lactide and ε-Caprolactone.

Biodegradable block and random copolymers have attracted numerous research interests in different areas, due to their capability to provide a broad range of properties. In this paper, an efficient strategy has been reported for preparing biodegradable PCL-PLA copolymers with improved thermal, mechanical and rheological properties. Two block-copolymers are synthesized by sequential addition of the cyclic esters lactide (L-LA or D,L-LA) and ε-caprolactone (CL) in presence of a dimethyl(salicylaldiminato)aluminium compound. The random copolymer of L-LA and CL was synthetized by using the same catalyst. Chain structure, molar mass, thermal, rheological and mechanical properties are characterized by NMR, SEC, TGA, DSC, Rheometry and DMTA. Experimental results show that by changing the stereochemistry and monomer distribution of the copolymers it is possible to obtain a variety of properties. Promising shape-memory properties are also observed in the di-block copolymers characterized by the co-crystallization of CL and L-LA segments. These materials show great potential to substitute oil-based polymers for packaging, electronics, and medicine applications.

Synthesis and characterization of group 13 dichloride (M = Ga, In), dimethyl (M = Al) and cationic methyl aluminum complexes supported by monoanionic NNN-pincer ligands

A series of monoanionic NNN-pincer ligands effectively stabilize five-coordinate gallium and indium dichloride complexes, as well as neutral dimethyl aluminum species, and organometallic cations thereof.

Heteroleptic lead and aluminium complexes ligated by a bulky non-symmetrical triazenide

The sterically bulky non-symmetrical triazene, DmpN3(H)Dipp∗, was prepared. Amido lead triazenide and dimethyl aluminium triazenide complexes were readily prepared by metalation of the parent triazene. The former is a rare example of a stable heteroleptic lead triazenide complex. Analogous compounds are inaccessible when smaller triazenes are employed under these conditions, as they readily form homoleptic bis(aryl)triazenide complexes. Quantification of the bulk of this and other bidentate monoanionic N,N′-donor ligands, using the solid-state structures of model dimethyl aluminium complexes, help to rationalize the superior stability of the amido lead triazenide complex reported herein with regards to subsequent metalation.

ВЛИЯНИЕ МОДИФИКАТОРОВ НА ВРЕМЯ ОТВЕРЖДЕНИЯ ФЕНОЛОФОРМАЛЬДЕГИДНОГО СВЯЗУЮЩЕГО ДЛЯ ПРЕССОВАНИЯ ФАНЕРЫ ПРИ НИЗКОТЕМПЕРАТУРНОМ РЕЖИМЕ

Volumes of plywood production with increased water resistance for indoor and outdoor use (FSF brand) are increasing in Russia. The demand for it in the country and in the world continues to grow. The phenol-formaldehyde oligomer during the curing process passes through the stages of resol, resitol and resite. Ensuring long-term water resistance of plywood is possible only if the resite stage is reached and the solidified phenol-formaldehyde resin (FFR) reaches non-melting and insoluble state. The problem is that the industrial process of FSF plywood pressing is carried out in the rezitol temperature range. In literature, there are conflicting data on the temperature ranges of the stages of the FSF polycondensation process. The authors have proposed to operate with scientific data on the temperature ranges of FFR curing, confirmed by the results of spectroscopic studies. It is necessary to develop phenol-formaldehyde binder compositions capable of curing to the resite stage at lower pressing temperatures than unmodified FSF to ensure the necessary operational characteristics of FSF plywood. In this study, a number of modifiers have been proposed that potentially reduce the time it takes to press plywood at low temperatures. The gelatinization time of the phenol-formaldehyde binder based on the SFZh-3014 resin (according to 20907-2016 State Standard) and modifying additives (hydrogen peroxide, eight-water zinc sulfate, ammonium alum, anhydrous magnesium chloride, six-water iron chloride, six-water aluminum chloride, aluminum dimethyl sulfate, dimethyl glyoximate, and sulfate, sulfosalicylic two-water acid) have been determined. A study of the gelatinization process in the presence of a large number of modifying additives (more than 1.5%) revealed a significant deterioration in the spreadability of the binder. Therefore, it is recommended to use FFR curing accelerators in the amount not exceeding 1-1.5%.

The Effect of Al2O3 ALD Precursors on the Electrochemical Performance of Cathode Materials for Lithium-Based Battery Applications

Al2O3 coatings prepared by atomic layer deposition (ALD) using trimethyl aluminum (TMA) and H2O on various cathode materials have been shown to enhance the battery cycle stability of lithium ion batteries. Interestingly, not all cathode materials are enhanced by Al2O3 ALD coating. For example, while Al2O3 coating on lithium cobalt oxide (LCO) using 1-2 TMA/H2O ALD cycles dramatically improves cycle performance [1], much less positive effect on lithium manganese oxide (LMO) was observed [2]. We revealed the TMA surface reactions on LMO are unusual in that they do not involve hydroxyls, ethane is released, and the manganese undergoes redox chemistry from our previous study [2]. Furthermore, density functional theory (DFT) calculations reveal that this unique mechanism is driven by the large free energy changes upon methyl loss from TMA [2]. This information leads us to speculate that the surface reactions and subsequent electrochemistry might also depend on different Al precursors. To evaluate our hypothesis, we are exploring a range of aluminum precursors including trimethyl aluminum (TMA), tris(dimethylamido) aluminum (Al-TDMA), aluminum trichloride (AlCl3), dimethyl aluminum isopropoxide (DMAI), and aluminum triisopropoxide (ATIP) on LCO and LMO cathode materials. Our preliminary results showed that very different ALD chemistries on between LCO and LMO cathode materials. It suggests a correlation between cation reduction on the cathode surface and the relative Lewis acidity of the Al precursor ligands. We will elaborate on these findings using results from XPS measurements, DFT calculations, electrochemical characterizations, and battery cycling studies. [1] Y. S. Jung et. al., J. Electrochem. Soc. 157 (1) A75-A81, (2010). [2] L. Chen et. al., Chem 4 2418-2435 (2018).

Flexible Coordination of N,P-Donor Ligands in Aluminum Dimethyl and Dihydride Complexes.

Aluminum hydrides, once a simple class of stoichiometric reductants, are now emerging as powerful catalysts for organic transformations such as the hydroboration or hydrogenation of unsaturated bonds. The coordination chemistry of aluminum hydrides supported by P donors is relatively underexplored. Here, we report aluminum dihydride and dimethyl complexes supported by amidophosphine ligands and study their coordination behavior in solution and in the solid state. All complexes exist as κ2-N,P complexes in the solid state. However, we find that for amidophosphine ligands bearing bulky aminophosphine donors, aluminum dihydride and dimethyl complexes undergo a “ligand-slip” rearrangement in solution to generate κ2-N,N complexes. Thus, importantly for catalytic activity, we find that the coordination behavior of the P donor can be modulated by controlling its steric bulk. We show that the reported aluminum hydrides catalyze the hydroboration of alkynes by HBPin and that the variable coordination mode exhibited by the amidophosphine ligand modulates the catalytic activity.

Quickly self-extinguishing flame retardant behavior of rigid polyurethane foams linked with phosphaphenanthrene groups

In order to explore the high-performance rigid polyurethane foams (RPUFs) with excellent flame-retardant efficiency, a reactive-type phosphaphenanthrene compound TGD was linked with RPUF matrix while the addition-type flame retardants dimethyl methylphosphonate (DMMP), aluminum hydroxide (ATH) and expandable graphite (EG) were mixed into RPUF composites. The constructed flame retardant system in RPUF materials caused that a quickly self-extinguishing effect on flame were formed and the flame extinguished in just 49s during cone calorimeter test. Besides the quickly self-extinguishing effect, the flame retardant system also brought the higher limited oxygen index, the lower peak of heat release rate (pk-HRR), the less total heat release, the more residue yields. The quickly self-extinguishing effect and excellent flame retardancy of the system were caused by the continuously quenching effect from TGD and DMMP in gas phase, and by the jointly charring effect from TGD and EG/ATH, and also by the reduced fuels because TGD and other flame retardants jointly locked more carbonaceous contents in residue. The quickly self-extinguishing effect and flame retardancy from TGD/DMMP/EG/ATH system put forward a novel effective way to solve the fire-proof safety of RPUF thermal-insulating materials.

Understanding the Effects of Ultra-Thin Al2O3 Coatings Prepared By Atomic Layer Deposition on Lithium Ion Battery Cathode Materials

Although various cathode materials possessing high capacity have been developed to date, most of them are still suffering from early capacity fading. Several strategies such as doping, surface treatment and coating have been adopted to minimize this problem. Among a variety of coating strategies, atomic layer deposition (ALD) is regarded as the best technique for coating of cathode materials. ALD is a thin-film growth technique that offers the unique capability to coat complex, three-dimensional objects with precise, conformal layers by atomic-level control over thickness and composition. Over the last decade, ALD has emerged as an effective strategy for coating cathode materials to enhance the overall performance Li-ion batteries. ALD Al2O3 coatings prepared using trimethyl aluminum (TMA) and H2O have been evaluated previously on cathodes including LiCoO2 (LCO), LiMn2O4 (LMO), and Li(NixMnyCoz)O2 (NMC), and the effect of the coating on cycling stability was found to vary between these different materials. Moreover, our recent study of TMA/H2O chemistry on LMO revealed a unique nucleation mechanism leading to unexpected products and altered electrochemical behavior. In an effort to better understand these observations, we are exploring Al2O3 ALD using a range of aluminum precursors (TMA, tris(dimethylamido) aluminum, aluminum trichloride, dimethyl aluminum isopropoxide, and aluminum triisopropoxide) and a variety of cathode materials (LCO, LMO, and several NMCs). We discovered that the ALD aluminum precursor reduces cations on the cathode surface, and the degree of reduction depends on the relative Lewis acidity of the precursor ligands, and on the composition of the cathode surface. In this presentation we will elaborate on these findings and describe the correlations between the chemistry of the ALD-modified cathode surface and the resulting electrochemical behavior and cycling performance.

Amorphous Alumina Films Efficiently Protect Ti6242S against Oxidation and Allow Operation above 600 °C

The protection of the titanium based Ti6242S alloy against oxidation at moderate temperature is investigated, through the application on its surface of a 300 nm thick, amorphous alumina film. The latter is processed by metalorganic chemical vapor deposition at 500 °C from dimethyl aluminum isopropoxide. Upon oxidation at 600 °C for 5000 h, an interfacial zone is created between the alloy and the external protective layer, composed of unaffected alumina. In these conditions, the mass gain per unit area is eight times lower than that of the bare alloy, while the hardness of the alloy remains unaffected, revealing negligible oxygen ingress attributed to the efficiency of the protective coating. Finally, alumina coated samples show negligible mass change after 80 one-hour thermal cycles between 50 °C and 600 °C, showing excellent coating adherence on the Ti alloy.

Influence of carbon impurities and oxygen vacancies in Al2O3 film on Al2O3/GaN MOS capacitor characteristics

Effects of carbon impurities and oxygen vacancies in Al2O3 film on the characteristics of Al2O3/GaN MOS capacitors were studied using the different atomic layer deposition (ALD) precursor and high-pressure water vapor annealing (HPWVA). Trimethyl aluminum (TMA: Al(CH3)3) and dimethyl aluminum hydride (DMAH: Al(CH3)2H) were used as ALD precursors to control the carbon impurities. On the other hand, oxygen vacancies in Al2O3 film were suppressed using the HPWVA. The DMAH precursor reduced the concentration of carbon impurities in the ALD Al2O3 film. It was found that the interface trap density (Dit) was mainly affected by the carbon impurities rather than the oxygen vacancies at the Al2O3/GaN interface. On the other hand, voltage stress induced flat band voltage (VFB) shift was attributed to both the carbon impurities and the oxygen vacancies.

Effects of Dimethyl Methylphosphonate, Aluminum Hydroxide and Ammonium Polyphosphate on the Flame Retardancy and Thermal Properties of Unsaturated Polyester Resin

The flame-retardant unsaturated polyester resin with dimethyl methylphosphonate (DMMP), aluminum hydroxide (ATH) and ammonium polyphosphate (APP) were prepared and found to exhibit a high flame-retardant efficiency and low cost. The different dosages of flame retardant effect on the flame retardant were evaluated based on limiting oxygen index (LOI) measurements, vertical burning test (UL94), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). A LOI value of 29.8% and a UL-94 vertical burning V-0 rating was achieved for UPR with 10phr DMMP, 15phr ATH and 9phr APP. In the presence of DMMP, ATH and APP, the dense char structure were produced in the combustion process of UPR.

Broadband optical properties of aluminium zinc oxide thin films prepared by spatial atomic layer deposition

In this work, a broadband ellipsometric investigation of aluminium zinc oxide (AZO) from the infrared to the ultraviolet spectral range is presented. Aluminium zinc oxide samples were fabricated using spatial atomic layer deposition (SALD) having a range of percent aluminium incorporation. The AZO was deposited using a coflow of diethyl zinc (DEZ) and dimethyl aluminium isopropoxide (DMAI), where the amount of aluminium incorporation was controlled by varying the DMAI partial pressure. The broadband permittivity is reported as a function of the aluminium content of these aluminium zinc oxide thin films. A model dielectric function, which includes the contribution of recently predicted broad shallow donor states, is presented and discussed. We find that an increase in the aluminium content of the aluminium zinc oxide thin films results in a monotonically decreasing scattering time while the carrier density increases with diminishing efficiency. To demonstrate the necessity of broadband ellipsometric measurements for the accurate determination of the dielectric function of aluminium zinc oxide, a comparison with the classical Drude model and a semi-empirical extended Drude dispersion model, which are frequently employed in the literature to describe the optical response of aluminium zinc oxide, is given.

PEALD of SiO2 and Al2O3 Thin Films on Polypropylene: Investigations of the Film Growth at the Interface, Stress, and Gas Barrier Properties of Dyads.

A study on the plasma-enhanced atomic layer deposition of amorphous inorganic oxides SiO2 and Al2O3 on polypropylene (PP) was carried out with respect to growth taking place at the interface of the polymer substrate and the thin film employing in situ quartz-crystal microbalance (QCM) experiments. A model layer of spin-coated PP (scPP) was deposited on QCM crystals prior to depositions to allow a transfer of findings from QCM studies to industrially applied PP foil. The influence of precursor choice (trimethylaluminum (TMA) vs [3-(dimethylamino)propyl]-dimethyl aluminum (DMAD)) and of plasma pretreatment on the monitored QCM response was investigated. Furthermore, dyads of SiO2/Al2O3, using different Al precursors for the Al2O3 thin-film deposition, were investigated regarding their barrier performance. Although the growth of SiO2 and Al2O3 from TMA on scPP is significantly hindered if no oxygen plasma pretreatment is applied to the scPP prior to depositions, the DMAD process was found to yield comparable Al2O3 growth directly on scPP similar to that found on a bare QCM crystal. From this, the interface formed between the Al2O3 and the PP substrate is suggested to be different for the two precursors TMA and DMAD due to different growth modes. Furthermore, the residual stress of the thin films influences the barrier properties of SiO2/Al2O3 dyads. Dyads composed of 5 nm Al2O3 (DMAD) + 5 nm SiO2 exhibit an oxygen transmission rate (OTR) of 57.4 cm3 m-2 day-1, which correlates with a barrier improvement factor of 24 against 5 when Al2O3 from TMA is applied.

Experimental study of trimethyl aluminum decomposition

Trimethyl aluminum (TMA) is an important precursor used for metal-organic chemical vapor deposition (MOCVD) of most Al-containing structures, in particular of nitride structures. The reaction mechanism of TMA with ammonia is neither clear nor certain due to its complexity. Pyrolysis of trimethyl metal is the start of series of reactions, thus significantly affecting the growth. Experimental study of TMA pyrolysis, however, has not yet been conducted in detail. In this paper, a reflectron time-of-flight mass spectrometer is adopted to measure the TMA decomposition from room temperature to 800°C in a special pyrolysis furnace, activated by soft X-ray from the synchrotron radiation. The results show that generation of methyl, ethane and monomethyl aluminum (MMA) indicates the start of the pyrolysis process. In the low temperature range from 25°C to 700°C, the main product is dimethyl aluminum (DMA) from decomposition of TMA. For temperatures larger than 700°C, the main products are MMA, DMA, methyl and ethane.

Titanium, aluminum and zinc complexes containing diamine-bis(benzotriazole phenolate) ligands: Synthesis, structural characterization and catalytic studies for ring-opening polymerization of ε-caprolactone

Structurally diverse metal complexes bearing diamine-bis(benzotriazole phenolate) (DiBTP) ligands have been synthesized and fully characterized by single crystal X-ray crystallography. The reaction of Ti(OiPr)4 with C8MEADiBTP-H2 or C8BEADiBTP-H2 (1.0 mol equiv.) generated the monomeric titanium alkoxy complexes [(C8MEADiBTP)Ti(OiPr)2] (1) and [(C8BEADiBTP)Ti(OiPr)2] (2), respectively. Moreover, C8BEADiBTP-H2 reacted with 2.0 molar equiv. of AlMe3 to give the tetra-coordinated di-aluminum complex [(C8BEADiBTP)Al2Me4] (3). Zinc complex [(C8BEADiBTP)Zn2Et2] (4) could be obtained by the alkane elimination of ZnEt2 (2.0 equiv.) with C8BEADiBTP-H2 as the pro-ligand under similar synthetic methods in good yield. Single-crystal X-ray diffraction indicates that 3 is a bimetallic aluminum dimethyl complex with a tetradentate C8BEADiBTP moiety chelating two metal atoms, whereas complex 4 displays the dinuclear feature containing both tetra- and penta-coordinated zinc atoms bonded by one ONNON-pentadentate C8BEADiBTP ligand. Catalytic studies for ring-opening polymerization of ε-caprolactone of complex 1–4 were systematic explored; the comparative studies of such polymerization were also discussed.

Quinolyl‐Amidinates Chelating Bimetallic Magnesium and Mononuclear Aluminum Complexes for ϵ‐Caprolactone Polymerization

AbstractA series of quinolyl‐amidinate compounds ((Ar–N=C(Ph)–N(H)–C9H5N–2–Me: Ar=2,6‐Me2C6H3 (L1), 2,6‐Et2C6H3 (L2), 2,6‐iPr2C6H3 (L3), 2,4,6‐Me3C6H2 (L4), 2,6‐Et2‐4‐MeC6H2 (L5)) was synthesized. These compounds in toluene reacted with C2H5MgBr forming the bimetallic bromomagnesium complexes (Mg1 ‐ Mg5) in high yields, and with AlMe3 producing dimethyl aluminum complexes (Al1 ‐ Al5) in high yields. All organic compounds and their corresponding magnesium and aluminum complexes were characterized by elemental and spectroscopic analyses. The ambiguous structures of complexes Mg2, Mg5 and Al1 were determined by the single crystal X‐ray diffraction analysis, reflecting bimetallic feature of complexes Mg2 and Mg5 with five‐coordination around magnesium atoms and mononuclear aluminum complex Al1 as a distorted trigonal‐bipyramidal geometry. All magnesium and aluminum complexes initiate the ring opening polymerization of ϵ‐caprolactone with good conversion yields. Aluminum complexes showed better activity with TOF up to 3678 h−1 at 80 °C in the presence of BnOH, while bromomagnesium complexes attained the good conversion of ϵ‐CL without of BnOH.

Atomic Layer Deposition of Al2O3 Thin Films Using Dimethyl Aluminum sec-Butoxide and H2O Molecules

Aluminum oxide (Al2O3) thin films were grown by atomic layer deposition (ALD) using a new Al metalorganic precursor, dimethyl aluminum sec-butoxide (C12H30Al2O2), and water vapor (H2O) as the reactant at deposition temperatures ranging from 150 to 300 oC. The ALD process showed typical self-limited film growth with precursor and reactant pulsing time at 250 oC; the growth rate was 0.095 nm/cycle, with no incubation cycle. This is relatively lower and more controllable than the growth rate in the typical ALD-Al2O3 process, which uses trimethyl aluminum (TMA) and shows a growth rate of 0.11 nm/ cycle. The as-deposited ALD-Al2O3 film was amorphous; X-ray diffraction and transmission electron microscopy confirmed that its amorphous state was maintained even after annealing at 1000 oC. The refractive index of the ALD-Al2O3 films ranged from 1.45 to 1.67; these values were dependent on the deposition temperature. X-ray photoelectron spectroscopy showed that the ALD-Al2O3 films deposited at 250oC were stoichiometric, with no carbon impurity. The step coverage of the ALD-Al2O3 film was perfect, at approximately 100%, at the dual trench structure, with an aspect ratio of approximately 6.3 (top opening size of 40 nm). With capacitance-voltage measurements of the Al/ALD-Al2O3/p-Si structure, the dielectric constant of the ALDAl2O3 films deposited at 250 oC was determined to be ~8.1, with a leakage current density on the order of 10−8 A/cm2 at 1 V.

Synthesis and performance of star-shaped aluminum phosphinate flame retardant

A star-shaped aluminum dimethyl(2,2-dimethyl-1,3-propylene)bis(oxy)bicarbonylethyldiphos phinate (AlCP) was synthesized by esterifying reaction between 2-methy-2,5-dioxo-1,2-oxaphospholane (OP) and neopentyl glycol following by neutralizing with aluminum hydroxide. The structure and composition were confirmed with FTIR, 1H NMR, 31P NMR and X-ray fluorescent spectroscopy. AlCP begins to decompose at 370 °C, matching the initial decomposition temperature of PBT. It endows PBT with desired flame retardancy and anti-dripping property and shows good compatibility with PBT. When the total filler loading is kept at 17, 15–13 mass% AlCP combining with 2–4 mass% MC can make the PBT passing the UL 94 V0 rating and eliminating dripping. In addition, the AlCP has a little influence on the mechanical properties of PBT. The tensile strength and notched impact strength of PBT containing 17 mass% AlCP only reduce by 5.6 and 4 %, respectively, comparing to the pure PBT. The SEM photographs show that AlCP has a good compatibility with PBT. Microcombustion calorimeter, TG-FTIR and SEM results show that AlCP can depress the heating release and promote char forming during combustion and acts mainly in the condensed phase.