Highly efficient microwave-accelerated preparation of β-ketoimines

Tris(β-ketoiminate) Aluminium(III) Compounds as Aluminium Oxide Precursors

Precursor design is the crucial step in tailoring the deposition profile towards a multitude of functional materials. Most commercially available aluminium oxide precursors require high processing temperatures (>500 °C). Herein, we report the tuning of the decomposition profile (200-350 °C) of a range of octahedrally coordinated tris(β-ketoiminate) aluminium complexes of the type [Al(MeCN(R)CHC=OMe)₃ ], by varying the R substituents in the ligands. The complexes are derived from the reaction of trimethylamine alane (TMAA) and a series of N-substituted β-ketoiminate ligands (R-acnacH, R=Me, Et, ⁱ Pr, Ph) with varying R-substituents sizes. When the more sterically encumbered ligand (R=Mes) was used, the Al atom became five-coordinate, therefore representing the threshold to octahedral coordination around the metal in these type of compounds, which, consequently, lead to a change of decomposition profile. The resulting compounds have been characterised by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. [Al(MeCN(Me)CHC=OMe)₃ ] has been used as a single source precursor for the deposition of Al₂ O₃ . Thin films were deposited via aerosol assisted chemical vapour deposition (AACVD), with toluene as the solvent, and were analysed using SEM, EDX and XPS.

Dinuclear cobalt complexes supported by biphenol and binaphthol-derived bis(salicylaldimine) ligands: synthesis, characterization and catalytic application in β-enaminone synthesis from 1,3-dicarbonyl compounds and aliphatic amines

Biaryl scaffolding ligands form dicobalt clusters, which serve as efficient catalysts in enaminone synthesis under ambient conditions.

β-Ketoiminato-based copper(ii) complexes as CVD precursors for copper and copper oxide layer formation

The synthesis of ketoiminato copper(ii) complexes [Cu(OCRCHC(CH3)NCH2CH2X)(μ-OAc)]2 (X = NMe2: 4a, R = Me; 4b, R = Ph. X = OMe: 5, R = Me) and [Cu(OCRCHCMeNCH2CH2NEt2)(OAc)] (6, R = Me) from RC(O)CHC(CH3)N(H)CH2CH2X (X = NMe2: 1a, R = Me; 1b, R = Ph. X = NEt2: 1c, R = Me. X = OMe: 2, R = Me) and [Cu(OAc)2·H2O] (3) is reported. The molecular solid-state structures of 4-6 were determined by single crystal X-ray diffraction studies, showing that 4a,b and 5 are dimers which are set up by two [{Cu(μ-OAc)L}] (L = ketoiminato ligand) units featuring a square-planar Cu2O2 core with a distorted square-pyramidal geometry at Cu(ii). In contrast, 6 is monomeric with a tridentate-coordinated OCMeCHCMeNCH2CH2NEt2 ligand and a σ-bonded acetate group, thus inducing a square-planar environment around Cu(ii). The thermal behavior of all complexes was studied by TG (Thermogravimetry) and DSC (Differential Scanning Calorimetry) under an atmosphere of Ar and O2. Complex 4b shows the highest first onset temperature at 213 °C (under O2) and 239 °C (Ar). PXRD studies confirmed the formation of CuO under an atmosphere of O2 and Cu/Cu2O under Ar. TG-MS studies, exemplarily carried out with 4a, indicate the elimination of the ketoiminato ligands with detectable fragments such as m/z = 15, 28, 43, 44, 45, and 60 at a temperature above 250 °C. Vapor pressure measurements displayed that 5 shows the highest volatility of 3.6 mbar at 70 °C (for comparison, 4a, 1.4; 4b, 1.3; 6, 0.4 mbar) and hence 4a and 5 were used as MOCVD precursors for Cu/Cu2O deposition on Si/SiO2 at substrate temperatures of 450 °C and 510 °C. The deposition experiments were carried out under an atmosphere of nitrogen as well as oxygen. The as-obtained layers were characterized by SEM, EDX, XPS, and PXRD, showing that with oxygen as the reactive gas a mixture of metallic copper and copper(i) oxide without carbon impurities was formed, while under N2 Cu films with 53-68 mol% C contamination were produced. In a deposition experiment using precursor 5 at 510 °C under N2 a pure copper film was obtained.

Magnesium β-ketoiminates as CVD precursors for MgO formation

The synthesis and characterization of bis(ketoiminato)magnesium(ii) complexes of composition [Mg(OCR²CH₂CHR¹NCH₂CH₂X)₂] (X = NMe₂: 3a, R¹ = R² = Me; 3b, R¹ = Me, R² = Ph. X = OMe: 3c, R¹ = R² = Me) are reported.

Synthesis, characterization, and catalytic activity of sodium ketminiate complexes toward the ring-opening polymerization of l-lactide

Na complexes bearing ketiminate ligands revealed the greater catalytic activity and polymer controllability than that of Na complexes bearing Schiff base ligands.

Coordination of β-Ketoimine-Derived Ligands at Main Group and Transition Metals

The β-ketoimine HC[MeC(O)][MeC(NHt-Bu)] (1H) (Me = methyl) was used as a ligand in the synthesis of organo-aluminium and gallium compounds. With Al, the NH functionality was deprotonated to form the N,O-chelating β-ketoiminate ligand in Al{HC[MeC(O)][MeC(Nt-Bu)]}Me2 (3) (t-Bu = tertiary butyl), whereas the neutral form coordinated to trimethylgallium via the oxygen atom to form the adduct GaMe3·{HC[MeC(O)][MeC(NHt-Bu)]} (4). Reaction of 1H with Ar†NH2 (Ar† = 2-t-BuC6H4) afforded the new N-aryl β-ketoimine HC[MeC(O)][MeC(NHAr†)] (2H), which reacted with Pd(OAc)2 (OAc = acetate = CH3CO2–) to afford the heteroleptic dimer {Pd[HC(MeC(O))(MeC(NAr†))](μ-OAc)}2 ([5]2). The homoleptic bis(β-ketoiminate) Pd{HC[MeC(O)][MeC(NAr†)]}2 (6) was isolated as a minor product of this reaction. The crystal structures of compounds 3, 4, [5]2, and 6 are reported.

A closer look at ε-caprolactone polymerization catalyzed by alkyl aluminum complexes: the effect of induction period on overall catalytic activity

Previous studies on the ring-opening polymerization of ε-caprolactone using structurally related aluminum complexes as pre-catalysts showed inconsistent trends in the total conversion time.

Silica-supported Ni(II) complex bearing [O^N] ligand and copolymerization to afford silica hybrid polynorbornenes nanocomposites

In situ polymerization is an ideal technique to make a perfect dispersion of nanosilica into polymer matrixes. So, in this article, a novel silica-supported β-ketoamine nickel(II) dibromide precatalyst was efficiently prepared and used in in situ slurry polymerizations of norbornene (NB) to afford a highly productive NB addition polymerization system in combination with tris(pentafluorophenyl)borane (B(C6F5)3) cocatalyst. It exhibited productivity of 176.8 kg of polynorbornene (mol Ni)−1 h−1 at a mole ratio of B/Ni = 20, and the catalyst deactivation kinetics in the early stage of polymerization fitted well by the first-order deactivation kinetics up to about 60 min. The catalyst system was also effective for the copolymerization of NB and 5-norbornene-2-carboxylic acid methyl ester to produce the addition-type copolymers with high-molecular-weights (3.28–3.45 × 105 g mol−1) and incorporation rates (8.1–49.1%) as well as narrow molecular weight distributions (polydispersity index = 1.6). The nanoparticles were confirmed to be well-dispersed in the polymer matrix with each individual nanoparticle surrounded by polymer. Transparency of nanocomposites could be kept up to about 60%. The brittleness of polymer was obviously improved, and the tensile strength of polymer film could be as high as 47.8 MPa.