Abstract: Preparation and characterization of three yttrium alkoxide complexes with new phosphasalen ligands are reported. The phosphasalens are analogues of the well-known salen ligands but with iminophosphorane donors replacing the imine functionality. The three yttrium alkoxide complexes show mono- and dinuclear structures in the solid state, depending on the substituents on the ligand. The new ligands and complexes are characterized using multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction experiments. The complexes are all rapid initiators for lactide polymerization; they show excellent polymerization control on addition of exogeneous alcohol. The mononuclear complex shows extremely rapid rates and a high degree of stereocontrol in rac-lactide polymerization, yielding heterotactic PLA (Ps of 0.9). The phosphasalens are, therefore, excellent ligands for lactide ring-opening polymerization catalysis showing superior rates and stereocontrol versus salen ligan...

Abstract: To investigate the excess hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium tetraisopropoxide using 6∶1 and 100∶1 H2O/Ti (r) ratios. The powders were dried and fired at a range of temperatures (⩽800°C). Hydroxylation and organic content in powders were characterised using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR), laser Raman microspectroscopy and elemental microanalysis; surface area and pore size distribution were evaluated using N2 gas adsorption; phase composition was analysed using X-ray diffraction (XRD) and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500°C. The powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an...

Abstract: The kinetics of polymerization of e-caprolactone (CL) initiated by aluminum-alkoxide complexes supported by the dianionic forms of N,N-bis[methyl-(2-hydroxy-3-tert-butyl-5-R-phenyl)]-N,N-dimethylethylenediamines, (LR)Al(Oi-Pr) (R = OMe, Br, NO2) were studied. The ligands are sterically similar but have variable electron donating characteristics due to the differing remote (para) ligand substituents R. Saturation kinetics were observed using [CL]0 = 2–2.6 M and [complex]0 = 7 mM, enabling independent determination of the substrate coordination (Keq) and insertion (k2) events in the ring-opening polymerization process. Analysis of the effects of the substituent R as a function of temperature on both Keq and k2 yielded thermodynamic parameters for these steps. The rate constant k2, related to alkoxide nucleophilicity, was strongly enhanced by electron-donating R substituents, but the binding parameter Keq is invariant as a function of ligand electronic properties. Density functional calculations provide atom...

Abstract: The polymer-to-ceramic transformation of a hafnium alkoxide-modified polysilazane was investigated via thermogravimetric analysis coupled with in situ mass spectrometry (TG/MS), nuclear magnetic resonance (MAS NMR) and transmission electron microscopy (TEM). The results indicate that the structural evolution of the polysilazane upon ceramization is strongly affected by the modification with hafnium alkoxide. Thus, the content of carbon in the ceramic backbone was relatively low, whereas a large amount of SiN4 sites and a segregated carbon phase was present in the sample. Furthermore, this study revealed the formation of a SiHfCNO amorphous single phase ceramic via pyrolysis of the polymer at 700 °C, whereas at higher pyrolysis temperatures precipitation of hafnia was observed, leading to an amorphous hafnia/silicon carbonitride ceramic nanocomposite. The precipitation of hafnia was shown to not rely on decomposition processes, but to be a result of rearrangement reactions occurring within the ceramic material.

Abstract: TiO2 nanoparticles were synthesised by a self-organization method using a continuous water vapour hydrolysis system without mixing. Formation of TiO2 particles was based on pure colloidal interactions of hydrolyzed alkoxide molecules generated at the interface between titanium alkoxide solution and water vapour. The effect of ethanol was proved to increase aggregation and packing of primary particles, leading to a significant size enlargement of secondary particles in a post annealing process above 500 °C. A new model to describe sol–gel TiO2 growth has been proposed, which considers the formation of secondary particles to be the result of nucleation of oversaturated primary particles, while the primary particles are the result of irreversible oligomerization of Ti oxo molecules.

Abstract: This study employed various polyol solvents to synthesize zinc oxide polycrystalline nanostructures in the form of fibers (1D), rhombic flakes (2D), and spheres (3D). The synthetic process primarily involved the use of zinc acetate dihydrate in polyol solutions, which were used to derive precursors of zinc alkoxides. Following hydrolysis at 160°C, the zinc alkoxide particles self-assembled into polycrystalline nanostructures with different morphologies. Following calcination at 500°C for 1 h, polycrystalline ZnO with good crystallinity was obtained. FE-SEM explored variations in surface morphology; XRD was used to analyze the crystalline structures and crystallinity of the products, which were confirmed as ZnO wurtzite structures. FE-TEM verified that the ZnO nanostructures were polycrystalline. Furthermore, we employed TGA/DSC to observe the phase transition. According to the results of property analyses, we proposed models of the relevant formation mechanisms. Finally, various ZnO structures were applied in the degradation of methylene blue to compare their photocatalytic efficiency.

Abstract: New ambient temperature liquid calcium alkoxides, [Ca(O(CH2CH2O)3CH3)2] (1) and [Ca(O(CH2CH2O)3CH2CH3)2] (2), together with [Ca(OCH2C(CH3)3)2] (3), were synthesised by reaction of ammonia-activated calcium with the appropriate alcohol. Their potentiality as stone consolidant products was investigated and compared with those of other alkoxides: [Ca(OCH2CH3)2(CH3CH2OH)4] (4), [Ca(OCH3)2] (5), [{Ca(OCH2CH2OCH3)2}9] (6), already described in the literature. Reaction of 1–3 with the atmosphere was studied, final products analysed and kinetic pathways investigated. The reaction produces CaCO3 and the vaterite/calcite ratios observed in the coatings generated from isopropyl alcohol solutions of 1–6 were found to considerably vary with the alkoxide precursor, which has a strong influence also on the morphology of the produced films. Furthermore, their efficiency as stone consolidants was tested by ultrasound measurements.

Abstract: We present herein a versatile and broadly applicable Fe-catalyzed regioselective alkoxy allylation of activated double bonds. Substituted allylic carbonates are converted into the corresponding σ-enyl Fe complexes by reaction with Bu(4)N[Fe(CO)(3)(NO)] (TBAFe) at 30 °C. The liberated alkoxide adds to an activated double bond with the generation of a C-nucleophile, which is trapped by the σ-enyl Fe complex in a regioselective manner. Alternatively, the alkoxide acts as a base in deprotonating an external pronucleophile, which undergoes Michael addition. The method is characterized by a broad functional group tolerance, mild reaction conditions, low catalyst loadings, and high regioselectivities in favor of the ipso-substitution product.

Abstract: Organic/inorganic polymer hybrids is a rapidly growing area of research because they offer opportunities to combine desirable properties of organic polymers (toughness, elasticity, formability) with those of inorganic solids (hardness, chemical resistance, strength). There are several routes to prepare hybrid materials, but one of the most common method is solgel technique generating inorganic phase within organic polymer matrix. The advantage of sol–gel technique is mild processing characteristics and the possibility of tailoring morphology of the growing inorganic phase and thus properties of the material by the subtle control of various reaction conditions. This process includes hydrolysis of the precursor (metal alkoxide) followed by condensation reactions of the resulting hydroxyl groups. Considering the nature of the interface between the organic and inorganic phases, hybrid materials can be categorized into two different classes. The first class corresponds to non-covalently bound networks of inorganic and organic phases. These hybrids show weak interactions between the polymer matrix and inorganic phase, such as van der Waals, hydrogen bonding or weak electrostatic interactions and can be prepared by physical mixing of an organic polymer with a metal alkoxide. In the second class organic and inorganic phases are linked through strong chemical bonds (covalent or ionic). Chemical bonding can be achieved by the incorporation of silane coupling groups into organic polymers [1-3].

Abstract: Cu-doped TiO2 was prepared by the refluxing of a mixture of copper and titanium alkoxides. The refluxing improved the Cu2+ dispersion in the TiO2 and formed effective Ti–O–Cu bonds. The impurity states due to the highly dispersed Cu2+ were presumed to trap the electrons in the conduction band of the TiO2 and prevent charge recombination of the electrons and holes. Consequently, the prolonged charge separation duration was suggested to enhance the photocatalytic activity of the Cu-doped TiO2. This enhancement was confirmed by the hydroxyl radical generation and organic compound degradation. The Ti–O–Cu bonds and electronic interaction between Cu and Ti should effectively promote the electron trapping. The Cu-doped TiO2 exhibited a visible light-induced activity due to the transition from the TiO2 valence band to the Cu2+ impurity states.

Abstract: Well-defined biphenol/binaphtolate group 4 alkoxide salt species [(Ph-Biphen-O)2M(OiPr)]Li(THF) (2a, M = Ti; 4a, M = Zr) and [(Ph-binapht-O)2M(OiPr)]Li(THF) (2b, M = Ti; 4b, M = Zr) were found to be readily accessible in good yields via alcohol elimination routes and/or substitution reactions from the corresponding pro-ligands Ph-Biphen-OH (1a) and rac-Ph-Binapht-OH (1b). As established via X-ray crystallographic analysis, the molecular structures of the Ti derivatives 2a and 2b consist of Li+ salts of anionic Ti–OiPr moieties in which the Ti center adopts a distorted tbp geometry and is effectively chelated by two biphenolate/binaphtolate units. Remarkably, the solution and solid state data for salt species 2a,b agree with the sole presence of one diastereomer (with a (Δ, aS, aS)/(Λ, aR, aR) configuration), thus indicating that formation of the Ti and Zr alkoxide complexes 2a,b/4a,b proceeds stereoselectively. In contrast, the neutral biphenolate/binaphtolate Zr complexes (Ph-biphen-O)2Zr(THF)2 (3a) and ...

Abstract: Carbonyl hydrosilylation catalyzed by (ArN)Mo(H)(SiH2Ph)(PMe3)3 (3) is unusual in that it does not involve the expected Si–O elimination from intermediate (ArN)Mo(SiH2Ph)(OiPr)(PMe3)2 (7). Instead, 7 reversibly transfers β-CH hydrogen from the alkoxide ligand to metal.

Abstract: The 2,2′-biphenyl-bridged bis(2-aminophenol) ligand 4,4′-di-tert-butyl-N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-2,2′-diaminobiphenyl (tBuClipH4) reacts with MoO2(acac)2 to form (tBuClipH2)MoO2, where the diarylamines remain protonated and bind trans to the terminal oxo groups. This complex readily loses water on treatment with pyridine or 3,5-lutidine to form mono-oxo complexes (tBuClip)MoO(L), which exhibit predominantly a cis-β geometry with an aryloxide trans to the oxo group. Exchange of the pyridine ligands is rapid and takes place by a dissociative mechanism, which occurs with retention of stereochemistry at molybdenum. Oxo-free alkoxide complexes (tBuClip)Mo(OR)2 are formed from (tBuClipH2)MoO2 and ROH. Treatment of NMo(OtBu)3 with tBuClipH4 results in complete deprotonation of the bis(aminophenol) and formation of a dimolybdenum complex (tBuClip)Mo(μ-N)(μ-NH2)Mo(tBuClip) containing both a bridging nitride (Mo–N = 1.848 A, Mo–N–Mo = 109.49°) and a bridging amide group. The strong π bonding of th...

Abstract: The synthesis and characterization of nine new heteroleptic alkoxides of niobium is described. Metathesis reactions of Nb2Cl10 with tBuCH2OH and pyridine (py) or 4-dimethylaminopyridine (DMAP) affords monomeric octahedral complexes Nb(OCH2tBu)5py (1) and Nb(OCH2tBu)5DMAP (2), respectively, in high yields (>60%). The same reaction with tBuOH resulted in a chloro functionalized alkoxide Nb(OtBu)4pyCl (3) and could not be pushed to complete removal of remaining Cl− ligand. The introduction of a chelating bidental ligand 3,3,3-trifluoro-1-(pyridine-2-yl)propen-2-ol (2-PyCHCOHCF3) (4′′) in the dimeric framework of Nb2(OiPr)10 (4′) produced a heteroleptic, monomeric niobium complex Nb(OiPr)4(2-PyCHCOCF3) (4) with significantly enhanced stability and volatility. As a comparison to (4), five different heteroaryl systems (5–9) with the same side chain have been synthesized and examined in order to understand the influence upon physio-chemical properties. All the new compounds (1–9) have been characterized by microanalysis, variable temperature multinuclear NMR spectroscopy, mass spectrometry, thermal analysis and single crystal X-ray diffraction studies ((3), (4) and (9)). The molecular structure of (3) revealed mononuclear species with Nb atoms present in the distorted octahedral environment of four tBuO, one chloride and one pyridine ligand. Compounds (4) and (9) consisting of four iPrO and a trifluoroheteroarylenolate exhibited a stronger distortion in the molecular geometry due to the rigidity of chelating β-alkenolate moiety.

Abstract: Here we report the synthesis and characterization of a stable suspension of modified titania nanoparticles. Phase-pure TiO2 nanocrystallites with narrow particle-size distributions were selectively prepared by hydrolysis-peptization of modified alkoxide followed by hydrothermal treatment. Autoclaving modified TiO2 in the presence of HNO3 as cooperative catalysts led to the formation of crystalline TiO2 with narrow-sized distribution. Following the hydrothermal treatment at 150°C, X-ray diffraction shows the particles to be exclusively anatase. Synthesized powder is characterized by FT-IR, scanning electron microscopy (FESEM) and transmission electron microscopy (HRTEM). The photocatalytic activity in the degradation of orange-II is quite comparable to good anatase and rutile nanocrystallites.

Abstract: Electron accumulation in TiO2 ethanolic sols prepared by the HCl hydrolysis of a titanium alkoxide has been scrutinized by UV–vis and EPR spectroscopy. Unexpectedly, Ti(III) centers, g = 1.9551, fo...

Abstract: The invention provides a preparation method for a nano-TiO2/organic silicon metal anti-corrosion coating. The preparation method is mainly characterized by comprising the following steps of: uniformly mixing titanium alkoxide, TTPO (Isopropyl Tri(Dioctylpyrophosphate) Titanate) and absolute ethyl alcohol at the normal temperature, slowly dropwise adding a mixed solution of the absolute ethanol, deionized water and an inorganic acid for stirring together, dropwise adding KH570, and continually stirring for reacting to obtain stable and transparent nano-TiO2 sol; uniformly mixing KH560, KH858 and absolute ethanol at the room temperature, slowly dropwise adding a mixed solution of absolute ethanol, an inorganic acid and deionized water, and continuously stirring for reacting to obtain an organic silicon precursor; dropwise adding the organic silicon precursor into the nano-TiO2 sol, and stirring for reacting at the normal temperature to obtain TiO2/organic silicon metal anti-corrosion coating sol; and plating a film on a metal surface in an anti-corrosion way by adopting means such as a spin-coating method and the like, and heating and curing at a low temperature. The method has the characteristics of simple and practical preparation process, low curing temperature, short curing time, and the like.

Abstract: The donor-functionalised alkoxides {Me(3-x)N(CH(2)CH(2)O)(x)} (L(x); x = 1, 2) have been used to form gallium hydride complexes [{GaH(2)(L(1))}(2)] and [{GaH(L(2))}(2)] that are stable and isolable at room temperature. Along with a heteroleptic gallium tris(alkoxide) complex [Ga(L(1))(3)] and the dimeric complex [{GaMe(L(2))}(2)], these compounds have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted chemical vapour deposition (AACVD) with toluene as solvent. The resulting films were mostly transparent, indicating low levels of carbon contamination, and they were also mainly amorphous. However, [Ga(L(1))(3)] did contain visibly crystalline material deposited at a substrate temperature of 450 °C, by far the lowest ever observed for the CVD of gallium oxide.