Catalytic metathesis of carbon dioxide with heterocumulenes mediated by titanium isopropoxide

The insertion of an isopropoxide ligand of titanium isopropoxide into heterocumulenes gives a product that carries out metathesis at elevated temperatures by undergoing insertion of a second heterocumulene in a head to head fashion, followed by an extrusion reaction.     

On the water promoted reaction of titanium isopropoxide with carbon dioxide

Insertion of carbon dioxide into titanium isopropoxide takes place only in the presence of trace quantities of water to give an isopropyl carbonato cluster which has been crystallographically characterised.     

Synthesis of TiC-C fiber from titanium isopropoxide treated phenolic resin fiber

Precursor fibers for titanium carbide-carbon fibers were synthesized by reacting phenolic resin fibers with titanium isopropoxide (TIP). In this system, titanium oxide gel coated fiber was prepared by hydrolyzing TIP infiltrated resin fiber. The precursor fibers obtained after the hydrolysis were converted into titanium oxide-carbon fibers (TiO₂-C fibers) by pyrolysis at 1273 K. The TiO₂-C fibers were converted into titanium carbide-carbon fibers (TiC-C fibers) by heat treatment at 1373–1973 K. The mechanisms of the conversion from TiO₂-C fibers to TiC-C fibers were characterized by TGA.     

Effect of titanium isopropoxide addition in low-temperature cured TiO2 photoanode for a flexible DSSC

In this study, titanium isopropoxide (TIPP) was employed as a binder for low-temperature processed photoanode of a flexible dye sensitized solar cell. The coating paste for dip-coating method was prepared comprising commercially available TiO₂ nanoparticles, TIPP and small amount of water. Effect of binder addition was compared at three different TIPP to TiO₂ nanoparticle molar ratios; 0.05, 0.1 and 0.3. By adding TIPP molecules directly to the coating paste, flexible photoanodes were successfully prepared. An optimum TIPP to TiO₂ particle ratio was selected considering the particle dispersion stability in the paste and the microstructure of prepared photoanode. The photoanode prepared using the paste with optimized composition showed highest photoconversion efficiency of 1.96 % from a unit cell.     

Electrochemical study of polyaniline deposited on a titanium surface

The electrochemical synthesis of polyaniline on a titanium surface in aqueous sulfuric acid solutions with various concentrations of added aniline has been investigated by cyclic voltammetry. By utilizing a more cathodic potential range (up to −0.6 V) for the cyclization than is usual (up to −0.2 V) on Pt and Au electrodes, the new voltammetric waves have been deconvoluted from the already well-known ones for polyaniline. By simultaneous electrochemical and in situ Raman spectroscopic measurements, the Raman bands of polyaniline electrodeposited on a Ti electrode, were assigned for potentials of −0.15 V and −0.6 V. It was found that the new monitored waves were closely related to the so-called “middle” peaks and appear only when the polyaniline reaches an overoxidized state. Received: 7 August 1997 / Accepted: 4 November 1997     

Asymmetric ring-opening of cyclohexene oxide with trimethylsilyl azide in the presence of titanium isopropoxide/chiral ligand

trans-2-Azidocyclohexanol of enantiomeric excess up to 24% is obtained in the ring opening of cyclohexene oxide by use of trimethylsilyl azide in the presence of stoechiometric amount of titanium tetraisopropoxide and chiral diols or aminoalcohols.     

Reductive ethylation of homoallyl alcohols with a disubstituted double bond with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide

Homoallyl and bishomoallyl alcohols with a disubstituted double bond treated with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide are converted into the products of a reductive ethylation of the olefin fragment. Under similar conditions esters of β,γ-unsaturated carboxylic acids undergo a successive cyclopropanation of the ester group and reductive ethylation of the double carbon-carbon bond and yield 1-(3-ethylalkyl)cyclopropanols. The features of the observed reactions are explained in the framework of the carbometallation mechanism of the double carbon-carbon bond by the action of dialkoxytitanacyclopropane reagents.     

Hybrid films based on hydroxylated castor oil and titanium(IV) isopropoxide

Novel organic–inorganic hybrid films were synthesized by the reaction of hydroxylated castor oil (HCO) with titanium(IV) isopropoxide (TIP) in which the mass proportions of organic to inorganic precursor varied from 95:5 to 85:15. Films were pre-cured at room temperature under an inert atmosphere and subsequently submitted to thermal curing. The macro- and microscopic properties of the films, including adhesion, hardness, microstructure (SEM and AFM) and thermal properties, were determined as a function of the proportion of HCO to TIP. Morphologic studies showed that the hybrid films were microscopically homogeneous. The hardness and tensile strength of the films increased, with increased concentration of inorganic precursor. All of the films exhibited good adhesion to an aluminum surface.     

Rhodium(II) catalyzed multi-component reactions of aryldiazoacetates with titanium(IV) isopropoxide and imines

Rh₂(OAc)₄ catalyzed diazo decomposition of aryldiazoacetates in the presence of titanium(IV) isopropoxide generated oxonium ylide intermediates. Trapping of the oxonium ylide intermediates with imines occurred subsequently via a nucleophilic addition. The three-component reaction of aryldiazoacetates, titanium(IV) isopropoxide, and imines gave α-alkoxyl-β-amino acid derivatives with C-N/C-C bond formation in a single step. Extension of the study to a four-component reaction with in situ generated imine was also investigated.     

Electrorheological behavior of the hybrid material prepared by cohydrolysis of titanium(IV) isopropoxide with minor additions of a liquid crystal

A new organic-inorganic hybrid material based on Ti(IV) dioxide and a liquid crystal of alkyloxybenzoic acid with variable-length alkyl chain was prepared by the sol-gel procedure. Physicochemical analysis of the resulting material was carried out, and the electrorheological activity and dielectric properties of the dispersions of the synthesized powders in polydimethylsiloxane (PMS-20) were examined in relation to the length of the alkyl chain of the liquid crystal.     

Enantioselective addition of organozinc reagents to ketones catalyzed by grafted isoborneolsulfonamide polymers and titanium isopropoxide

The catalytic enantioselective addition of different organozinc reagents, such as diethylzinc, or in situ generated phenylzinc derivatives to simple aryl methyl ketones was accomplished using titanium tetraisopropoxide and a polymeric ligand grafted with trans-1-phenylsulfonylamino-2-isoborneolsulfonylamidocyclohexane, to give the corresponding tertiary alcohols with enantioselectivities of up to >99% ee. Whereas the highest enantioselectivities were obtained in the ethylation process, the highest chemical yields were obtained in the phenylation process. The ligand could be re-used at least three times without any significant loss of activity.     

Reversible double insertion of aryl isocyanates into the Ti-O bond of titanium(IV) isopropoxide

The insertion of phenyl isocyanate into titanium isopropoxide leads to the formation of a dimeric complex [Ti(OⁱPr)₂(μ-OⁱPr){C₆H₅N(OⁱPr)CO}]₂ (1) which has been structurally characterized. Reaction of titanium isopropoxide with two and more than 2 equiv. of phenyl isocyanate is complicated by competitive, reversible insertion between the titanium carbamate and titanium isopropoxide. The ligand formed by insertion of phenyl isocyanate into the titanium carbamate has been structurally characterized in its protonated form C₆H₅N{C(OⁱPr)O}C(O)N(H)C₆H₅ (3aH). Insertion into the carbamate is kinetically favored whereas insertion into isopropoxide gives the thermodynamically favored product.     

Reaction of polyvinyl alcohol with aluminium isopropoxide

The uncatalyzed and oxalic acid catalyzed modification of polyvinyl alcohol (PVA) with aluminium isopropoxide have been studied for reaction in a suspension of powdered PVA in boiling benzene. Isopropyl alcohol (IPA) formed during the reaction was removed by continuous distillation of an IPA-benzene mixture. The reaction was initially quite fast but slowed up rapidly and practically stopped when only 4–12% of the OH-groups had reacted. Thermogravimetric analysis (TGA) showed that products with 6.8 mole A1/100 mole VA exhibit a significant rise in decomposition temperature from 250 to 285°. The characteristics are attributed to the occurrence of vicinal OH-groups in PVA.     

Chemical assembly of a titanium oxide layer on microporous silica

Russian Journal of General Chemistry - The chemical assembly of a titanium oxide coating on a regular microporous silica surface by the atomic layer deposition method was considered. The change in...     

Thermal stability of plasma deposited polysilanes

A new method for studying thermal stability and concomitant chemical composition changes on thermal treatment of thin polymeric films is presented. It is applied to the study of thermal properties and modification of properties of polysilane-like materials with variable dimensionality prepared by radio frequency plasma enhanced chemical vapour deposition (CVD). Structure and microphysical properties of these materials, modified by progressive annealing, are examined by fluorimetry, FTIR absorption spectroscopy and XPS. In addition, the role, bonding conditions and structural environments of organic moieties as well as their influence on thermal degradation processes are examined. It is found that plasma polysilanes undergo three consecutive thermal degradation processes: Si-Si bond cleavage, elimination of side groups and final carbide formation. Presence of disorder and crosslinking stabilises the plasmatic material in comparison to classically prepared polysilanes. Nanostructural units in low dimensional polysilanes enable the peak of the luminescence to be adjusted in the spectral range from near UV (360 nm) to red (600 nm).